Marine Battery Banks & Over-Current Protection

A 300A (MRBF)Battery Terminal Mounted Fuse by Blue Sea Systems

In this article we will discuss fuse selection, fuse types, wire ampacity, Amperage Interrupt Capacity (AIC) and even potentially unsafe ABYC “exceptions to the rules”. In short, this article deals with why fusing your battery banks is a critical safety measure.

Bank Fusing Steps

1 – Know the amperage of the load you need to fuse

2 – Know the Ampacity of the wire you are trying to protect

3 – Determine the AIC of the bank you are trying to protect

The ABYC Standards – A bare Minimum not a Maximum

In regards to over-current protection of battery banks, owners should consider that the ABYC standards are a bare minimum requirement. In many cases, especially battery bank protection, certain aspects of ABYC E-11’s battery bank over-current protection should be considered as inadequate, potentially unsafe and below where a boat-owner should set their sights, if they want true safety. What the excerpt below is Saying is that any + conductor connected to a battery bank requires over current protection within 7 inches of the batteries positive terminal. This includes house banks, windlass banks, thruster & winch banks.

Your House Bank Requires over current protection!

Yes, I am an ABYC member, ABYC certified electrician and also part of the electrical sub-committee that helps develop these standards. Sometimes rational arguments made by the likes of Nigel Calder, myself and numerous others are over-shadowed in favor of taking a shortcut or to save boat-builders money. In many cases you can and should aim to exceed the ABYC standards. Specifically with regard battery bank fusing or sheathed/loomed or conduit protected wire.

Definitions Used:

Ampere Interrupting Capacity (AIC) – the maximum short-circuit current that an over-current protection device can safely interrupt under standard test conditions.

Source of Power – In regards to battery bank over-current protection the battery bank is the “source of power” that we are protecting the wires from.

Conduit – an enclosure that is part of a closed wiring system for insulated conductors and/or cables in electrical installations, allowing them to be drawn in and/or replaced. Conduit or sleeving also serves to protect from chafing and shorting.

Equipment Enclosure – the outside shell of equipment that provides personnel protection from electrical hazards, burns, rotating machinery, and sharp edges, and provides protection to the device from mechanical damage or weather.

Ignition Protection – the design and construction of a device such that under typical design operating condition, will not ignite a flammable hydrocarbon mixture surrounding the device when an ignition source causes an internal explosion, or it is incapable of releasing sufficient electrical or thermal energy to ignite a hydrocarbon mixture, or the source of ignition is hermetically sealed.

Loom – a flexible covering designed to protect conductors.

Main Over-current Protection Device – an over current protection device with no other over current protection between it and the source of power.

Pigtails – provided conductors integral to an electrical component or appliance for the purpose of connection to external circuits. eg; LED navigation lighting.

Self-limiting Device – a device whose maximum output is restricted to a specified value by its magnetic or electrical characteristics.

Sheath – a material used as a continuous protective covering, such as overlapping electrical tape, woven sleeving, molded rubber, molded plastic, loom, or flexible tubing, around one or more insulated conductors.

A battery bank fuse is there to protect the wire!

The ABYC Standards on Battery Bank Fusing:

Fuse Location:

The ABYC requirement is for a battery bank fuse is to be within 7 wire inches of the battery bank. The European ISO/RCD (which is law) requires the fuse be within 200mm. 200mm equates to about 7.9”. In this regard, the European ISO/RCD is essentially the same as the ABYC’s 7” requirement. The difference here is the ABYC standards are still voluntary. I only point this out because we hear time and again that the ABYC is not a law, and it is not, but the ISO/RCD (recreational Craft Directive) is a law.

These fuses, one for each bank, are in compliance with ABYC E-11. The one on the cranking battery exceeds and goes above and beyond the ABYC standards.

In the real world of boats and battery compartments meeting the 7” rule is not always as easy as it sounds. If you can’t get within 7″ then the next best thing is to be as close as possible but the wire should always be in a protective conduit or flexible loom, once the jumper to the fuse exceeds 7″.

If you’re having trouble meeting the 7″ rule, the Blue Sea battery terminal fuses shown in this photo are an excellent option for up to 300A. If trying to fuse a bank that may ever need to be used to start a bigger engine, you may need a Class T or ANL fuse and the correct fuse holder..

These fuses are excellent but they do add nearly 2″, in height, to a battery post, if vertically mounted so measure your battery compartment height carefully.

Exceptions to the 7” Rule:

While the standards do have an allowable exception for over current protection regarding cranking conductors. Nowhere in the ABYC standards does it suggests not fusing cranking conductors. In other words, the ABYC is not saying “don’t fuse a creaking conductor” they’re simply allowing you an exception to the rule if your engine is too big to be fused.

It is quite often repeated as fact on the Internet, by folks who don’t understand what they’re talking about, that the ABYC says “don’t fuse engine cranking conductors”. The standards say no such thing.

Other Exceptions to the 7” Rule:

Under ABYC E-11 the fuse does not always need to be within 7”. Depending upon the location & where the wire connects to, meaning the battery or other source of power, such as a battery switch, and when “contained throughout its entire distances in a sheath, or enclosure such as a conduit, junction box, control box, or enclosed panel” the fuse can be either at a maximum distance of 40” or 72”.

72” Exception to the 7” Rule:

40” Exception to the 7” Rule:

“Exceptions” to Bank Fusing – Do They Always Make Sense?

Remember above where we mentioned that the ABYC standards are a bare minimum and you can often do better? Well, exception #1 “cranking conductors is one area where the ABYC is simply leaving far too much room for dangerous installations.

In today’s day and age you can, and ideally should, strive to achieve better than the extremely low bar set by ABYC E-11 on bank fusing. Compass Marine inc. has been fusing cranking conductors since the mid 90’s and these circuits have likely undergone hundreds of thousands of engine-starts. I can count on two fingers the number of nuisance trips we’ve had.

#1 An engine that hydro-locked due to a scoop strainer installed with the scoop facing forward. (darn good thing the fuse tripped)

#2 A boat that tangled in lobster gear and the reversing gear was stuck in gear. The owner tried to start it anyway. (Again, it’s a darn good thing the fuse tripped.)

Sure, using the “cranking conductor” exception is an easy mark for a boat builder, as it saves them money, but many of us who do this for a living find this exception to be patently unsafe without also mandating the cranking conductors be located in a protective conduit/sleeve. Nigel Calder is one such individual who also believes this exception is not one to use (see excerpts below).

The argument a few of the members of the ABYC committees make is that starting motors draw too much current and are difficult to fuse. Ok, if this is the argument, why don’t we take a look at devices such as DC powered bow thrusters. A bow thruster is not a cranking conductor so by the ABYC standards that connection to the thruster bank must be fused.

This series wound thruster motor is exactly like a typical marine engine starter motor. The only difference is that it actually draws a lot more current, and for a lot longer, than you’ll find on the vast majority of marine engines.

The difference between a starter motor and a thruster are however huge. A typical engine starting duration ranges from about * 0.75 seconds to 1.5 seconds on average(*data Midtronics EXP 1000HD) . Bow thruster motors are rated for as much as 3-5 minutes and many owners use them for 30 seconds or more at a blast. The bottom line is this; a bow thruster is treating a fuse in a much more abusive manner than a starter motor ever will! The ABYC requires the bank feeding this bow thruster to be fused but not starter motors? This is about as nonsensical and hypocritical as your everyday politician( either side of the aisle, your pick)!

This particular bow thruster draws well over 1000A for in-rush, and physically maxes out our Fluke 376 which can measure to 1000A DC for in-rush. Under actual thrusting loads it typically pulls 330-365A, for as long as 30 seconds or more at a time. On land, with no load/water to move, it draws about 285A +/- which is pretty much spot-on for the motors 376A rating. Also keep in mind this is not the biggest 12V thruster we deal with.

“But, the motor says 3kW what about Ohm’s law?”

3 kW = 3000W If we take a typical no-load rating of the motor this is; 3000W/11.5V = 261A

11.5V is a perfectly acceptable voltage sag on a bow thruster bank under that type of load. However, as I mentioned, this is a “no-load” rating meaning no gears to turn, propeller to spin or water to move. This is how and why a 3kW motor can typically draw much more current than the face value 3kW rating.

“But, the rating plate says 376A, why does it disagree with the 3 kW rating?”

Yes, the rating plate may say 3kW and 376A but the motor wattage rating is a no-load rating. Put a load on any DC motor and it will draw more power than the no-load wattage rating indicates. See chart below.

One more example:

This is the current spec from an Anderson Electric Winch we installed. The ABYC requires these winch batteries to be fused. Notice how high the in-rush is (green square)?

And here is a chart showing the winch current draw based on winch load. As stated, apply a load to an electric motor and it will draw more than its face value rating.

The point in all this discussion on bow thrusters and electric winches is to examine why mandating over-current protection for DC bow thrusters/winches and then making “exceptions” for engine starting motors is actually pretty silly..

What would make a cranking conductor fuse exception ok?

A fuse exception would be OK if the ABYC actually mandated un-fused cranking conductors to be protected in a protective sheath, conduit, sleeve etc. like the 40” and 72” rules do, but the standards do not call for this. Unsleeved/unprotected wire is perfectly fine for a cranking conductor under ABYC E-11. Crazy? You Bet bet is!

What AWG do manufacturers suggest for cranking conductors?

Here are some minimum manufacturer suggestions for battery/starter cable from Westerbeke and Universal.

Universal / Westerbeke minimum wire size requirements (wire length round-trip)

2 AWG = 8′
1 AWG= 10′
1/0 AWG = 14′
2/0 AWG = 18′
3/0 AWG = 22′
4/0 AWG = 28′

Nigel Calder addresses the fusing of cranking conductors in his books;

Begin Quote – Nigel Calder:

End Quote:

and

Quote Nigel Calder:

End Quote:

A real-world example of why this exception can be dangerous.

Exceptions to the Rule vs. Common Sense

In August of 2010 a local yacht clubs junior sailing program had a chase boat returning to the dock with a few 8-10-year-old junior sailors, and their coach. They were aboard a well maintained 15’ Boston Whaler. As they tied up to the dock, the battery cables under the helm seat started to smoke. Within seconds the entire boat was engulfed in flames. The boat was a total loss. The kids barely made it off the boat before the fire fully engulfed the vessel.

Points to Consider:

• The ABYC standards do not even require a battery switch let alone a main bank fuse for this boat!
• This tiny Honda outboard is very, very easy to fuse with an MRBF battery terminal mounted fuse!
• This boat fire was driven by a single group 27 battery, into shorted 6 GA wire!

What if this happened when the kids & coach were out on the bay, not as they approached the dock? Safe? Hell no!

If a single G-27 battery can do this to the Honda outboards factory supplied wire, & this boat, what do you suppose two 8D cranking batteries will do to your wire & boat if the wire shorts?

A small MRBF fuse holder & fuse, that costs $30.00, would have 100% prevented this fire.

The bank below is capable of 18,000A of short circuit current!

The installer put the wires in protective loom and went above and beyond what the ABYC requires. Smart guy!

Fuses Work!

Below is an example where the owner’s boat was protected by a fuse. This owner had a 1/2/B switch and decided it would be a good idea to fuse both banks. A year after doing this DIY upgrade he had a plastic wire-tie fail and the large gauge battery cable came in contact with the engine.

The 300A fuse, that was protecting this wire, saved this owners boat from burning to the waterline.

Foolish to not protect all batteries with over-current protection or a protective conduit? You bet it is!

Bare Minimum Fuse Sizes

Let’s cut-to-the-chase on this. Below are the minimum bank fusing we prefer to see for any bank that could ever be called upon to start a motor. If your vessel has a 1/2/B switch both banks need to be capable of starting the engine.

Bare minimum fuse size for small diesel engines 8HP to 25HP = 250A

Bare minimum fuse size for medium diesel engines 25HP to 60HP = 300A

Above 60HP 75% of measured *inrush current as minimum fuse size.

*You will need a clamp meter such as a Fluke 376, or equivalent, to measure the inrush.

If you follow the above guidelines, you will not suffer “nuisance trips” if fusing your starting bank.

If your engine is too large for a fuse put the entire length of the cranking conductor in a protective conduit or protective loom! Unprotected battery cables are a fire waiting to happen!

Selecting the Proper Type of Fuse:

Battery banks larger than 255Ah should be protected with fuses not breakers. The following types of fuses are suitable for main bank protection:

ANL

CLASS T (preferred for Li-ion& large AGM Banks)

MRBF

These fuses are available from Blue Sea Systems and other reputable sellers. They should however be “Ignition Protected” fuses if installed on a gasoline boat and Blue Sea Systems is the only one I know of offering ANL fuses with ignition or spark protection for ANL’s. Class T fuses are not technically IP rated however they are fully encased in a metal body. Class T fuses have simply not been tested for IP rather than do not meet IP. In speaking with Blue Sea systems I was told they have no documented cases of an IP breach on any Class T fuses.

Remember, the main battery over current protection (OCP) or over current protection device (OCPD) is sized to protect the wire. The main bank fuse is not there to protect the down-stream equipment. Those fuses would be located after the main bank protection fuse. This is often misunderstood.

You can always go smaller with OCP than the wires ampacity rating, but ideally should not exceed the ampacity rating unless you are fusing the battery bank and the bank could potentially be called upon to crank a motor. The main bank fuses are there to prevent the wire from overheating, melting and starting a fire in a dead short situation. Generally speaking a fuse is sized to not exceed the maximum ampacity of the wire. In certain instances the ABYC allows for up to 150% of the chart below.

What if my engine draws more than the wiring is rated for?”

Nigel Calder clearly addressed this above and this is actually not uncommon at all. Many builders undersized starting wire for many years, and got away with it, due to the short-duration starting circuits are physically current-loaded for. Today, most builders have come up closer to where they should be for wire ampacity.

A good example of this is the original Universal M-25 as shipped on Catalina Yachts in the 80’s and most of the 90’s. Catalina used to ship the Universal M-25’s with 4GA battery wire. In the late 90’s they began shipping the same engine, a Universal M-25XPB, with 2/0 gauge wire. Going from 4 AWG to 2/0 AWG is a huge improvement. If you have small gauge wire, an upgrade to larger wire can be a very good investment. Your engine will also start quicker and the starter will see a lot less voltage-drop. Larger wire means you’ll be able to develop more cranking current for faster starts. Nearly every sailboat I went aboard during the last boat show, including a tailerable 28 footer, was using 1/0 or larger wire with 1/0 and 2/0 being the most popular in boats over 30′.

Won’t the starters in-rush current blow my fuse?

First, let’s identify what in-rush current really is? In-rush current is the very brief spike in current that the starter undergoes to get the motor to begin turning over from a stopped state. The in-rush duration is usually about 100ms to 300ms long, and is not long enough to blow a properly sized fuse. ANL, MRBF or Class T fuses are not sized for the inrush, they are sized so they don’t nuisance trip when cranking an engine.

Compare the in-rush duration to a fuse rated for main bank protection and it becomes clear as to hoe this is so.

ANL FUSE- TRIP DELAY CURVE

CLASS-T FUSE -TRIP DELAY CURVE

MRBF TRIP-DELAY CURVE

Contrary to popular misconception fuses don’t always trip at their face value rating. You also need a long enough duration at high current. As can be seen above, each fuse has a trip-delay curve. These curves are from Blue Sea Systems.

If you look closely, a 300A Blue Sea Systems ANL fuse can support 600% of its rating, or nearly 1800A, for approximately 0.5 Seconds. The inrush duration is not this long.

If we look at the trip-delay curves above it becomes quite clear that ANL, Class-T or MRBF do not trip at face value unless the duration of high-current is long enough.

For example, a 300A Blue Sea Systems ANL fuse can handle 300% of its rating for an entire second or 900A. Peak cranking currents just don’t last this long. If we look to the far right of the trip-delay graph you can see that it would take nearly 500 seconds or 8.3 minutes at 150% of the ANL fuses rating to actually trip. For a 300A fuse this is 450A for as long eight minutes or so. This is the reason why fusing cranking circuits is not the problematic concern some make it out to be. You just need to size the fuse correctly.

300 AMP ANL Seconds vs. Trip-Amperage

.7 Seconds =1800A
1 Second = 900A
5 Seconds = 500A
500 Seconds =450A

AIC & Why It’s Critically Important!

AIC stand for Amperage Interrupt Capacity. The AIC is sometimes called “interrupt capacity”too. AIC is the short circuit amperage capacity the fuse or breaker can “interrupt safely” without welding shut, blowing up and losing “ignition protection” or jumping the gap and failing to provide protection..

The ABYC Standard

The green arrow is pointing to a specification that can only be met by a Class T fuse!

Table 3B below.

Not All Fuses/breakers are Created equal!

Not all fuses/breakers are created equal. Always Stick with fuses by Blue Sea Systems, Cooper Bussmann or Littlelfuse.

When ordering from less than reputable sellers make sure the products can meet the following;

Avoid purchasing fuses/breakers off of Scamazon! The customer below learned a very hard lesson. The pictured breaker came from Amazon and the customer certainly got scammed! The 200A breaker was consistently tripping every time his alternator output got to 85A! Amazon refused to publish his review on the product! The alternator load dumps caused his alternator to fail and also took out his brand new B&G plotter!

And here’s a guy who’s budget breaker welded itself shut! This is why AIC Matters!

*Images below courtesy Attainable Adventure Cruising

The welded & melted breaker

Below is another example of why AIC maters. The fuse below was attached directly to the battery + terminal and when it tripped it failed in a manner that it kept allowing current to pass. The owner noticed a fumy smell and it was his bilge pump starting to melt.!

The meter is still showing continuity even though the fuse clearly tried to blow! The AIC rating of the fuse maters!

The above ATC Fuse only had an AIC of 1000A yet was directly connected to a bank of AGM batteries that could deliver 20,000A of short-circuit current

ATC Fuse AIC

What Fuses have an AIC that is suitable for a cruising boat bank?

Class T, ANL and MRBF fuses all have an AIC that can be suitable for house banks. If you have a large bank of AGM or Lithium batteries then a Class T fuse is the best fuse to meet the AIC requirements. For LiFePO4you really want to use class T. ABYC E-13 specifically calls this out.. The AIC rating of Class T fuses is 20,000 amps at 125V. It is significantly higher at 12V but Blue Sea Systems has not run the AIC tests at 12V. A 20,000A rating at 125V is a very, very impressive AIC rating. The Class-T fuse is the most robust fuse we use in the marine environment because it is fully metal encased.

ANL fuses have AIC of 6000A at 32V and MRBF fuses are 10,000A at 14V.

What about Breakers & AIC?

The concern with AIC & breakers is that breakers can literally weld shut before tripping, if the bank has enough short-circuit current behind it. For smallish house battery banks, you ideally want an AIC rated fuse or breaker of 5000A AIC or greater. Even Blue Seas Best class of breaker, the 187 series is only rated at 5000A AIC.

Just one group31 Odyssey TPPL AGM is capable of 5000A of short circuit current! Please understand that AIC is not just for large AGM banks or LiFePO4 batteries. A single 100Ah Group 31 Odyssey AGM battery can deliver 5000A of short circuit current into a dead short. A 200Ah bank of Group 31 Odyssey AGM batteries is 10,000A into a dead short. This is why the AIC rating of the over-current device is critically important.

The actual ABYC requirement for batteries is that any bank over 255Ah needs 5000A AIC rated protection or greater.

Cheap Fuses have no place on your boat

For the ABYC Li-Ion Battery sub-committee I spent A full day blowing all types of fuses and one thing that was seen very early on is that all fuses are not at all created equally. When a fuse trips it needs to trip in a safe manner. Knock of fuses, often found on the internet for car stereos, etc. are not built to the same standards as fuses from the likes of Blue Sea Systems, Littelfuse or Cooper Bussman. With a quick phone call any of these three companies you can quickly get all the testing data for any products they sell. Go ahead and try that with off-brandfuses/breakers you find on Amazon I know what the answer will be, we tried to do it for one of our customers who had a Scamazon breaker blow up one of his alternators. It tripped at just 110 A and was rated 250A! Sorry, no, this is not covered under warranty!

Blue Sea Systems ANL fuses have an IP rating “ignition protection” which is important on boats as the fuse must fail/trip safely so as not to ignite any on-board fumes. In the image below we have a bunch of cheap Amazon ANL fuses. A Blue Sea Systems ANL is built with G10 fiberglass sheet, features four rivets holding it together and uses a very durable Mica window. The cheap ANL fuses are a plastic body, two rivets and they use thin plastic windows that are prone to blow out when the fuse trips. We tripped 22 of these cheap fuses and the windows failed unsafely 20 out of 22 times. You can see the blown-out window in this image. When in doubt stick with fuses and fuse holders from Blue Sea Systems, Littelfuse or Cooper Bussman.

The photo below is a prime example of what can happen to a cheap ANL fuse. These claimed to be “ignition protected” (IP) and AIC rated fuses. After multiple emails to the vendor, they failed to provide any documentation to back any of these claims up? When buying fuses on Amazon it is certainly buyer beware! A few weeks later I noticed the specifications had magically changed and they no longer claimed IP or an AIC rating. Sadly, the only data I was able to find on the fuses was “Made in China“.

The fuses below were connected directly to a LiFePO4 lithium battery bank and then the circuit was shorted. The fuse trip was so violent, it literally blew the windows out of the fuses. This is an UNSAFE failure mode for a fuse. It failed for both AIC and ignition protection safety.

What About Victron Lynx Distribution Buses?

Victron has a beautiful line of distribution busses called the Lynx series. The Problem with these busses is they employ MEGA fuses that only have a AIC of 2000A. The solution is quite simple. You simply feed the distribution bus with a fuse that has the correct AIC Rating for the battery bank.Once the mega fuses  are behind the main distribution fuse, a fuse that has the correct AIC rating, the MEGA fuses are now fine.

The Solution:

Pro Tips:

If you lack battery compartment height, and your batteries have lead posts, a military post can get you horizontal with an MRBF.

MRBF fuses work really well mounted to busbars

ANL or class T fuses/holders can be bussed together using copper bar stock from McMaster-Carr

Fuse Safely!!

If you’ve read my articles for any period of time you probably realize that there are a few things that I can’t stand;

#1 well marketed products that actually suck in reality.

#2 Pop-up brands ( pop-up brands =companies that never existed before Amazon) that slap their sticker on the cheapest Chinese products they can find and then market them as a reputable brand.

Things I Like;

#1-manufacturers who aren’t afraid to step out on a limb and go so far above and beyond what the rest of the industry is doing that it makes the competition look like they’re stuck in the 1940s. Victron does that with these chargers.

Sadly, the portable or maintenance/”trickle” charger market is flooded with products that are stuck in the 1940’s. Most of them I wouldn’t charge a $25.00 U1 garden tractor battery with.

My dad’s whole adult life was spent as an antique car collector. Most of these cars sat for months and months and months without any use. So, over the years my dad collected a massive pile of trickle chargers or maintenance chargers as some of these companies like to call them . Every single one of them, that we recovered from his barn after he passed away, is the biggest piece of crap I’ve ever seen. I now understand why my dad replaced batteries so often. The chargers he was buying were pure junk.. His collection included brands such as the well-known “Battery tender”, Schumacher, Duracell, NOCO, Diehard, Harbor freight, Guest, Century, and even one that was stickered by John Deere.

A number of years ago one of our wholesalers took on the NOCO line. It was marketed as the second coming of Jesus. I bought a bunch of them to maintain customers batteries over the winter only to find out they do no such thing. They turned off after the battery has been charged and then they go to sleep/turn off. They do not do a float stage. When the charger turns off the battery then self discharges and can start to sulfate.

All in all I bought three or four of these NOCO “chargers”. I know, I know, I failed to do enough research before pulling the trigger! I just bought them based on the introductory price and you guessed it the glossy marketing. Stupid me!! After realizing how bad these chargers were I, took about three or four of them up to our camp where they wound up charging the Kubota tractor the plow truck, a couple of old vehicles we have up there, ATV’s, snowmobile’s etc. Over the winter we threw one of the NOCO’s, a G3500 on the plow truck. It’s a Ford F550 diesel. When it finally snowed and we went out to start the truck all it did was make a “click, click” …The battery charger was still on and the light was solid green indicating it was ready to go and the battery state was at 100% No such thing, the batteries were at 11.6 V before we even tried to start it. The charger was still saying they were perfect and sitting at 100% SoC. Click click click….. We wound up having to replace the batteries on the plow truck thanks to that well marketed NOCO charger. Since our debacle with the NOCO chargers, Victron launched its new series of IP 65 and IP 67 chargers. The NOCO’s up at camp, and here in my shop, have all been replaced by Victron chargers.

Let me sum this article up in one line for you:

There is no need to invest in any maintenance or portable charger other than the VICTRON Blue Smart IP 65 OR IP 67’s!

The entire point of this article is to get you to stop buying crappy chargers, as I did, that are marketed as the second coming of Jesus when they are far from it. For this article I spent hundreds of hours testing the 5 gal bucket full of portable charges my dad had, including the NOCO chargers that we had. None of these chargers were worth the cost of the orange 5 gallon Home Depot bucket I had them in, yet some of these chargers cost as much as $150 or more. Some of these chargers were so bad they only charged the battery to 13 V and then stopped at that point. You cannot charge a battery without hitting an absorption voltage and do so in a healthy manner. Some of the chargers, such as the NOCO would charge to an absorption voltage then shut off completely with no float whatsoever. One of the NOCO’s would not turn back on until the battery bank got down to about 12.52 V. The other one I had allowed the battery bank to fall all the way to 11.6 V and it never turned back on. This is the charger that killed the batteries on the F550.. NOCO swears this cannot happen yet it did and my Fluke meters are NIST calibrated..

The key to understanding some of these “well marketed” chargers is this:

As can be seen below, from a support chat with NOCO, their chargers do not float charge the batteries. This one charges to 14.5V then turns off and waits for the battery voltage to drop to 12.7V. It then repeats the 14.5V>drop to 12.7V repeat>repeat.. Apparently, I got two defective chargers that need to be sent back? What are the odds of that?

Definitions:

Trickle Charger – a trickle charger is a charger that puts out a constant-current and has no voltage regulation. A true trickle-charger should never be used on lead acid batteries and be left unattended. Lifeline battery goes so far as to prohibit the use of trickle chargers.

Maintenance Charger-a charger that is supposed to bring the batteries to an absorption voltage and then drop to a float voltage. Throughout this testing we discovered that this definition is not adhered to by most of the manufacturers marketing and selling “maintenance chargers”.

Smart Charger- a charger that does multiple stages of charging; Bulk, absorption and ends with a float voltage.

The Victron Blue Smart IP65 & IP67 Chargers

The Victron Blue Smart and IP 65 and IP 67 chargers are by far the best small amperage chargers you will find at any price, yet they are very reasonably priced. These chargers cost less than some of the other so-called “maintenance” chargers out there, yet they do far more and feature full custom programmability.. They’re also covered by a five year warranty!

The BlueSmart IP65 chargers (water resistant) are available in 12V- 5A, 7A, 10A & 15A + 24V 5A & 8A.They are available in both 120V (North America) and 230V models.

B

One of our IP65 12V 5Achargers set up to maintain a Firefly Carbon Foam Battery.

like many Victron products the IP 65 and IP 67 chargers are Bluetooth compatible. These chargers can be custom programmed to charge any type of battery you wish to charge including LiFePO4. All you need to do is download the Victron connect app.

When you open the app your charger should show up in the device list. If you have multiple chargers, as we do, you can name each charger. As can be seen from this list my phone is seeing three of our Victron IP65 chargers. One of the chargers is set up to charge firefly batteries. One of the chargers is set up to charge Lithionics and one of them is just named charger #2

Another cool feature of the IP 65 and IP67 chargers is that you can run them in power supply mode or in battery charger mode. It can run as either a multistage battery charger, or a power supply, it’s your choice.

This is the main page of the app. To change anything you simply click the gear icon as pointed to by the green arrow.

Once you click the gear icon you will land here. In the section with the red box you can choose any one of Victron’s pre-defined programs or a custom saved program of your choosing. You can also select full amperage , in this case 5A, or a slow 2A charge for smaller batteries.

For Custom Programming you toggle at the green arrow;

Once you click “Advanced Settings” You will get a Lawyer warning;

On the next page you select “User Defined” then click on “Expert Mode”.

Next we’ll set the absorption voltage by clicking on the absorption voltage line;

Next you set your absorption voltage by using the + & – arrows and selecting OK. Yes, you are seeing that correctly. Victron allows you to adjust voltages to the hundredths position! If you want to set it at 14.67V instead of 14.6V, go right ahead. This feature alone is enough to keep all the other chargers back in the 1940s..

Repeat the same steps for setting the float voltage. Please note that Victron actually treats you like an adult and allows you to either enable or disable the entire float stage. Your Choice! For the Firefly AGM I have set float to 13.4V.

These are the other parameters that can be set;

What the Heck is “Storage voltage”?

In one of my articles from 2010 LiFePo4 batteries on Boats, I go into great detail about how LiFePo4 batteries cannot be charged like lead acid batteries. Float charging LiFePo4 batteries is not necessarily good for them. They prefer to be stored long term at about 50% state of charge and not be left on permanent float. I discussed how we we need to have different terms, float voltage and storage voltage. Well, wouldn’t you know Victron is the first to do so & it’s brilliant. Even though this is a Firefly battery, the inventor of these batteries Kurtis (a Fellow Mainer) preferred to see them at 13.2 V maximum for float voltage. So, I was able to set a short float of 13.4V which is what the North American importer says is okay. Then after 13.4V, it drops down to a 13.2V storage voltage. There is no other charger manufacturer that allows you to set a storage voltage!

So, How Does The Custom Programming work?

For this testing I chose to use our fluke to 289 set for voltage data logging. I didn’t realize it at first but it was set to capture once each second. This makes for a huge .CSV file. Nothing Excel couldn’t handle, of course. Note the accuracy of the absorption voltage which had been set to 14.4V!

This is what our custom programming looked like;

As can be seen the Victron BlueSmart IP65 performed exactly as it was programmed. With the new Victron IP 65 and IP 67 chargers there is absolutely no reason on earth to purchase anything else. You get what you paid for…

Accessories

Victron even offers some cool accessories that are also reasonably priced.

While the ring terminal plug and quick-clips come with each charger they are also available separately.

FAQ

Q: Can I permanently mount these chargers?

A: Yes, these chargers can be permanently mounted and they have four mounting holes specifically for this purpose. Any permanent mounting must be done to Marine safety standards including a fuse in the battery positively than 7 inches of the battery and all other protocols followed. the IP 65 charger needs to be mounted in a dry area just as you would with any dry mount charger. When permanently mounting these chargers will need to use the ring terminals not the alligator clips.

Q: Do these chargers meet the safety standards?

A: Both theBlueSmart IP65 and the IP67 chargers are UL 1236!

Q: I have a Victron Orion TR Smart and it runs hot How hot do these chargers run?

A: Both the IP 65 the IP 67 are incredibly efficient chargers. To test this out I discharged a 125 amp hour Lithionics LifePo4 battery to 0% SOC and set one of our IP65 chargers to 5A and let it go. After 20+ hours of continuous bulk charging the charger was barely warm to the touch. There are many chargers in this size range would have burned themselves up trying to tackle this.

Victron IP65 & IP 67 Wish List/Shortcomings:

#1: when these chargers are set to run at their full amperage, there is slight voltage drop between the charger and the batteries. They really need to make these chargers compatible with the Smart Battery Sense which would provide battery temperature and battery voltage data over Bluetooth.

#2 There are many lithium iron phosphate batteries out there that require an absorption duration that is shorter than one hour, the current minimum. This is a simple programming change that many of us in the industry have been asking for for Since these charges were launched. I don’t know why Victron has not been able to do this?

#3 No US 120V 6V charger in this line-up.

Pricing:

I should not need to mention this but I will. Always buy your Victron components from a reputable dealer, preferably one who also installs Victron components or who can provide you tech support. Big online monster retailers do not provide any support. You can usually tell the dealer is an upstanding legitimate veteran dealer because they abide by Victron’s MRP. If you find pricing on any of these chargers that is below what you see here ,walk away from the dealer! They are either a gray market dealer or adealer who is not abiding by Victron’s strict policies. If they are willing to circumvent their dealer agreement they’re willing to screw you too.

Blue Smart IP65
12V5A=$89.25
12V7A=$116.45
12V10A=$138.55
12V15A=$159.80
Case for IP65 $28.05

Blue Smart IP67

12V7A =$111.35
12V13A =$131.75
12V17A =$144.50
12V25A =$211.65

Lead is Dead (almost)

You may be wondering why I am saying lead is dead ?The answer to that is simple; lead acid battery makers dug their own graves by grossly misleading the general public. They know damn well none of these batteries will never meet the cycle-life claims out in the real world whwere PSoC use is a reality. Why? Because the real-world is not a white coat white glove laboratory and in the real world “sulfation-happens”.

Claims of 1000 cycles or 1200 cycles or 1600 cycles is as laughable as Jim Gaffigan beating Usain Bolt in the 100 meter dash. In a battery use survey conducted on sailboatowners.com, the largest ever of its kind with 1480 users surveyed, the vast majority of boat owners reported they rarely if ever get more than 150 cycles out of their lead acid batteries. 150 cycles!!!!! Many of these are batteries that have claims of 100 to 1200 cycles or more. Laughable is about the best way to describe it. Lead is dead because the manufacturers dug their own graves by misleading their customers. Perhaps if they had been more honest in setting reasonable cycle-life expectations the mass exodus from lead to LiFePo4 would not be quite as rampant?

The image below is but one example of why I can say lead acid battery cycle-life claims are laughable. I don’t and will never make a claim like this without data. We have been conducting capacity test on lead acid batteries for close to 20 years. While the equipment for capacity testing batteries has gotten significantly better, the quality of the lead acid batteries has not. This poor customer purchased a brand-new bank of Trojan SCS-225’s in the spring. His boat is on a mooring and he did not have solar. I explained to him the batteries may only last 1 to 2 seasons. He was very surprised that based on Trojan’s claim of 600 cycles to 50% depth or discharge. The results below are not atypical. The battery is at 63.4% state of health in just one season. By industry standards a lead acid battery is considered end-of-life when it can only deliver 80% of rated capacity. 20+/- years of testing marine use batteries to BCI Testing standards has taught us that claims of 1000+ cycles from lead acid are about as fairy tale as Tinker Bell..

These days LifePo4 has come down in-price enough to be at near parity with AGM & Gel in a $$ to usable Ah Comparison. When we add in $$$$ to Ah & include cycle-life, LFP is wiping the tears of the lead acid battery makers off the floor..All that said.. Let’s take a loot at current prices;

Lifeline GPL-31XT– AGM- 125Ah X 3 for a 375 AHBank=$1596.96- 187.5 USABLE Ah @50%DoD(at best *300 hundred cycles(real world usage)) =**8.52/Ah
*20+ years of read world experience including many hundreds of capacity tests..

KILOVAULT HLX+ 2400X  2 400Ah BANK= $3090.00 for 320 USABLE Ah @ 80%DOD-5000+/- cycles=$9.65./Ah

KILOVAULT HLX+ 2400  X 2 for a 400AH BANK= $3090.00 for 400 USABLE Ah @ 100%DOD 2000 cycles=$7.73/Ah

A t 100% DoD the cost per Ah is only a little more than AGM

What About Cost per cycle?

HLX2400 Cost per cycle@ 80%DoD=0.62

HLX2400Cost per cycle@ 100% DoD=$1.55

LiFeLineAGM Cost per cycle@ 50% DoD=$5.32.

Drop-In Pluses& MinusesPreface:

This article discusses 12V (nominal) LiFePo4 Drop-in batteries for use on boats.

This is the first article I’ve written since I suffered a major stroke on September 1 (nearly died). It took me six+ months of recovery to get to this point. I am writing this with new speech to text software(Dragon) which is not easy to master and I only have one finger to type with(my left arm/hand are still paralyzed.. My vision was also affected by the stroke so working at the computer for more than about 30-40 minutes a day is exhausting(though with hard work my endurance is slowly getting better). My brain is pretty worn out after 30-40 minutes, so an article like this has taken me more than120 hours to author. I’m getting it done but everything is just taking a lot longer. I am committed to MarineHowTo.com and this article is just the beginning of my recovery. I had started the outline of this article back in August before I had the stroke..

 

What do we recommend for drop in Batteries?

For the highest quality; Lithionics

We also love the KiloVault HLX+ batteries

Good Product assembled in the USA; Battleborn

A Tremendous value are the batteries by *SunfunKits.com

(*use coupon code; marineht for an additional 5% off at sunfunkits.com)

Discuss what you read about in this article in the groups below:

LiFePo4 Drop-In Batteries For Boats

For general Marine electrical systems discussions; Boat Electrical Systems

I Actually Use LiFePo4

It’s important to know that I’ve been using lithium iron phosphate batteries on my own vessel since early 2010 I built my battery bank back in 2009 well before any of these drop-in batteries even existed. My LFP bank will be 13 years old on May 10 of 2022. The bank has in excess of 2200 cycles on it & most every single cycle has been to at least 80% depth of discharge with many many, many cycles (at least 100+ cycles) going to 0%. That battery bank can still deliver 100% of its 400Ah rated capacity so LFP batteries can last, where lead acid don’t.

Having been using LFP since 2010, you could not pay me to go back to lead acid..

Important:This article is not intended to pick on any manufacturer at all. It is intended only to make you a more educated buyer. Where it was possible brand names have been obscured..(I do call out one manufacturer but that is rare for me).

Drop-In LiFePO4 Batteries, don’t you just drop them in?

No you don’t! Any consideration of LFP batteries on a cruising boat must be treated as a system wide approach.Don’t just take my word for it. Boat US is one of the largest insurers in the US.

But, But, they say “drop-in replacement for lead acid?”

“Do Not Connect to analternator”?WOW!I’ve never seen a lead acid battery disallow connection to a non-smart alternator??Drop-in? Apparently not so much?

Terminology Used:

• LiFePO4= Lithium Iron Phosphate also called, LiFe & LFP
• BMS= Battery Management System
• C-Rate- “C “= Capacity and the rate is usually depicted as 1C, .5C.,.33C, .02C etc. A 100Ah battery with a charge rate of .5C would be 50A charge current or 100Ah ÷.5 = 50A
• Load Dump- A BMS Disconnect during charging which disconnects the battery.
  
• VPC- Volts per cell
• Pack voltage- voltage of the entire battery measured at the packs positive & negative terminals

What is a “drop-in battery?

A drop-in lithium iron phosphate battery is a self contained battery that comes in a standard lead acid case size e.g; group 24,27,31 group 4D, group  8D etc..These batteries are self contained and should always have a BMS built in.. Batteries that use an external BMS such as Vicron or some of the Mastervolt or Lithionics batteries are not considered drop-in batteries.

Ignore The Trolls & Safety

Internet trolls pollute the Internet like cigarette butts pollute city sidewalks and gutters. You know who I’m talking about, the undereducated know-it-all who enters any conversation regarding lithium iron phosphate batteries in a Facebook group or boating forum and   starts with; “The only people looking at lithium iron phosphate batteries are the ones who want their boat to blow up”. A great example of this can be found in the “parting shot” of the April /May 2022 issue of Professional Boat Builder Magazine.. Even though the parting shot is editorial in nature,Pro-Boat should be embarrassed by that piece and the complete lack of research on the authors part. Pro-Boat normally works with authors who are actually experts in their field such as Steve D’antonio or Nigel Calder but the author failed to do any research on this topic and put out a grossly under researched apiece..

Let’ cut out the BS right now. LiFePo4 and LiCoO2 (Boeing) are about as different as water and gasoline in terms of resistance to burning/exploding. While LiCoO2 and LifePo4 are both Li-Ion batteries, the chemistries are vastly different in terms of safety. Let’s not forget Flat-Earthers still exist too…

When you see these trolls politely ignore them &, as the internet goes, “don’t feed the trolls“..

Li-Ion= Rechargeable Li
Lithium = non-Rechargeable Li

Don’t just take my word for it here is the FAA

A Reader Challenge

Reader Challenge:I will continue to offer a challenge that I have been offering now for 10+ years on the Internet and that is; the first person to bring me an image of a lithium iron phosphate cell, properly installed, that erupted into flames or resulted in an explosion due to overcharging, I will pay them$50 cash for that image! In 10+ years not one person has been able to bring me such an image…This is because LiFePo4 is an extremely safe chemistry.

A Dramatic example of LiFepo4 Safety

The image below is but one example of the safety of lithium iron phosphate batteries. The cells below came out of a drop in battery where the solar controller failed & the 100V+/- array started feeding hundred+/- volts to the batteries. The BMS tried to protect the batteries but once the BMS shut off. in the solar array was still feeding 100V+/- to the chip in the BMS. Once the chip failed the 100V made it to the FET’s and they too failed allowing the full array voltage to get to the LFP Cells.

No fire, no explosion just swollen ruined cells & cell venting.

The Cells were overcharged so violently that it blew apart the metal case!

HOW IS A DROP IN BATTERY MADE?

A 12 V (nominal) lithium iron phosphate battery is made from four 3.2 V cells wired in series. This is referred to as “4S”. This makes the battery a 12.8 V rated battery. The difference between lead acid and lithium iron phosphate is that each cell in a lead acid battery is a nominal 2 V cell but in a lithium iron phosphate battery each cell is 3.2 V. So, a 12 V lead acid battery requires six 2V cells and an LFP battery only requires four  3.2 V cells.

START WITH THE CELLS & BMS

There are currently three different cell form factors being used in drop-in batteries. the first is called prismatic these are square blocks that nest together and most often require what is called cell compression,the Chinese call this a “fixture” . The “fixture” is used to prevent cell swelling / bulging during charging .

The second type of cell that is commonly used in drop-in batteries is called a cylindrical cell this can be anywhere from the size of a AA battery up to approximately the size of a D battery. Cylindrical cells are quite robust because they don’t need cell compression as the cylindrical form factor prevents swelling. The drawback to cylindrical cell batteries is that they typically require lots of spot welds to connect the cells in parallel cell blocks before they be are put into series series.

the third type of cell for drop-in batteries is called a pouch-cell we typically do not advise pouch cells for use on boats where vibration can be high. pouch cells can be easily ripped and often times they are just dropped into an and aluminum housing that can sometimes have sharp edges. pouch cell drop-ins are getting better and these days have less chance of ripping but prismatic or cylindrical is typically better for use in high vibration environments.

PRISMATIC CELLS & BMS

CYLINDRICAL CELLS & BMS

Pouch Cells

ADD A  BATTERY CASE

Clearly I’ve left out a lot of the important details of the manufacturing of a drop-in battery. In order to build a battery properly the cells must be impeccably matched before the the cell block is assembled. By impeccably matched I am talking about cell to cell Ah capacity and cell to cell internal resistance. If the cells are not carefully matched the BMS inside the battery may never be able to keep up with balancing.We have seen this in numerous instances with drop-in batteries.

What is a BMS?

BMS stands for battery management system. A battery management system is used to protect the individual cells inside the battery. Each 12.8 V (nominal 12 V) drop-in battery must use a battery management system. You could also call a BMS a cell protection system as it actually serves to protect the battery cells inside the drop-in battery. The BMS will protect the battery cells from such things as temperature voltage and current. The BMS also serves to balance the cells should they get out of balance. The BMS protects the battery by disconnecting the battery from the charge sources in the loads. Lead acid batteries do not do this.

Insane Market Growth  of Drop-In Batteries

In the last two years the proliferation of lithium ion phosphate(LFP) drop-in batteries has literally gone berserk. Drop-in technology has finally advanced far enough that I believe it’s now worth discussing in an article. I had previously avoided this topic because many of thethe early drop-in products were pretty poorly engineered, BMS’s had weak power handling etc..

Disclaimer: MarineHowto.com does not currently sell any lithium iron phosphate batteries. Health issues (a near deadly hemorrhagic stroke forced what is perhaps the permanent closure of my local electrical & on-line businesses.We are also not involved in any affiliate programs that could potentially sway our opinions! This site, like always, is for your education only. We want to ensure that you do not get ripped off in the field LFP drop-in batteries. What you get here is an expert opinion that is based on many years of experience in this field(since 2007). With no money potentially swaying these opinions, you’ get an unvarnished view.

While the internet is full of folks claiming to know what they are talking about sometimes it is easiest to just use a photo. The image below shows the ABYC marine safety standards that I work on. I have been involved with the lithium-ion subcommittee since it was first formed back in late 2013. I was personally invited onto this committee by the committee chair.

Beyond being a Marine electrician/engineer, I have been using lithium iron phosphate batteries on my own vessel since Spring 2010. And yes, that  bank (built well before drop-in LFP batteries even existed) is still going strong and it still delivers 100% of its original capacity when capacity tested.

I am also a voracious reader & research junkie;

As can be seen from the image below I have a massive collection of technical documents,research papers&white papers. Everything below is in regards to lithium ion phosphate batteries. I run a 32 inch monitor and I can’t even come close to fitting everything onto one page for a screen grab. This LiFePO4 folder alone has 377 PDF documents on lithium iron phosphate batteries. Yes, I have read them all…

LFP drop-in batteries have come a very, very long way in the last few years but this does not mean there are no sleazy manufacturers left out there. How do you avoid 98% of the poor LFP products? Easy, don’t buy directly from China on your own. If you don’t know what I mean by this I would urge you to spend some time on Will Prowse’s YouTube channel but, please don’t focus on his reviews(in a marine application sense), instead focus on how many failures he’s had cutting open & examining drop-in lithium iron phosphate batteries! Please remember that a manufacturer who is sending Will Prowse a battery often knows darn well who he is.. They still fail to send him well-built / well executed batteries many of them lacking cold-weather protection (You can’t charge LFP below freezing) even though they frequently lie and tell him the battery has it.. If guys like Will Prowse can’t pick quality batteries out of China how can you expect the average Joe to wade through all the murky information and get good LFP drop-in batteries directly from China? Hey, I’m not complaining, Will has indirectly sent us a lot of paying customers! These customers have had a number of issues with batteries,cells or BMS’ he’d reviewed. We’ve made a lot of money testing these batteries in our lab, only to tell the customer they had  been sent “B-grade or reject cells etc… This sort of stuff, has been sold as  “A”grade” but, the customer got “B” grade or reject products. This scammery runs rampant on Aliexpress, Alibababa, eBay, Bangood Amazon etc. etc. so be very careful when ordering direct from China because you’re on your own once you do..!

Purchasing- Rule#1

Rule number one for purchasing  lithium iron phosphate drop-in batteries is that you always want to buy from a well established US or North American company!(This site is read world wide but is still a US based company. (Insert Germany UK, Norway, Sweeden etc. for USA), even if that company is having the batteries manufactured in China. Hint: All lithium iron phosphate cells are manufactured in China. Some US manufacturers such as Battleborn choose to import the components from China and assemble them here in the US. This allows them to better control assembly quality. You want, and need a presence here on North American soil (insert your country here)  to ensure that the company can stand behind the product and you are protected by US (your country) consumer laws..

Most of the “bad” images you will see below are what happens when aDIY attempts to become the importer of LFP batteries.These sorts of issues are almost non-existent  where a decent US company is behind the importation design & manufacturer selection process.

Disreputable sellers will lie and think nothing of it. This LFP cell is 100% made in China……

Always Check with your Insurer First!

The image below is from Markel, one of the largest insurers of boats in the USA.

And here’s an insurance questionnaire/form. Lie on this document and guess what ? You’re not covered!

Important:This insurer wants to see a US company, on US soil so they  have someone to go after should an accident occur. This is why they demand a company based in the US.

Batteries such as Kilovault (MA), Lithionics (FL, Battleborn (NV), Dakota (ND), Relion (SC), Mastervolt (WI), Victron (ME), Trojan (CA), Lifeline (CA) etc. would meet this criteria.

Batteries that come directly from China such as SOK, AmpereTime, Chins, AO Lithium etc. Would not meet this criteria.

There are still many insurers who allow LFP but please check with them first!

What About the ABYC:

If your Drop-in battery cannot meet the underlined criteria (Insert “Strong-Opinion”) you  may want to keep looking:

ABYC TE-13

What About the ISO/ European Safety Standards:

ISO/TS 23625
ISO is Pretty Similar to the ABYC only this standard is active now (ABYC E-13 coming very soon)…

“Rod, isn’t the ABYC is a “voluntary” standard?

Absolutely, but here’s the rub. Every Marina in the United States, and most in Canada, require insurance. If you’re vessel is insured the insurance company has standards they expect. In North America those standards are the ABYC standards. They use Marine surveyors to ensure the boat is safe and up to their underwriting standards. Marine surveyors are currently using ABYC TE-13  as a guide for LFP installations and are actively calling out installations that don’t meet the nature of the TE-13 document.We get emails about this routinely.Our answer is, as always, do as your insurer requests as finding another policy especially if your boat is older can prove to be very difficult..

ABYC TE-13 is currently a technical edition (TE)meaning a technical white-paper defining safe installations. TE-13 will be converting to a full-blown standard called E-13 perhaps as soon as July 2022(could be earlier too). I cannot speak to any of the specifics at this point because I am under an NDA (non-disclosure agreement). Throughout this article I will give some “strong opinions“on what is safe and what is not. You can take from those opinions what you what you want. My opinions will be based on what the final document may look like.

Be Very Careful With the Marketing!

“Marine Grade”

I’m not intending to pick on this manufacturer but it is a good example of where marketing and standards can clash..  Recently a customer emailed us about the new XXX Brand “Marine” batteries, a brand we had never worked with. He is insured by Markel. A couple of days later he sent us this email:

One would think a battery marketed heavily as “Marine Grade” would actually meet the Marine standards?

  YouTube Reviews

I really do like like Will Prowse and I think he’s doing the general public a tremendous service in cutting open all these drop-in batteries and exposing all the dirty little secrets. We too have cut open a slew of these batteries I just don’t do video or video editing well..  The problem I have with Will is that he does not operate in the marine environment and the marine environment is a different set of circumstances & standards than it is for RV or off-grid cabins. For example, I don’t know a single RV that has a 12V bow thruster that can pull over 600A(no load rating) at 12 V and 1600A+for in-rush LRA/FLA rating. An in-rush like this is capable of ruining some FET BMS boards especially after repeated thrusts.

We have had too high a number of readers & a few customers(who self installed) destroy or damage drop-in batteries with their bow thrusters and windlass motors! The good news is that FET BMS’s are getting bigger and more robust all the time so these issues (wimpy FET BMS’s) may soon be behind us…As you can imagine, it gets very, very expensive when you ruin a battery by applying too much in-rush current.. Be careful taking Wills advice at face value for a Marine application is all I’m saying.

Having been asked over and over what “Drop-In” batteries Compass Marine Inc. prefers, likes or That we believe are well designed, the following two brands are where we stand today.

Lithioncs $$$$$$$-Amazing quality drop-in batteries. Built like no other LiFePo4 batteries!

KiloVault $$– These 100Ah, 150Ah and 300Ah 12V batteries are very, very well built for the price point and include one of the most robust BMS’s of any drop-in product we know of. They also use extremely high quality aluminum prismatic cells and each battery has Bluetooth built in for external communication & “visual” TE-13 compliance. Even the busbars inside these batteries are made of Nickel plated copper. Having torn piles of LiFePO4 batteries apart I can say without a doubt these represent one of the best values there is in a 12V drop-in battery.

Is Your Vessel a Good Match for Drop-In Batteries?

Use this flow chart to find out

An upgrade to lithium iron phosphate batteries can always be done in stages. We typically advise starting with the charging system first, as your on-board items become antiquated or become failure prone. We suggest upgrading any sort of charge equipment eg; solar controllers, alternators or alternator regulators with devices that can be fully programmed for lithium iron phosphate batteries in the future.Doing this as the items begin to become failure-prone means that in the future when you’re ready to upgrade to lithium iron phosphate batteries your system will be ready for it.

Let’s Look at Drop-In Battery Specifics:

The popularity of drop-in LFP has literally exploded in the last 2 years. This is good for LFP batteries as a whole, but can also potentially be bad, if the right drop-in’s are not chosen to properly match your vessel.. There are things that need to be considered beyond just “dropping them in“. The term “drop-in replacement” is a very misleading moniker, as these batteries are far from a “drop-in” replacement for lead acid.

Drop-In batteries are most often sold in standard lead acid case sizes eg: Group 27, 31, 4D, 8D etc.. One of the drawbacks to a drop-in battery is that most of them lack any external communication between the internal sealed BMS and the vessel. Currently the 320Ah Lithionics GTX12V320A is the only drop-in marketed battery that offers external communication between charge sources and the battery.

Most of the drop-in batteries have been Chinese in origin, and this is not necessarily a bad thing, if you’re buying from a reputable manufacturer. A large number of the US available brands eg; Trojan, Lifeline, Relion, Kilovault etc. are buying from a hand-full of premium Chinese factories. The difference between straight up US sticker applicators & Trojan, Lifeline Relion, Kilovault and pure US based sticker applicators is that Trojan, Lifeline Relion  & Kilovault designed the batteries and have them built to their specs just like Apple computer does.

Where drop-in LFP batteries often fail the purchaser is in marine specific engineering. To understand why, we simply need to look at the reason these batteries were originally created. Drop-in form factor LFP batteries were originally designed for telephone pole mounting where light weight and “drop-in” replacements for lead acid were critically necessary for the solar powered street lighting & cell repeater industry. The demand for this type of battery, especially in third world countries, is absolutely staggering.

Drop-in batteries were not invented for the use  you think they were

I know many boat owners tend to assume we are a large market, but we are not, and no, many of these drop-in manufacturers are not specifically building marine batteries for us, though they certainly are marketing to us. The application of a “marine” sticker, and perhaps even a well marketed brand name on the plastic box, does not always denote a product that is well engineered or specifically engineered for use on a cruising boat.

Unfortunately, for our industry, many of the “A” graded LFP cells used in the plethora of Chinese drop-ins, are sold into the street lighting or EV market industries. Please understand that the term”A” grade is really a meaningless-term in China. “A”grade really means EV grade but the Chinese have figured out that people think “A”grade actually means something…It may actually mean “A”bhorrent grade” depending on who you buy from

For boaters buying drop-in batteries direct from China this can mean the low-grade “orphaned” or “rejected” cells wind up in batteries that may look exactly the same but are sold on Ali-xxxx, , eBay or through other less reputable sources.. Once the cells are sealed in its glued together plastic case you the buyer have no way to know what quality cells you got.Below is an example;

Direct from China FAIL! This battery came directly from Aliexpress:

You may ask yourself why I say take Will Prowse reviews with a grain of salt? This image explains exactly why I say that. I have yet to see Will’s reviews include a discharge capacity test of each individual cell in the battery. I know darn well why he does not do this …. Time.. We use the exact same computerized capacity tester Will does, plus a few others, but this stuff takes time, lots of time. The problem with this Aliexpress battery is that the cells had a 8.3% variance in their Ah capacity! This battery tested at 100% capacity on cycle #1. On the recharge is where the problems showed up. As a result there was no way this particular BMS could ever keep the cells in balance. The bottom line is this battery was built from reject /grade B cells that never should have been in a battery that was marked or sold as “A” grade! We’ve done lots of testing for viewers of Will’s that confirmed the cells or battery they got from Aliexpress were not actually A grade or EV grade cells.There are not many companies capable of doing this testing, so this has meant quite an in-flux for us in the last few years.

Sadly Ali-xxxxx has literally become the numero-uno dumping ground for reject LFP cells and batteries from the Chinese factories. They get away with this because they know the vast majority of buyers have no way properly to test them once the battery case is glued together. Frustrating? You bet it is! Always buy your LFP batteries from reputable companies not directly from China unless you love to gamble.

The internal BMS in this battery was completely incapable of balancing the cells & one high cell kept tripping the BMS on high voltage. 3.65V is the maximum safe cell voltage for a LiFePo4 cell (the image above has two cells in the danger zone). We spent about two hours reprogramming the BMS after multiple emails back & forth with the manufacturer who refused to give us the BMS passcode so we could custom program it to make it work better for poorly matched cells. We then tried to charge it and to get the cells balanced for three straight days. Nothing we did could balance the cells so this battery would not trip the BMS on cell high-voltage.Please note the recommended charge voltage was 14.6V and even at 14.2V we have two cells well into the danger zone.

The customer finally gave us the okay, after emailing with the manufacturer,  to open the battery and test each cell individually. This required the complete destruction of the battery case because it had been glued together with what appeared to be superglue. The only way to get open was to cut it open. When we finally capacity tested the cells it was discovered that there was an 8.3% variance in cell to cell  Ah capacity on these four 100 ah cells.There was no way this BMS was going to keep up with that variance, balancing wise.

Once the manufacturer had the testing data they then backpedaled on the warranty and refused to take battery back because the battery had been cut-open(which they had said was ok). The customer was out all the money he spent on shipping plus the battery costs direct from China(His take was that as an Aliexpress buyer you have no rights and no recourse). He was also-out  about $380 in labor for our shops testing costs. In the end he wound up buying two KiloVault batteries and has had zero issues since..

Drop-In LiFePo4 – Important Points to Consider:

 BMS Current Handling 

The current rating of the internal switch that protects the battery is quite often too small for the task on many cruising boats. Drop-in LFP batteries routinely use multiple tiny little MOSFET switches as the batteries BMS protection ON/OFF switching. Unfortunately these FET’s often can’t handle the typical loads imparted by many cruising boats. On board devices such as bow thrusters (400A +), windlass’ (100A to 300A+, large inverters 150A to 300A +, electric winches 75A to 300A +, electric cook tops, massive alternators, chargers or large inverter-chargers are very very common on-board cruising boats these days. These are exactly the devices many boat owners are hoping to see a gain in performance from when switching to LiFePO4.

This is what a 120A rated FET based BMS looks like it is pretty for a typical 100Ah drop in battery. This is what an internal FET based BMS boards typically looks like with the heat sinks removed. The blue wires connect to the neg end of the cell string and the black wires are connected to the external negative battery post.fet bms’S DISCONNECT ON THE NEG SIDE OF THE BATTERY This one uses two 10GA wires for its 120A continuous rating. All 120A has to pass through those two 10AWG wires, the printed circuit board and the FET’s. The hotter FET’s run the shorter the MTBF (mean time between failure) is. This Particular BMS ,a JiaBaida, uses 32 FETS(the board has double sided FET’s.  We have cut open drop-in batteries with 100A rated BMS’s ( that use only 10 FET’s.(see image below this one)..

What a FET BMS Looks Like

The Miniscule BMS below came out of a customers AliExpress  drop-in that was sold as a 100A continuous BMS. It was also sold as Hot and cold temp protection. As can be seen the temp sense port(only one port not two.) is not even soldered to the BMS’s PCB. Hard to have hot and cold BMS protection when the sensor ports are not even installed. These are the “Lies” we talk about when flying solo and ordering directly from China..Oh and this was wired to the batteries neg terminal with 12AWG wire…! 12AWG/100A!

Do You know the quality of the FET’s ?

What if I have High-Current DC Devices?

If you own a vessel with high load devices, do yourself a favor and look at the contactor ratings (the BMS protection switch) that “marine specific” companies such as Lithionics/OPE-Li3, & Mastervolt use for their”marine specific” LFP batteries. What you’ll often see is a 500A continuous rated Gigavac, Blue Sea ML-RBS, Tyco EV-200, or in the case of Lithionics, military grade 500A contactor/relays are being used as BMS protection switches.

Compare that to some of the drop-in batteries being sold out there which can have relatively low-current handling capability due to the use of often under-designed( for a cruising boat)FET based switches. The manufacturers building “marine specific” batteries eg; LFP Mastervolt OPE-Li3, &Victron know what a typical cruising boat needs in terms of current handling and they engineer this into the product. Does this mean you need to use a “marine specific battery? No, it does not it just means you need to choose your drop-ins very carefully for your vessel.…

A Dead FET BMS (windlass in-rush)

Below is the BMS “switch” used by Mastervolt on their MLI series LiFePO4 batteries. It can handle bow thrusters, large windlass motors, massive inverter-chargers, massive alternators. etc.. The ML-RBS  switch is rated for 500A continuous, 700A for 5 full minutes and 1450A for as long as 30 seconds. While many smaller boats can often get by with a FET based BMS, not all boats will, so please consider the max continuous discharge and recommended charge ratings of the battery you are purchasing. This rating is not usually limited by the cells but rather the internal BMS’s current handling capabilities.

Let’s take a look at the BMS switch Mastervolt  uses. (Lithionics uses a similar switch on their external BMS batteries.

You read that correctly; 500A continuous or 1450A for as long as 30 seconds!!!

Sadly, when buying direct from China,you can still find diminutive 50A continuous rated FET switching BMS’s installed inside a 300Ah LFP battery. As a comparison a 150Ah KiloVault can handle 150A continuously or 200A for as long as 30 minutes. While a 50A rated BMS may be fine for small boats,  if you have large on-board DC loads, or want to charge a 300Ah battery quickly, then a battery like this is going to be a less than ideal battery for marine use. So, you still really need to do your homework to make sure the batteries & the internal BMS are a fit for your vessel.

Building a Drop-In Bank to handle Large DC Loads

When it comes to FET based BMS batteries we typically advise smaller individual batteries, wired  in parallel. This is done to share the load across the FET based BMS’s. For example three 100Ah / 1C rated LFP drop-ins can theoretically handle a 300A discharge, if the parallel wiring is perfect and all batteries share the load equally(rarely happens that way.) A 300Ah 8D format drop-in, like the one addressed below, can really only handle a 100A (0.33C) discharge. When in doubt with FET based BMS systems smaller batteries in parallel are usually a better solution than one large battery with a low current rated BMS.

You Need to Read The Specs Carefully!

Purchase FAIL!

Sometimes one just has to laugh when reading the specification sheets on some of these direct from China drop-in batteries.

This drop-in LiFePO4 (LFP) battery is rated at 12V-300Ah with a maximum charge current of just 50A!

A 50A max charge current on a 300Ah battery is a charge rate of 0.16C

0.16C IS A LOWER CHARGE RATE THAN A FLOODED LEAD ACID BATTERY CAN HANDLE

The specification also claims 2000 100% SOC to 0% SOC cycles, not too dis-believable for LFP. However they then claim 20,000 cycles at the end of the spec! This is at least double what any reputable LFP maker claims! It then claims “fully charged in 60 minutes“.

“Fully charged in 60 minutes” Holy $hite, that’s fast, but just to be safe, lets do the math..

300Ah battery at 0% SOC – 300Ah / 50A = 6 hours –Fail

300Ah battery at 20% SOC – 240Ah / 50A = 4.8 hours –Fail

300 Ah Battery at 83.4 SOC – 50Ah / 50A = 1 hour –Winner

You read that math correctly. The only way we you can get this battery to charge in 60 minutes is if you only discharge to 83.4% SOC……. So much for those deep-cycling &  “fast charging” LiFePo4 batteries? My point here is to help you learn to dig deeper into the specs so you can learn to spot bogus claims.

If you’re less than educated on a subject, drop-in battery makers will try to sell you anything you want to believe. Educate yourself and do the research

Another Purchase FAIL!

The image below is a prime example of how boat owners, without enough knowledge, can get burned buying LiFePO4 batteries. We were consulted by an owner who purchased a 300A drop-in battery from what he thought was a “reputable manufacturer“. During the transaction, he had no consultation with the manufacturer and no questions were asked by the re-seller. He just ordered it based on it’s “8D drop-in” format, the claim that it was an exact drop-in replacement for his lead acid Lifeline 8D battery, and the 300Ah capacity rating.

He felt comfortable because it was, what he considered, a “reputable manufacturer” and they are based here in the USA. He quickly destroyed three alternators and the BMS kept disconnecting when he was inverting with his large 3kW inverter/charger. The BMS disconnecting while charging also damaged his inverter/charger. When I pulled up the spec sheet on the 300Ah drop-in battery he’d purchased, the problem became crystal clear. It is highlighted in yellow below….

You are reading that correctly, this massive 8D form factor LiFePO4 battery was only capable of a 100A discharge and a max short duration charge of 100A. To keep the BMS cool, and the cells balanced, the manufacturer has a “recommended” charge rate of just 15A to 50A for a 300Ah battery. This 15-50Ais not a limitation of the cells inside the battery it is a limitation due to the FET based BMS that is used to protect this battery.

PURCHASE FAIL! For this particular application this drop-in was a horrible fit. A fault of the battery? No, not at all. This was a shared failure in the marketing, the retail chain, and of the owner. I partly blame the owner here because he failed to do the research and fully comprehend the specifications of what he was actually buying. Of course who can blame him when these batteries are boisterously marked as “drop-in replacements“. As can be seen from this example these are ABSOLUTELY NOT drop-in replacements for a lead acid 8D battery as his Lifeline 8D’s never once disconnected themselves from the alternator or the inverter…

What EVERY Drop-In Battery Spec sheet SHOULD Look Like

*Highlighted specifications are the critically important ones.

High Voltage Disconnect (HVD) Cut-Off Protection: This is critical to know because it is the voltage at which the BMS will disconnect the battery from the vessel.This is usually specified on a per cell basis. So a 3.65V disconnect on a 12V battery would be 3.65V X 4 cells=  14.6V BMS Disconnect Minimum Absorption Voltage (to Initiate Cell Balancing): This is important because you need/want to activate balancing with each charge cycle. You also want to avoid pushing to the maximum charge voltage every cycle if you wish to maximize cycle life. Maximum Absorption Time: Again, This one is critical to cell longevity. If it suggests a maximum absorpyion duration of 30 minutes you had better make sure all your chargers can be programmed not to exceed this.. High Internal BMS Temperature Charge Cut-Off- This is one you have little control over other than to not push your BMS near the charge-current limits. It is always best to charge at no more than the “recomended charge-current. 95% of the load-dump damage we’ve seen is not due to high voltage cut-offs but rather from a BMS disconnecting due to BMS Temp. Be Sure your manufacturer specifies This!

High Internal BMS Temperature Discharge Cut-Off:  same as above but for discharging. Delay until Peak Discharge Overcurrent Protection Cut-Off: This spec, from a reputable manufacturer ,will almost always be followed by the millisecond rating (ms)before disconnect eg:320A 8ms This would mean the BMS will disconnect if it sees 320A for 0.008 seconds or more. This is why knowing the in-rush draw of all DC Motors is critical before installing LiFePo4 drop-ins. Recommended Continuous Charge Current: Always follow this guidance not the “max charge current.The reason for this lower number is to keep BMS temp down and to allow balancing to keep up. Many of these BMs’s only have 20-390mA of balance current to work with! If the celllsget out of balance & you are fast charging the BMS may never be able to keep up!! Maximum Parallel Configuration : (Identical Model Batteries): Do not exceed this number! Maximum Series Configuration:(Identical Model Batteries):Do not exceed this number!

If you are unfamiliar with what the specifications mean or why they are critical you may want to reconsider drop-in batteries until you have completed the research phase.

Vibration

Many of the very cheaply sourced drop-ins are using 18650, 26650 or 32650 cylindrical cells inside the battery case. In a worst case, a 100Ah LFP battery, built from 18650 cells, would need a grand total of 364 cells with two connections per cell.

Hows that math work?

18650 Cell = 1.1Ah (typical Ah rating for an 18650 LFP cell)

91 Cells Make Up Each 3.2V cell

Four 3.2V Cells Make Up a 12.8V 100Ah Battery

91 X 4 = 364  18650 Cells

Positive & Negative Connections Inside The Battery = 728

If the manufacturer uses 5Ah 32650 cells, and some do, we then only need 80 cells total, and 160 spot welds or bolted connections to potentially fail or work loose. (32650 cells are available in bolted or spot weld versions)

The connections, with 18650s’s, are almost always spot welded to end boards that make up the individual cells.  So, in a single 100Ah battery, made of 18650’s, just to connect the cells, we have as many as 768 spot welds to rely on. Beyond that we have all the internal wiring and BMS connections. These spot welded assemblies are often just dropped into the polypropylene case with no other support or vibration dampening material.  To be safe, always be sure to ask the battery supplier to furnish third party vibration testing results or testing to UL or IEC vibration standards.

A Look at the BAD of LFP:(most of these images are “direct fromChina” purchases).

Do you suppose this Rube Goldberg level Ali-xxxx LiFePO4 drop-in battery manufacturer, and I use the term "manufacturer" sarcastically here, has paid to have this battery vibration tested?
                                 Image courtesy MHT Reader

No  Not Kidding!

                                                     Image courtesy MHT Reader

Heck the guy assembling these cells, most likely in his mom’s spare bedroom, can’t even solder well or use a spot welder with any level of quality or precision. Vibration testing? Only if they are flat out lying about it. Purchasing LFP anything on Ali-xxxx is a very strong buyer beware!

This LFP”starting battery” has NO BMS Protection!! Balancing only!!

                                                                     Image courtesy MHT Reader

Starting a 44HP Westerkeke takes…….640A!!!!

What’s Wrong here?

OK, I’ll Help Out.. Look closely at the series connection below!!!!

An 18650 cylindrical-cell battery failure

How did we discover the spot weld failures? The zipper like discharge graph was a dead giveaway..After a discussion with the manufacturer we had to tell the customer to stop using his bank immediately…It had also lost significant capacity from over charging.His lead-acid charger that held 14.6V way too long. We were testing them for capacity when we discovered the spot weld failures (brand purposely obscured). In the screen grabs below you can see how varied the voltage was on discharge.We had wanted to run the discharge at 40A but the zippered graph was even  worse at 40A so we ran the capacity test at 10A..

Data point =12.582V

Data point = 12.702V

What happens when you cram multiple small wires into one terminal and ask them to carry 100A +/-Hint: You get terminal melt down..

And here’s what they look like when you hit them with thermal imaging.

This is the level of “quality” you may find inside that beautiful plastic case

Because you can always trust the sticker on the outside of the battery

More Direct from China misleading BS

 

A FET  BMS has aluminum heat sinks because it needs cooling. Stuffing it in-between foam blocks is well…… not a wise solution.

But, some dude on the Internet said LiFePO4 is 100% safe…..

No battery chemistry is 100% safe, especially when you over charge it.(However no-fire , no-flames & no explosion just cell swelling and heating… FWIW this “starting battery” has zero BMS Protection!!

                                                                        Image courtesy MHT Reader

Do you know what horrors are hiding in that”direct from China” plastic box?

The Battery Below(image5) is typical of the Quality you’ll often find on Amazon or Aliexpress. So, what happened?

1-BMS is Catastrophic protection only. If a BMS allows cells to charge beyond 14.6/3.65VPCWalk away!!

2- BMS Allowed cells to hit 15.6V /3.9VPCbefore disconnecting!max safe cell voltage is 14.6V//3.65VPC

3- Cells were not in a case that provides cell compression to limit cell swelling

4-Cells balooned and split the battery case open- Battery ruined.

Aluminum Prismatic Cell ruined by over-charging

*image5– Cells ballooned/swelled  due to over charging. This BMS was catastrophic protection only and allows the cells to hit 15.6V before the BMS disconnects (this is enough to ruin the cells and totally brick the battery)

This what proper cell compression for prismatic cells looks like looks like! Has your chosen manufacturer included this?

The “Bad”images above are a reality of what you can often find buying your batteries directly from China without a reputable company insulating you from these horrors…

One last warning about buying direct from China

What Better Quality Looks Like

Compare the above cell block from Ali-xxxx to the photo below of a Lithionics g-31 drop-in battery. This battery uses impeccably matched aluminum encased 5c LiFePO4 cells. The cells are fixed in place by an injection molded jig that protects them from movement and vibration failures. The busbars are high grade nickel plated copper and self locking flange/wizz nuts are used to hold the cells to the busbars. The BMS used in this battery is certainly FET based but it is made here in the USA, of Mil-Spec components, and is designed to handle starting engines. There is a huge variance in the quality of LiFePO4 drop-in batteries. Yes, this battery is more expensive than a 100% Chinese made drop-in, and they are only sold after a consult to ensure they are the correct fit for the vessel. Bare minimum alternatives to the Lithionics would be the KiloVault HLX Series. A lot of folks swear by Battleborn but the Battleborn batteries to not yet meet ABYC requirements for E-13.E-13 will be official in about 60 days from this article being published.

Internal Wiring 

It is not uncommon to open a 100Ah drop-in battery, rated at 1C, and find a single 10GA or 12GA wire feeding the main positive and negative terminals. When someone finds a 10GA or 12GA wire rated for 100A, under any safety standard, please let me know?

This is how Lithionics does it on their 4D 320Ah drop-in.

BMS Shortcomings -Lack of low or high-temp Protection

Some of the drop-in batteries may lack  BMS temp protection altogether . Drop-in batteries should have both low and high temperature protection (a requirement for both ABYC and ISO) but many don’t. Far too many drop-in batteries lack low temp protection and a large number of manufacturers who claim it has low temp protection are actually lying about it. If  You live up North,buyer beware!

Non-Communicable BMS 

This one is perhaps the most frustrating aspect on-board a cruising boat. For a trolling motor, who cares? It’s not powering anything critical. For a house battery, on a cruising boat that ventures off-shore, and is powering critical navigation and safety equipment, this can create a dangerous situation. A non-communicable BMS is one that can not communicate externally with the vessels charge and load systems, or even you the owner. It has no means of externally communicating or sending/sounding warning alarms or activating relays/triggers to properly and safely disconnect charge sources or give ample warning of an impending BMS disconnect. Some batteries are now featuring Bluetooth monitoring but this still requires you the owner to be watching it.

Let’s take a look at one of the worlds most respected marine standards for shipping etc., Bureau Veritas.

As can be seen, under Bureau Veritas standards external communication between the battery and the rest of the systems such as charging is a requirement. For why see below.

WHAT ABOUT CHARGING?

LFP batteries are charged using a CC/CV profile. This means constant-current/constant-voltage

Bulk = Constant-Current(charge source working flat out  or as hard as it can)
• Absorption = Constant voltage( voltage is held steady for a short time or until current declines to the manufacturers spec.
• Absorption Duration = Once the batteries have achieved the absorption voltage the time the batteries spend  at this voltage must be limited. Many lead acid charge sources spend far too long in absorption and this is not healthy for LFP

BMS LOAD DUMPS

DON’T FORGET YOUR ALTERNATOR

Email from MHT Reader:

“RC,

The alternator for the Volvo MD2030 with 300 Amps LiFePo4 14.6 max lasted a few hours. I believe BMS was switching on to off  I to keep theLiFePo4 voltage to safe measure? Boat service replace alternator and it happens the second time? I now read your story on lfp and it explain to me why.”

Unfortunately the reader above learned the hard way. Ask yourself what happens when your alternator is in bulk charge, supplying all the current it can, and the internal BMS decides to “open circuit” or disconnect the battery from the boat? I’ll help out a bit here.

BMS load dump illustration
What a voltage transient looks like:

The load dump transient captured in the above image is from an ISO test of a 12 V automotive alternator. Of important note is how quickly this transient surpasses 90V. The transient surpasses 90V in just 0.01 seconds!

   A) The alternator diodes, unless avalanche style, (rare in many existing marine alternators) but all Balmar alternators now use them, can be blown and the alternator can be rendered non-operable. Two years ago we  did exactly this. Using the alternator test bench here at CMI the 90A  alternator was running at full bore charging an LFP battery. The “system” I set up had a .3A dummy load on, light bulb, to simulate a depth sounder. With the alternator running at full bore I disconnected the battery, just as an internal sealed BMS can do for BMS temp, cell diff-voltage or cell high voltage. Poof went the alternator diodes and the light bulb was burned out instantaneously! Worse yet the voltage transient I recorded on the “load bus” (think your navigation electronics) using a Fluke 289 was 87.2V. Ouch. Even if your alternator uses avalanche diodes, like Balmar’s do, the voltage at which they begin to protect the alternator is far too high for the vessels load bus equipment so you still need a way to protect against a load dump.

   B) If the boat is wired, as is typical with drop in batteries, the voltage transient caused by the open circuited alternator will now directly feed the DC mains and potentially destroy your navigation equipment.

TIP: At a bare minimum, every drop-in LFP battery bank, that can be charged via an alternator, should be installed with an Alternator Protection Module!

The Balmar Alternator Protection Module is an inexpensive insurance policy against a BMS load dump destroying your alternator. If you can afford to purchase drop-in LFP batteries you can also afford to protect your alternator from a BMS load dump.

A well designed marine specific BMS would open a relay that can de-power your charging sources on the input side, thus shutting the charge sources down correctly and safely with no risk of a damaging voltage transient. For a large inverter/charger it would de-power the AC input side, for an alternator it would de-power the field wire or regulator B+, for solar it would open a relay in the PV feed etc. etc.. With a drop-in battery, that features a sealed BMS, you have no way to do any of this. Only Lithionics Drop-In Batteries have this Capability.

But Rod, I plan to program all my sources below the BMS disconnect voltage.

Sounds like a good plan right? Well, lets examine the reasons a BMS can disconnect

This image sums up why programming a lower charge voltage cannot always protect against a BMS disconnect.

Are  BMS Load Dumps Real?

I’ll  let Balmar Explain this;

How about a fairly knowledgeable owner who bought a very beefy alternator and still killed it due to BMS load dumps.

Drop in batteries with the exception of Lithionics do not have a way to properly shut down the alternator before the battery disconnects. For this reason we need work arounds..

The number one reason we see batteries shut down(when everything is programmed correctly) is almost always due to BMS temp related issues not necessarily  high cell voltage..

A good technique to mitigate load dumps is to keep a buffer “load” on the charge bus at all times (Buffer load = lead acid battery on the systems charge bus see FET Isolator wiring below). With FET isolators we like to see them at least double the rating of the alternator eg; a 200A ARGOFET for a 100A alternator. The cooler FETs run the longer they last.   And yes, we have seen FET isolators fail…

Load Dump Work-Around’s

Using Low Volt-drop FET Isolators

Using Low Volt drop FET Isolators

USING DC to DC CHARGERS

There are many benefits to using DC to DC chargers. One of those benefits is that the charge profiles can be custom configured to charge lithium iron phosphate batteries where your factory alternator or legacy lead-acid charge equipment cannot be programmed for this. The Victron and Sterling power DC to DC chargers can also absorb a load-dump from a BMS disconnect where your factory alternator cannot.

However, caution needs to be used when sizing DC to DC chargers. A DC to DC charger should be sized at a maximum of 50% of the factory alternators rated output. This means if you have 100 amp factory alternator the maximum DC to DC charger you should use is 50A. This will help keep the alternator cool and keep it from burning itself up. Currently there are only two DC to DC chargers we recommend and those are Sterling Power and Victron.

The only drawback to using DC to DC chargers is that you give up charging your lithium ion phosphate batteries quickly. Seeing as that is one of the major benefits of  LFP batteries we would strongly advise considering an externally regulated alternator with an external regulator  such as the BamaMC-618 or Wakespeed WS-500these regulators can be programmed for LFP and have an alternator temperature sensor to protect the alternator from heat damage. This will also result in considerably faster charging!

Caution:I don’t often do this as I hate to ever advise against any manufacturer but there is one manufacturer that we would urge a very strong caution on and that is Renogy. We’ve not seen a manufacturer with this many failure prone products in 30+ years in this market. Their failure rate is far too high for us to even consider making a recommendation. Consider yourself warned about buying Renogy.

You can read about  DC to DC Chargers HERE.

WARNING:Do not size a DC to Dc charger at any more than 50% of your stock alternators rated output!

The drawback to using DC to DC chargers is that it results in SLOW LFP charging

Using a Victron Orion TR Smart DC TO DC Charger (Be sure it is not the Orion TR- it must be the TR SMART)

CAN I USE MY STOCK ALTERNATOR?

The short answer is we do not advise this for charging lithium iron phosphate batteries directly.You can however use your stock alternator if i it is behind a DC to DC charger that serves to protect it and that provides the proper charge profile for the lithium iron phosphate batteries.

WHY?

1-A stock alternator rarely has the correct charging voltages for lithium iron phosphate batteries.
2-They can over absorb the batteries resulting in over-charge damage
3-The absorption voltage is very often too high (see below)which  can lead to BMS load-dumps
4-Stock alternators do not FLOAT, they only do bulk and absorption.
5-Alternator heat damage

Do You know the voltage set point of your stock alternator?

Please understand that we have been an alternator manufacturer for more than 15 years so we understand internal vs. external regulators and how these alternators are built. We also have access to data, such as you’ll see below.This is data the average DIY would never have access to.

The max charge voltage for any drop in LFP battery is 14.6V(some are much lower). Below is a sampling of common internal voltage regulators. Pay attention the voltage set points!

 IF your BMS Disconnects at 14.6V / 3.65VPC a reg with a 14.6V set-point is likely to cause you BMS disconnect issues.

These are the most common regulators found in the very popular Delco 10/12Si series Alternators

There is also the Potential for Alternator heat damage!

LFP batteries have a tendency to enjoy eating alternators for lunch. The internal resistance of LFP batteries is extremely low resulting  in very long bulk-charging times. As a result alternators can burn themselves up trying to charge these batteries. I’ve said this many times before on the site and I will say it once again, there is no such thing as a small frame alternator that is continuous duty, I don’t care who built it!  Because Compass Marine inc. is a manufacturer of marine alternators so we get to see these failures regularly. We are not an n=1 data point like the “dude on the internet” who says your stock alt will be fine charging LFP. We have seen far too many alternators completely melted down by LFP batteries to ignore this information..

If you insist on using your stock alternator we would strongly recommend that you put it behind a DC to DC charger (50% smaller than your alternator amperage rating. This will help limit the amount of work the alternator is doing and protect it from a meltdown.Doing this means you can continue to use your stock alternator.

If you expect to charge lithium iron phosphate directly from the stock alternator without a DC to DC Charger in-between, we advise not changing a thing. Do not increase the wire size  to the battery bank ,do not move the volt sense a wire do not touch the factory wiring .zDoing so can result in an alternator meltdown. The typicalfactory wiring on these alternators is horrible and results in a lot of voltage drop. That in and of itself can help protect your alternator from melting down.

Why does LFP cause heat damage?

It is very simple your alternator never catches a break!

Our assembly bench on a typical day..

Don’t be this guy!

ImageCourtesy MHT reader

This stock Yanmar/Hitachi alternator was destroyed in a matter of weeks with just three 100 amp hour drop-in batteries.

Another burned up stator from charging LFP

Oh crap another one!

Jesus H…..! Another LFP Cooked alternator

But Ample built good alternators? Yes, they did but during this vintage Ample Power did not believe in using an alt temp sensor on their regulators.. When LifePO4 came around…Toast!

Series Wired Systems ?

In a parallel wired bank one battery BMS dropping out only creates problems when it re-engages into a different SOC than the rest of the bank by causing a large in-rush. With a series bank (for 24 V 36v or 48V a single BMS taking itself off-line spells disaster at sea and takes out the entire bank. I know a Drop-in owner who hit a granite bridge abutment in his electric boat using a 48V series bank of drop-in batteries. It did a few thousand in damage to the boat, and his pride, but it could have been much worse. The owner had zero warning the battery was about to disconnect itself before he lost all propulsion power. This failure occurred going under a drawbridge in a very strong tidal current. This is but one reason why the ABYC & ISO European standards make sense. Kilovault will soon be out with a communication system for series wired batteries so they stay in balance.We do not advise series wired drop-in batteries unless the BMS’s can communicate with one another. Parallel batteries stand a much better chance of remaining in-balance, series batteries do not unless the BMS boards can communicate with one another.

CATASTROPHIC PROTECTION BMS VS. CELL HEALTH PROTECTION BMS

Please don’t assume every drop-in battery BMS will manage your battery for maximizing cycle life, it may not do that! The BMS in far too many drop-in batteries is designed for catastrophic level protection only. Catastrophic protection means the BMS is only there to protect the cells from thermal run-away conditions. They can have BMS disconnect voltages exceeding 15V for a 12V nominal battery. The max safe cell voltage for an LFP cell is 3.65V X4 cells = 14.6V max. It is up to you, the owner, to ensure the battery never exceeds a safe operating envelope  even if the BMS allows for this. Well built drop-in batteries use an internal BMS that actually protects the battery from a maximizing cycle life perspective. Batteries built to maximize cycle life will have much more conservative HVC and LVC voltage levels.

TheBMS on this battery is built to maximize cycle life:

Never purchase a drop in battery that allows the cells to exceed 14.6V/3.65VPC or that disconnects below 10.0V/ 2.5VPC

#9 Understanding Cycle Life Claims – When an LFP cell manufacturer rates a cell at 2000 100% DoD cycles this is; charge to target voltage, stop immediately once you hit that voltage, discharge to the low voltage threshold, repeat, repeat, repeat. If this target voltage for cycle life testing is 14.6V they charge to 14.6V, stop immediately and discharge. These cells, at this rating, are not held at a the target voltage for cycle-life testing. In other-words you may not get the claimed cycles using a lead acid charger that holds an absorption cycle timer orcharges differently than the way the cells were tested.

WHAT ABOUT CHARGING LFP WITH OTHER SOURCES?

LFP batteries are charged using a CC/CV profile. This means constant-current/constant-voltage

Bulk = Constant-Current(charge source working as hard as it can see burned up alternators above)
• Absorption = Constant voltage( voltage is held steady for a short time or until current declines to the manufacturers spec.
• Absorption Duration = Once the batteries have achieved the absorption voltage the time the batteries spend  at this voltage must be limited. Many lead acid charge sources spend far too long in absorption and this is not healthy for LFP.

Do you know what this means?

max charge voltage 14.6V

max charge current 20% of installed Ah Capacity

When at 14.6V all charging must stop when accepted charge current has dropped to 0.02C or 2% of installed Ah capacity

Can Your existing charge system do this?

Pay attention to the details!

When installing these LFP batteries in parallel the max charge voltage is just 13.8V-14.2V   (it’s 14.6V for a single battery”details”)
Max charge current is 50% of installed Ah capacity or .5C.
When at 13.8V – 14.2V and charge current has fallen to 5% of installed Ah Capacity all charging MUST STOP

Can Your chargers do this?
Can Your charge sources be programmed for these parameters?

*Drop-In Charge Voltages – Follow the manufacturers guidance!

Some drop-in batteries are not using cells that are impeccably matched. Lithionics would be an exception to this rule but they are obviously a lot more costly.

Unfortunately, with most “drop-in” batteries you don’t really know what is inside, or how well matched the cells or cell blocks are. You’re essentially shooting darts with a blind fold on. Lithionics and Kilovault are in a very small group of manufacturers that take quality & cell matching to the level it should be. Lithionics can actually supply a performance test sheet for every cell in their drop-in batteries.  Battheborn matches individual cell modules(they use cylindrical cells) but not each cell in a module.

Series Solar Warning!

Over the last few years on boats one of the trends that can be a little terrifying has been that solar panel array voltages have been creeping up and up.. Many boat owners want to install their solar panels in series and then run them through an MPPT controller to maximize the energy capture of the array.

This is all well and good until there is an issue and the MPPT controller fails. Imagine what happens if you’re MPPT controller fails and starts passing PV voltage through to the batteries? If your array is over 60V & these are lead acid batteries they will eventually explode. If they are lithium iron phosphate drop-in batteries you will toast your BMS! Once the BMS is been fried by the solar array voltage you have no BMS protection & the solar array will continue feeding dangerous voltage to the batteries until they are destroyed. You can imagine what will happen if this continues to go on after in an MPPT failure. In case you’re wondering yes, these failures have happened and lithium iron phosphate batteries have been destroyed due to this. These failures almost never occur in tier-top tier supplier MPPT’s.

How do you avoid this?

#1-observe the maximum number of series batteries you can wire for. With most brands limit this is 24 V or 48 V. This voltage is typically the maximum SAFE voltage the battery bank BMS CAN handle. So, your PV array should not exceed this voltage.

#2 if you wish if you wish to use series-solar on your vessel you will be safer to split the array into smaller series strings that remain below the batteries maximum series allowable voltage and give them each their own MPPT solar controller.

#3 Use only top tier MPPT suppliers (eg; VICTRON, OUTBACK, MIDNITE, MORNINGSTAR ). These controllers use isolated input/output and  are designed not to fault in a manner that passes full PV voltage through to the batteries..

*Pack Voltage vs. Cell Voltage:

Pack voltage tells you nothing about cell voltage as can be seen below!

Know your loads before you buy!

The critical load data you need to know is the in-rush current for all DC Motors .This includes a windlass, electric winches or a bow thruster. You also want know your inverters Pre-charge in-rush.  Unfortunately most DC Clamp meters cannot properly capture DC in-rush current. We own three DC clamp meters that claim to do in-rush but all except the Fluke meters fail miserably. The image below is one of our Fluke 376 meters capturing the in-rush current for a Lewmar V2 Windlass. This customer ruined his FET BMS (seen in an image above in this article) byusing his “direct from China” drop-in battery to power his windlass. Warranty? Ha-ha now that’s funny….

The image above is a prime example of how drop-in battery bank went wrong for this customer. he wanted to lighten the load in the bow of his sailboat so he installed a single drop-in battery to power his windlass.What he failed to understand was the BMS’s current handling rating . In just a few short weeks he destroyed his drop-in battery with his windlass when he failed to account for what the peak in-rush current handling of the BMS., Warranty? Not covered!

1) Balance current-The sealed internal BMS’s in most drop-in batteries don’t have a lot of balance current to work with, usually mA level currents for balancing. We have even seen some BMS specs suggesting they can only balance the cells at a maximum 10 – 30mA or just 0.010A to 0.03A.If you’re running a 200 or 300Ah @12V battery the cells had better be well matched or the BMS may not be able to keep up….Again, Only buy from reputable Vendors!

2) Ballancing –Ballancing Does not usually start until the cells are exceeding 14.4V or 3.6V per cell. Some are slightly higher and some slightly lower, just depends upon what you bought. Where the cells begin balancing MUST always be specified!If you don’t see this spec ask the manufacturer.. This means that in order to ensure the cells stay in balance they need to get to a balance level at each 100% SoC charge cycle. The reason drop-in makers suggest such high voltages is because balancing is typically done at the top-of charge with a FET based BMS.  KiloVault batteries begin to balance at 14.0V(pack) or 3.5VPC.This is is excellent for cell longevity and iswhy Kilovault can claim 5000 cycles @ 80% DoD….

3) Absorption Duration –The manufacturers, for obvious reasons, want a short absorption voltage duration, some as short as just 2 minutes but many demand less than 30 minutes. With mA level balancing current, two minutes is not a lot of time to re-balance cells so they depend upon the battery getting to the balance voltage with each excursion to 100% SoC. If it does not get to a balancing voltage, the battery cells can become out of balance and the FET BMS may never be able to catch up with out of balance cells..

WHAT YOU WANT TO LOOK FOR IN A DROP-IN?

#1 Externally communicable BMS; at a bare minimum Bluetooth FOR ABYC  “VISUAL”COMPLIANCE.

#2 BMS current handling(in-rush data): You’ll need an internal BMS  capable of handling the amperage’s found on your  boat. If you’re vessel has large DC loads such as electric motors powering winches a windlass or a bow thruster you need to carefully confirm that the drop-in batteries you’re buying can handle these loads. The proper measurement of these motors is not the wattage rating it is the in-rush-current.

 #3 UL Testing -Bare Minimum=Individual cells that have passed UL testing

#4 Third party vibration testing data – UL, IEC or equivalent vibration testing for the entire battery, not just the bare cells

#5 Verification of internal cell matching. Currently Lithionics is the only drop-in battery manufacturer I know of that can physically send you the cell matching testing data for each cell in a battery. With only the batteries serial number, Lithionics can print this report and send it to you. This is the type of data that every drop-in battery maker should be able to provide.

#7 Internal wiring gauge & temp rating specifications

#8 External BMS alerts that can externally warn of a trend towards a disconnect.(Both an ABYC and ISO Requirement)

#9 BMS low voltage, high voltage and over & under temp protection for each of the four 3.2V cells in the battery

 

 

Legitimizing LFP

It’s not just the Chinese who realize they can grab market-share with LFP. After having their “deep cycle“clocks cleaned by LFP, both Trojan and Lifeline battery, two major lead acid players, have entered the LFP market. Having actual lead acid battery manufacturers in this marketplace actually lends credibility to LFP. These manufacturers can no longer ignore it as they have dug their own graves by misleading customers about cycle-life. The manufacturers lifeline and Trojan have partnered with in China are two of the finest drop-in battery manufacturers there are, these are, not elcheapo’s. In the end this is good for the market! Xantrex also now has a battery. Xantrex is no slouch as their parent company is Schneider Electric..

Victron is Also in the Drop-in Market

LFP WARRANTIES ARE Nothing more than lawyer Speak!!

LiFePo4 Marketing:

“Each XXXXX brand Battery is Protected from over-heating, over charging…”

Warranty exclusion reality:

CONSIDER YOURSELF CONFUSED!!

Exclusion: “Damage due to over-charging”

vs. the Marketing ; 

“Each XXXXX brand Battery is Protected from over-heating, over charging…”If you’re wondering how a battery that has a BMS that “protects from over-charging Can be “over-charged” it is pretty simple.”OVER CHARGING CAN BE FROM “OVER ABSORBING”! Lead acid chargers are notorious for over-absorbing !

Of the price-point drop-in batteries, Battleborn is quasi putting their money where their mouth is. They back the battery with a 10 year “manufacturing defect” warranty. (KiloVault is 7.5 years) Please understand that Battleborn is not a 10 year warranty that covers any sort of cycle life. This warranty only covers manufacturing defects. We see it repeated over and over that Battleborn(10 year) or Dakota(11 year) have the best warranty in the industry but that warranty only covers a defect in manufacturing! Defects in manufacturing typically show up pretty quickly. Lithionics for example actually puts a cycle-life warranty on their batteries(currently the only manufacturer we know of that does this-Let us know if you find others).

That said, kudo’s to Battleborn,Dakota, KiloVault and others who put a decent “manufacturing defects” warranty on their batteries. The internal build quality of the Battleborn, is  decent compared to many batteries at this price level,but the Kilovault we believe is better and is less money. We have/cut open a slew of Chinese LFP imports and what’s inside can be HORRIFYING! The only reasonably priced non USA assembled battery we have cut into that we find to be extremely well built are the KiloVault batteries.

Will Your Manufacturer even be around to honor a 5+ year warranty?

The two brands below no longer exist…..

Have you done enough research on a manufacturer?

Could this be a reason why one of the brands from above disappeared?

WHAT ABOUT FLOAT CHARGING & STORAGE?

Float Charging

Float charging is a relic that’s left over from lead acid battery charging. Lead acid batteries directly benefit from being held at 100% SoC. LFP do not benefit from this.. Float charging is not necessary for lithium iron phosphate batteries. The only reason any lithium ion phosphate battery manufacturer even suggest a float voltage is to satisfy end users who want to continue  using legacy/antiquated lead-acid charging equipment . In no way does float charging benefit your LFP batteries. The act of holding LFP batteries at or near 100% SOC can only serve to slowly harm them and eat away at cycle-life. An LFP cell can achieve 100% SOC at just a bit over 3.4 VPC (13.6Vpack  voltage) if you’re battery manufacture suggests anything over 13.6V for float you may want to reconsider that and set it below 13.6V .You can always set it lower but should not go higher.

There are charger manufacturers out there who actually understand charging LFP batteries.Victron  is about the best known. Victron has a specific setting in their custom menu that allows you to set a “storage” voltage this is a voltage the charger drops to after a short float has been done. It can be custom programmed to allow the batteries to self discharge down to about 50% SoC before the charger kicks back in and maintains the “storage voltage.”the only chargers or inverter/chargers we currently recommend for lithium iron phosphate batteries are Victron.

Don’t take my word for it, here is Battleborn….

What About Storage?

As mentioned above lithium ion phosphate batteries do not prefer to be sitting at or near 100% state of charge for long periods of time. This is why you will see, from nearly every single legitimate drop-in battery manufacturer, a recommendation for storing the batteries at or near 50% state of charge or less

Below are snapshots from lithium ion phosphate drop-in battery manuals or specification sheets .

What about “Hybrid ” Systems (Lead & LFP in parallel)?

In one word NO!Sure you can find someone on YouTube to tell you what you want to hear, but this is not always what you should hear…

Reader Challenge:The First reader to bring us (in writing) a US based LiFePo4 Manufacturer/reseller that allows you to place lead and LiFePo4 in Parallel wins $25.00!!Here is where the Eoropean IzSO standards land

ISO/TS 23625

Even Direct from China  Manufacturers disallow it.

From LFP Manuals/spec Sheets

What About Over-Current Protection?

Lithium iron phosphate batteries can throw a ton of current into a dead short but the fuse protecting the wire must have a suitable AIC rating. AIC stands for amperage interrupt current. AIC is different than the fuses trip rating. AIC is the maximum safe-current the fuse or breaker can trip under without having an unsafe-failure. For example if a battery has too much amperage, in a dead short ,Circuit breakers can actually weld-shut before they can trip. This is why AIC matters. The bottom line is that class T fuses are what should typically be used when protecting lithium iron phosphate batteries.

ABYC TE-13

The UL image below depicts a drop-in battery with a FET BMS that is “short circuit protected”. As can be seen this single drop-in battery can stilldeliver over 5500A into a dead short! Now imagine if you have two or three of these batteries in parallel or four+. The short circuit current of a FET BMS is always considerably higher than one would assume it is When in doubt use Class T fuses for LFP.

The reason I’m showing an image of the mega or AMG fuse below is because of the growing popularity of the Victron Lynx distribution systems. These are excellent systems, we love them,however, caution must be used when connecting them directly to a battery bank. In North America over-current protection  needs to  follow the ABYC’s AIC guidance. Mega/AMG fuses are fine so long as they are downstream of A fuse or breaker that is properly AIC rated to handle the batteries short-circuit current. In other words, MEGA/AMG fuses should not be used to directly connect to a lithium iron phosphate as the primary over-current protection as the can only interrupt up to 2000A safely..

Below are the specifications for a blue Sea systems Cass T fuse. Notice the fully encased metal body and the 20,000 A interrupt capacity. Also note that these fuses are rated at 20,000A at 125 V. Tthe higher the voltage the tougher it is to meet in AIC rating. Compare this to a typical ANL fuse which only has a 6000 amp AIC rating at 32V. a class T fuse would have a significantly higher AIC rating@12 V if it was tested at this point because it meets 20,000 AIC it 125 V there was no sense in spending the money to tested at a lower voltage.

I would be sloppy if I failed to mention that any installed fuse should not be sized to carry more than 80% of its rating. This also goes for circuit breakers. This is especially true when installing inverters & charge equipment and especially alternators. For alternators a fuse of at least 140% of the alternators rating should be used. Thankfully , Blue Sea Systems is finally addressing this and putting it in their literature.

In summary, do your homework, purchase carefully, avoid direct from China imports when you can,install your system safely, use good quality charge equipment and you will be happy for many, many years and thousands of cycles.

Good luck and happy boating!

The 1/BOTH/2/OFF Switch

Preface: I’ve seen & read many on the internet suggest that “The 1/2/BOTH is RC/Rod’s/Compass Marine’s preferred switching method”.. Let me be clear on this point; this is not our preferred method, it is simply a method.  This article is only intended to showcase how the 1/2/BOTH switch can be used in an easier and often less confusing manner. Many boat owners don’t have the luxury of starting from scratch and the existing switch can usually be re-used/re-purposed easier, and in a less costly way, than converting to an entirely new switch configuration..

Basic Design Principles for Battery Switching:

1- Bank Isolation – The ability to isolate a battery bank from both loads and charge sources in the event of a bank or battery failure.

2- Cross-Connection Use – The ability to use either on-board battery bank as the sole use bank, meaning it serves as starting and house load bank in an emergency, This design criteria should always include #1.

3- Ease of Use – A battery switching design is no good if the boat owner does not understand it.

One area of confusion we see fairly routinely is a boat-owner misidentifying the 1/2/B switches terminals. A 1/2/B switch has just three terminals and four positions.

Terminals:
Bank 1 – Input stud 1 in photo
Bank 2 – Input stud 2 in photo
“C” Post – Output stud in photo

“But RC where does DC ground connect to on the 1/2/B?”

If I had a dime for every-time this question was asked, I’d not be writing this article. The 1/2/B is switching only the DC positive conductors and has nothing at all to do with DC negative. Please DO NOT connect DC neg to a 1/2/B switch!!

Terminology Used In This Article:

1/2/B – A battery switch that has position 1, 2 OFF and a paralleling feature often called BOTH, COMBINE, ALL or 1+2
C Post – The “C” Post is the COMMON post which is also referred to as FEEDER, COMMON or OUTPUT
Both – When the switch is set to 1+2, BOTH, COMBINE or the ALL position both battery banks are now physically wired in PARALLEL

The 1/2/B Switch is a Very Common Factory Wiring Configuration:

Over the years most all boat builders, of both sail and power, have installed the simple and redundant 1/2/B switch. The switch, I believe, has gotten an undeserved bad rap over the years. Why? It’s really not necessarily due to the switch itself, but rather due to the way most builders install them, and the way many boat-owners have used them.

Despite the bum rap, the 1/2/B switch remains a versatile & redundant single-switch battery selector. Surprisingly, even today, they are still the #1 selling multi-bank switch. The 1/2/B offers more redundancy and isolation than just about any other easy to use configuration. The “easy to use” part is arguably debatable. It should be easy but lack of a complete understanding leaves many boaters confused.

1/2/B Switch Confusion Issues Can Result In:

• Unnecessary Switching & Forgetfulness
• Two Dead Battery Banks at the Same Time
• Damaging Voltage Transients
• Forgetting to Charge a Bank

Confusing Lingo:

START & HOUSE Banks – Like anything in the marine market the 1/2/B can develop it’s own levels of myth & lore. One of the most common misconceptions is that you have a Start Bank and House Bank. Sure, you can assign a switch position to HOUSE and START but they are really EVERYTHING banks. A “START” battery, by definition, is really dedicated to only starting an engine, no house loads.

If you wish to continually move the switch from 1 to 2 then 2 back to 1 etc. etc. it may feel like you have a START & HOUSE bank but you really don’t. In the #1 or #2 position each bank serves both starting and house purposes. Starting and House services cannot be isolated from one another with a 1/2/B unless you add another ON/OFF switch. It is for this reason that we refer to the banks, with a 1/2/B as HOUSE and START/RESERVE. This is still actually incorrect terminology, but a bit more accurate. As you read on you see more of what we mean by this. Technically, and accurately speaking, you have Bank 1 & 2 and each of those positions do both house and starting duties simultaneously.

Builder Blunders?

The 1/2/B switch, as wired by most builders, becomes a Bank Selection and Charge Directing switch. This means what ever position you have the switch set to, is where your on-board energy comes from, and where the engines alternator sends its charge current.

What Bank Selection and Charge Directing Mean:

1/2/B Switch Set To;

Bank 1 = DC loads are drawn from bank #1 and alternator charging goes to bank #1
Bank 2 = DC loads are drawn from bank #2 and alternator charging goes to bank #2
BOTH = DC loads are drawn from BOTH banks and alternator charging goes to BOTH banks
OFF = Both battery banks are isolated/OFF

Note: Even when set to OFF a bilge pump, propane sniffer, stereo memory or VHF may still be direct wired to the house bank so the vessel may still have live 12V wires..

Typical Factory Wiring:

Most boat builders simply wire the alternator circuit back through the starter feed wire to the “C” or common post of the battery switch. The “C” post is energized when you flip to 1, 2 or BOTH and is isolated or disconnected when you switch to OFF. This wiring method is cheap & easy for the boat builder, but leaves owners with lots of room for human error and misunderstandings.

The factory wiring works simply, and allows you to choose which bank you are charging or drawing from by selecting that bank, or both, on the switches face-plate. In the drawings below, the green lines are showing the 1/2B switch connecting the alternator, starter motor and the  DC panel loads, to the bank or banks selected, via the “C” post of the battery switch. You can visually see the path the alternator takes to get back to the battery bank. The green lines represents the switch position.

Set it to bank #1 and bank #1 gets charged/discharged. (Follow the green line)

Set it to bank #2 and bank #2 gets charged/discharged.

Set it to BOTH and both banks get charged/discharged.

Mishaps and Human Error:

Mishaps and human error creep in when an owner forgets to manually switch & charge bank #2 and now bank #2 never gets charged.  Far too often an owner will leave it on BOTH, and then run both the banks completely dead. If this happens, and it does, you’re $hit out o-luck…. We call this the Human Error Factor or HEF.

Owner Blunders?

So why may the factory wiring method be a poor choice? It’s not necessarily poor choice, if you understand your system and how to use it.

Human Error Blunders;

Blown Alternator Diodes & Voltage Transients:

This big blunder happens when you, or a crew mate, tries to switch to another bank and pass the battery switch through the *OFF position, even momentarily. With the engine running and the alternator charging this creates an open-circuit between the alternator and the load (load = battery bank) it’s charging. Momentarily passing through OFF, or disconnecting the load from the alternator, can cause a massive voltage spike as the load/ battery bank is disconnected from an alternator. This quite often results in damaging the alternators rectifier diodes & rendering it non-operational near instantly. it can also damage sensitive electronics that are connected to the “C” post of the switch.

*Most quality 1/2/B battery switches, from reputable manufacturers like Blue Sea Systems, BEP/Marinco, Guest & Perko, are designed to be make-before-break. Make-before-break means that as you turn the switch from position 1, to BOTH or 2, the previous position does not open-circuit or disconnect until the next position can carry the current.

As some battery switches age they can wear and become break-before-make. For this reason it is not a good idea to move the switch while the engine is running unless you perform an occasional make-before-break test. The best way to test your switch is to turn on the cabin lighting (incandescent bulbs work best not LED’s) then slowly rotate the switch from 1 to BOTH to 2. If the incandescent light/s flicker at all during this rotation, replace the switch. Even a fraction of a second disconnect is enough to cause an alternator load-dump.

The Load Dump:

Picture, if you will, a Top Fuel Dragster. The drag car is moving at 200 MPH when it smashes directly into a 10′ thick solid concrete wall. All that energy/mass, and no where to go, means instant destruction. The concrete wall is akin to what happens in your alternator when you shut the battery switch off during charging, especially high-current bulk charging. This open-circuit event, between the battery and alternator, acts as the concrete wall and all that energy has nowhere to go. The result with an alternator is that this energy has to go somewhere, so it skyrockets the voltage instantaneously. The result of an open-circuited battery switch is called a load-dump. A load-dump creates a very fast voltage spike/transient that can destroy the rectifier diodes. Here at Compass Marine Inc., we repair quite a few alternators each year due to battery switch load-dump blunders.

Ever wonder why a 1/2/B switch has this warning? Well, now you do…

Damage to Sensitive Electronics:

Unfortunately it’s not just alternator diodes we need to be concerned with, in a battery switch disconnect / load-dump. A lack of charging is what most owners notice first, but the damage may not end there. If you take a look at where your DC loads are connected, this just happens to be the same exact place as the factory wired alternator, the c-post. When the switch is accidentally opened, while charging,  the alternator is instantly disconnected from the battery and all that energy has to go somewhere. Where does it go? Follow the diagram below and you’ll see.

The voltage transient/spike that’s created by accidentally opening the battery switch, while charging,  goes straight into your sensitive DC electronics because the alternator and DC panel are connected to the same c-post stud, which is no longer connected to the battery/load.  The voltage transient from a battery switch disconnect often destroys the alternator diodes and it can also damage or murder your sensitive DC electronics. It’s not uncommon for us to find multiple other items damaged when a customer comes to us for a bad alternator, and the diagnosis is blown rectifier diodes.

In theory, the voltage regulator would react and stop this voltage transient, after all they do limit voltage, but the spike happens far too fast for the voltage regulator to react. This damaging transient occurs in microseconds. As you now know, when you open the battery switch, while charging, there is a high likelihood the diodes in the alternator will be blown. A mistake like this can leave you with no alternator and potentially ruined navigation electronics too. Sadly the factory wiring does nothing to limit or protect against this. Some newer alternators, on late model engines, utilize avalanche-diodes. Avalanche diodes are more durable and designed to limit the voltage transient, but most existing marine alternators do not utilize avalanche diodes..

Alternator Field Disconnect:

Some battery switches even feature an Alternator Field Disconnect or AFD feature. The AFD consists of two terminals that break the alternator field or external regulators power wire slightly ahead of the 1/2/B’s OFF position opening. Unfortunately, most vessels with see with AFD switches are either not using it or the AFD circuit is wired incorrectly. If you don’t have access to the field wire, inside the alternator, the AFD feature does you no good.

We’ve even seen alternators where the factory alternators key-on excite-wire was passed through the AFD circuit yet the diodes were still blown. Why? The excite wire is only needed to get the alternator started. Once the alternator is spinning, and producing power, cutting +12V to the excite-wire does not always de-power the regulator, and the alternator keeps on chugging away.

Alternator Protection From Load-Dumps:

If you wish to keep your 1/2/B factory wiring, and you understand the nuances, it would be a very wise idea to install a Sterling Power Alternator Protection Device. The Sterling APD is designed and intended to clamp or limit a voltage spike/transient to a safe level and protect both the alternator and other DC components.

Here the Sterling Alternator Protection Device is shown with a LiFePO4 drop-In battery. Drop-In LiFePo4 batteries have internal BMS switch (battery management system switch) that can essentially do the same exact thing as flipping a 1/2/B switch through the OFF position. Installation is as simple as two wires and a fuse, and it’s inexpensive insurance.

The “I Must Set it to BOTH to Start the Motor” Mind Set:

Sometimes blunders are just caused by a cascade effect. The “I Must Set it to BOTH to Start the Motor” is typically flawed and unnecessary. At the same time, it’s a reality in some owners minds because the BOTH position acts as a Band-Aid for weak batteries or a poorly wired system.

In the case of starting a motor, the BOTH position is typically hiding or covering up other issues and does not actually solve the issue at hand. On the flip side, it leads to a cascading effect where forgetfulness can lead to error. The “You must use BOTH to start.” mantra has actually climbed to urban-myth status level.

You Should Not Need to Use BOTH to Start Your Motor!

If you need BOTH banks to start your motor, you have other issues such as:

• Failing Batteries
• Batteries Not Sufficiently Sized to Start Your Engine
• Bad or High Resistance Terminations in Your Battery Wiring
• Undersized Starter Motor Wire
• Failing Battery Switch
• Dirty or Corroded Terminals
• Faulty Starter Motor
• Wiring issues in the starter solenoid circuit

In most cases your engine can easily be cranked by the house bank. Keep It Simple..

“But RC engine cranking uses lots of battery capacity, isn’t this bad for a house bank?”

Lets examine the actual math on this one to hopefully explain the misnomers surrounding engine cranking. Compass Marine Inc. has invested in the expensive tools that can measure engine cranking performance with high precision. The average cranking duration’s we measure, as defined by a loaded to un-loaded starter motor, is 0.65 to 1.5 seconds. The math & images below are from starting a 44HP diesel motor at 32F with a deep-cycle house bank. Most boaters will never start a marine diesel at 32F.

The math on how much energy is actually consumed from cranking is pretty straight forward:

0.75 Seconds is approx 0.002 hours – 286A X 0.0002 = 0.06 Ah

1 second is approx 0.0003 hours – 286A X 0.0003 = 0.086 Ah

2 Seconds is approx 0.0005 hours – 286A X 0.0005 = 0.14 Ah

3 Seconds is approx 0.0008 hours – 286A X 0.0008 = 0.23 Ah

4 Seconds is approx 0.001 hours – 286A X 0.001 = 0.28 Ah

5 Seconds is approx 0.0014 hours – 286A X 0.0014 = 0.40 Ah

We’re not just shooting from the hip on these numbers. The images below show the entire story..

Resting Bank Voltage > Tested CCA of The Bank > Rated CCA of Each Battery > Battery Case Temp

As can be seen above, when we parallel deep-cycle batteries rated at only 675 CCA, we wind up with 2071 CCA for cranking at 0F (these batteries were preforming slightly better than 675 CCA). This screen translates the 32F temp to a 0F CCA rating. When the batteries are warm the cranking capability is much greater.

Cranking Current Graph for Entire Duration of Starting Event

In the image above we can see how this very cold 44HP engine drew slightly over 640A for the in-rush, but the cranking amperage declines rapidly after the initial in-rush.

Averaged Voltage, Averaged Cranking Current, Duration of Start  (Loaded to Unloaded), Circuit Resistance

The screen shot above summarizes the averages. Despite a 640A+ peak in-rush the averaged cranking current, from loaded to unloaded starter motor, was just 286A and the total cranking duration was just 0.765 seconds or 765 mS. For what it is worth, this particular bank is protected by a 300A fuse and has done well in excess of 1200 starts, over a 12 year period, and never once nuisance tripped the fuse. Why? Because the duration of a starting event is very short, this one 3/4 of a second, and this does not even come close to the trip-delay curve of the fuse.

Engine Cranking Reality:

There is little dire need on most smaller boats, especially ones with small aux diesels (sub 150 HP) or gas engines, to require a *dedicated starting battery.

*Dedicated Starting Battery – A hard wired battery bank used only for starting purposes and nothing else, unless for emergency situations. A dedicated starting battery is connected directly to the starter motor when the start battery switch is on.

A dedicated starting battery is always nice, but it usually means a new switch and wiring reconfiguration to do it correctly. With many battery switches located in DC panels, & these are usually not ABYC compliant, this is often not an easy undertaking. By tweaking the existing 1/2/B, & how you use it, you can make the system more fool proof and easier to use.

A large chunk of our customers boats have started engines, for years, on their house banks, we’ve now seen the math as to why this is so and why this works. We even have commercial fishing boats starting large Cummins, Cat and John Deere engines with 6V Golf Car batteries.

How? To grasp this we need to understand that a house bank is typically much, much larger than a start bank. Because of this, and even when the batteries are deep-cycle, the house bank almost always has more cranking capacity than the single, & typically small, starting battery.  When we parallel batteries, in a house bank, we the cranking capacity is additive. For example, three 100Ah 600 CCA deep-cycle batteries quickly become 1800CCA when wired in parallel.

For owners that understand how to use a 1/2/B, in a more simple manner, this means they only use position #1 (HOUSE) and OFF. The only time to do anything different is when there is an emergency or to occasionally test the reserve-bank to ensure it is still performing well. The 1/2/B works really well as a USE SWITCH, but it can be tweaked to be better.

“But RC the guy down the dock says deep-cycle batteries cannot be used for cranking.”

Sadly, your dock-expert is misleading you on this. I will let Trojan Battery sum this one up.

The key here is “a deep-cycle battery“, meaning single battery, and when most all house banks on boats over 25 feet these days are using multiple deep-cycle batteries you now have many more cranking amps in the house bank than you do in your typical starting battery. Even at 50% DoD a typical house bank will still have more cranking capability than a single starting battery. Unless you have massive diesel engines, or a very small single battery house bank, keep it simple and just crank off the house bank. You can now delegate bank #2 as a reserve/emergency bank.

The Cascading HEF : “I Forgot to Switch From BOTH Back to HOUSE“

The use of BOTH to start you motor, or when charge directing, requires that you remember move the switch off of the BOTH position when you shut the motor off, or shortly after. Unless you need to be in BOTH for charge directing, there should be no other need for this position, in a well operating system, that’s also properly wired. As discussed above, unnecessary switching can lead to potentially blown alternator diodes, damaged electronics or two dead banks as opposed to just one. Using the BOTH position to start the motor is indeed unnecessary switching that can lead to human error issues.

An expensive scenario is that happens all too often, is when an owner has forgotten to switch off of BOTH and killed both banks. Doing this leaves no second / reserve battery to start the motor with. You’d be surprised how many calls we get each year for this exact issue.

Don’t Blame the Switch:

The normal human tendency, when these blunders or HEF happens, is to blame the “stupid” 1/2/B switch. The 1/2/B switch is like a gun, the gun did not pull the trigger, the owner of the gun did. How is the switch “stupid”? It’s not, but the owner may be. How is the switch “stupid” when the owner makes a mistake? It’s not, it did exactly as it was set & wired to do, but the 1/2/B is still often blamed for owner ineptitude.. This is the bad rap we referenced earlier.

Let’s Make the 1/2/B Easier & More Fool Proof

The 1/2/B as a USE SWITCH:

Converting a 1/2/B to a  USE SWITCH is actually quite easy and minimally cost invasive. Once you do this it becomes a SIMPLE ON/OFF scenario. That’s it, ON & OFF, or more accurately #1 & OFF. Once converted to a use switch it is no longer a charge directing switch, or a start on BOTH or #2 then remember to move to #1 switch. It is basically an ON/OFF switch.. Simple, effective and you likely already have one if you’re reading this.

Wiring Upgrades:

The 1/2/B switch is a very useful device and there are a few small changes you can do that can make it even more fool proof. Most of what you need for a very simple and redundant system is already there, so there is little need to spend more money on new switches or drill yet more holes in your boat over what you likely already have. This is of course predicated on the fact that you are comfortable with the idea of not using a dedicated starting battery.

Below Are Illustrating 1/2/B Switch Upgrades in Multiple Levels:

Level 1 Upgrade: In the image below we have the Level 1 Use Switch Upgrade. It consists of adding a Charge Management Device, in the case of this article we have chosen to illustrate the Blue Sea Systems ACR. Once installed the ACR will provide for fully automated charging of both banks. The addition of the ACR eliminates the need to move the switch for charge directing. We’ve also added some fuses, which are required under ABYC standards. Please read our article on Automatic Combining Relays for a better idea of how they work.

You don’t have to use an ACR and the class of “Charge Management Devices is now quite vast. You could also use an:

• Balmar Digital Duo Charger
• Xantrex Echo Charger
• Sterling Power ProBatt Ultra DC to DC Charger
• Victron Orion TR Smart DC to DC Charger

The ACR just represents an excellent low cost option.

Making Sense of Automatic Charging Relays (LINK)

Any bank that can be called upon to start a motor, and with a 1/2/B that is either bank, should ideally have a fuse capable of doing so without nuisance tripping. The bare minimum fuse size, for small diesels, would be 250A but preferably 300A as the minimum. The start bank can also be fused on smaller diesels, but it’s not technically a requirement, under the ABYC standards, to fuse the cranking circuit.

Level 2 Upgrade: In level 1 we reduced the need for unnecessary switching for charge direction by adding a Blue Sea ACR. Unfortunately level 1 leaves open the possibility of a load-dump. The Level 2 upgrade adds a Sterling Power Alternator Protection device to protect against a 1/2/B induced load dump. The alternator is still wired in the factory configuration and we only add an ACR and Alternator Protection Device. You can now get on the boat set the switch to Bank #1 and use the boat. When you’re done flip the switch to OFF. No need for unnecessary switching and human error induced blunders are drastically reduced..

Level 3 Upgrade: The level 3 upgrade wires the alternator directly to the house bank with proper fusing rated at 150% of the alternators rated output and within 7″ of the house banks positive terminal. This upgrade offers optimal charging performance when an owner has an alternator with an external regulator. Wiring direct to the house bank means the alternator cannot be “load-dumped’ by the switch because the alternator is now directly connected to the “load” or bank.  The charging performance aspect is realized by the voltage regulator now sensing voltage closer to the bank and this improves fast charging performance. With a 1/2/B in factory wiring configuration the closest you can sense voltage for the alternator is the c-post of the switch. This typically means less than stellar charging performance. For more on this please read:

Alternators & Voltage Sensing – Why It Matters

There are numerous performance benefits for alternator charging when direct wiring the alternator to the house bank. These benefits are above and beyond the elimination of a 1/2/B switch load-dump. There are however some important nuances to the Level 3 upgrade. If you look closely you’ll notice that we’ve moved the ACR connections & alternator input to the load side of the house and start bank fuses.

The reason for this is rather simple. In the event of a bank failure, and we see them, you will want to be able to keep the alternators charging output with the good bank. This can be done simply and easily by removing the house or start bank fuse. The removal of the fuse  allows you to 100% isolate the bad bank yet keep alternator charging with the now “reserve” bank.

In the event of a house bank failure you would simply pull the fuse on the house bank and set the 1/2/B to BOTH. The alternator can now charge the start/reserve battery, and the entire vessel can run off that bank while the failure of the house bank is dealt with. An even better approach, than pulling fuses, would be to place an ON/OFF battery switch right after the house bank fuse inside the battery compartment.

What if I want to keep my 1/2/BOTH and have a dedicated start battery?

Actually this is pretty easy. In the diagram below we’ve taken the Level 3 upgrade and simply added a Blue Sea Systems ON/OFF battery switch. This design means you retain the ability to start off the house bank in an emergency as well as maintain all the safety and isolation features the 1/2/BOTH can offer.
The diagram below is one that works well when an owner  desires a dedicated starting battery but also want to retain the flexibility & isolation of the 1/2/BOTH switch.

Simply flip to #1 and ON and your ready to go. When you’re done flip both switches to OFF. Label them carefully, Blue Sea Systems sells the perfect labels.

Use Modes:

For customers with this set up I simply leave a copy of all the scenarios of switch use on-board. This is what it looks like..

NORMAL EVERYDAY USE:

ISOLATED START & HOUSE
Note: Alternator charges HOUSE and ACR charges START.
1/2/BOTH = #1
ON/OFF = ON

EMERGENCY SCENARIOS:

START & HOUSE PARALLEL
Note: This overrides the charge management device & allows more current to charge the START bank.
1/2/BOTH = ALL
ON/OFF = ON

Emergency Situ #1 – START – Provides HOUSE & START Duties:
Note: Use if the HOUSE bank were to fail. This 100% isolates the HOUSE bank & uses the START bank for everything.
ON/OFF = ON
1/2/BOTH = ALL
Remove House Bank Fuse

Emergency Situ #2 – HOUSE – Provides HOUSE & START Duties:
Note: Use if the START bank were to fail. This isolates the START bank & uses the HOUSE bank for everything.
ON/OFF = OFF
1/2/BOTH = ALL

The 1/2/BOTH with an additional ON/OFF  is certainly more complicated but more flexible than some other systems. Some battery switches such as the Blue Sea System Dual Circuit Plus force you to use the “combine” feature in an emergency, where you may be paralleling a perfectly good battery bank with one that has an internal short.

Combine as your only emergency option is absolutely not the same as the ability to 100% isolate a bad bank. This image is why you don’t want to combine a good battery to one that has failed or shorted internally. The runaway battery had already been identified and disconnected from the rest of the bank and yet it was still registering 154F.

You Have Lot’s of Options

Before you throw your hands in the air, and potentially throw out a perfectly good battery switch, consider making your 1/2/B switch a USE SWITCH. The 1/2/B as a use switch is still not our favorite switching configuration, but it is often the least expensive upgrade. The upgrades listed above are inexpensive, easy, eliminate needless switching and make the system easier to use.

The options for battery switching are almost limitless, but please always design for:

1- The ability to completely isolate a bank (paralleling with a potentially failed bank is not a suitable option)

2- The ability to use the vessels second bank, for everything, in an emergency

3- Keep it simple & easy to understand.

Good luck and happy boating!

Incorrectly Wired Service Disconnect Switch

This article is part of an on-going series on marine alternators. Our other articles can be found in the link below:

MarineHowTo.com Category – Alternators (LINK)

Terms used in this article:
Alternator B+ = Positive Alternator Output Wire
Alternator B- = Negative Alternator Output Wire
Regulator B+ = Red regulator power wire for the MC-614 (terminal #2)
Regulator B- = Black wire in regulator harness used for negative power and voltage sensing (terminal #1)
Load = Battery Bank
Full Field = Alternator regulator driving the maximum field
ASD = Alternator Service Disconnect Switch
AFD = The Alternator Field Disconnect feature found on certain battery switches

What is the purpose of a Service Disconnect Switch?

The service disconnect switch is designed to disconnect the alternator B+ wire from the battery so a service technician cannot short a wrench to the B+ stud while working on the engine. It is there to help service technicians isolate the alternator from the battery bank, that’s it.

Why would my alternator be directly wired to the battery bank?

When wiring any high performance marine alternator & regulator the optimal charging performance will be realized when wired in the following manner:

• The alternator B+ & B- are directly wired to the house bank or the bank that gets routinely discharged the most
• The alternator regulators voltage sensing circuit is directly wired to the same bank the alternator is wired to

If your paying attention to the wiring laid out above, you’ll quickly realize that even with the main battery switches set to OFF the alternator regulators B+ / power wire still has live power from the house bank. This can be dangerous to a service technician who may be working on your engine and not know or realize the alternator is direct wired to the house bank. Don’t worry, there is an easy way to handle this and it is called an Alternator Service Disconnect Switch or ASD..

Service Disconnect Switch Best Practices

1. Should be mounted near engine, in the engine bay (out of sight of your on-board guests)
2. Should be clearly labeled as an “ALTERNATOR SERVICE DISCONNECT“
3. The power for the regulator must be wired on the alternator side of the service disconnect switch!
4. Use the ASD switch only when servicing the engine

Yes, #3 is bold for a very good reason. The most critical aspect of wiring a service disconnect switch, and one that is far too often over-looked, is to ensure the external regulator cannot boot up with the alternators B+ terminal disconnected from the load or battery bank. This means placing the regultors power wire on the alternator side of the ASD switch circuit so that when the ASD is off the regulator is also off.

“Rod, Why on Earth does that matter if the alternator is disconnected, isn’t it disconnected?”

The answer to the above question simple:

Darrell the diesel guy is working on your fuel injection system and he notices that you have an alternator service disconnect switch and OFF it goes.. Darrell knows what an ASD is, because it is CLEARLY LABELED and turns it OFF, while working on the engine, so he does not weld a wrench to the manifold. When Darrell is done servicing the engine, he cleans up, closes the engine bay, but forgets to flip the ASD switch bank to the ON position. D’oh!!

A few hours later you arrive to use the boat. You fire up the engine and think; “wow this baby is really smooth“. A few minutes later you get a whiff of that acrid electrical burning smell……. Ohhhhh…..

If the alternator B+ is physically disconnected from the battery bank, but the regulator is still allowed to boot up, with no “load” on the alternator, the regulator will go to full field and voltage will shoot through the roof. The alternators rectifier diodes are only rated for so much voltage and your expensive alternator can literally have all the smoke escape from it. Not good!

Correctly Wired Service Disconnect Switch – Balmar MC-614

In this image the regulator B+ / Terminal #2 has been moved to the alternator side of the ASD switch. Even if Darrell forgets to turn it back on, the regulator cannot boot up.

An ASD is an excellent way to keep your performance alternator system safe for yourself or service technicians who may be working on the engine. It will also allow you to yield the alternator performance you’ve paid for. For the most part, perhaps 99.9% of the time, this switch left in the ON position. The only time an ASD is used is when servicing the engine. However, in that 0.1% occasion that Darrell forgets to turn it back on, you don’t want to ruin your alternator by having the regulator boot up into a no-load situation.

The Balmar MC-614 external regulator is unique in that it has a separate positive voltage sensing terminal (terminal #9). This means the regulator B+ / Terminal #2 power wire can be installed on the alternator side of the ASD, and not negatively impact charging performance. For more on voltage sensing for optimal chaging performance, please see this article:

Alternators and Voltage Sensing (LINK)

What About the Balmar ARS-5?

With a Balmar ARS-5 regulator, the regulator B+ / Terminal #2 is also your positive voltage sensing circuit and sensing the back of a switch, one that is so close to the alternator, eats away at your quick-charging performance. For a Balmar ARS-5 regulator it will be best to route regulator B+ / Terminal #2 through the AFD circuit (alternator field disconnect), of an AFD equipped battery switch, and then onto battery bank positive terminal or the always on / charge bus. The Blue Sea Systems 9004e is a simple ON/OFF switch with an AFD circuit.

The drawing above also includes an “Always On / Charge Bus”. A busbar like this is a great place to install fusing, such as busbar mounted MRBF fuses. The Always On / Charge Bus is a great place to collect all your charge devices such as alternators, chargers, solar, wind as well as bilge pumps or other devices that always remain ON.  A busbar like this helps keep the battery bank free of clutter and limits the need for multiple-lug-stacking.. Fusing is always required at the battery end of an alternator circuit not near the alternator.

The Sterling Power Pro Batt Ultra DC to DC Charger

In our continuing series on CMD’s or Charge Management Devices, this article examines and looks at the benefits of the Sterling Power DC to DC chargers and examines the installations where you may find them useful.

*This article includes the latest Sterling Power Pro Batt Ultra series of battery to battery chargers. The latest model is identified by the green stripe across the top of the face plate label.

Definitions Used In This Article

• Battery to Battery Charger – A DC to DC charge source used for charging one bank of batteries from another bank of batteries
• B2B – Short form for battery to battery charger
• DC to DC Charger – A  battery charger that operates from one DC battery bank to another
• CMD – Charge Management Device/s – Devices used to charge from battery to battery or alternator to battery
  
• Target Bank – The bank the B2B is feeding its output current to
• Source Bank – The bank the B2B is getting its input current from
• LiFePO4 – A lithium-ion battery chemistry – Lithium Iron Phosphate
• LFP – Short hand for LiFePo4
• BMS – A Battery Management System is the protection device for an LiFePo4 battery.

The Sterling Pro Batt Ultra B2B Charger

The above photo illustrates how the Pro Batt Ultra comes out of the box. It includes, as standard equipment, a battery temp sensor for the target bank/battery. The 12V to 12V BB1260 is shown and it’s quite small, much smaller than a 60A shore based charger. Size cab be scaled by comparing it to the battery temp sensor on the left. The small size means it can fit many places a standard AC to DC shore charger may not.

“Why Would I Want or Need a Pro Batt Ultra Battery to Battery Charger?”

The Pro Batt Ultra is the most feature filled, fully programmable DC to DC charge management device in existence today. On top of the cram-packed feature set they are actually priced quite reasonably. Compare what the Pro Batt Ultra is capable of, then compare it to other CMD’s that can’t do half of what the Pro Batt Ultra can do, and you see how good a value this charge management device is. Feature wise, the Pro Batt Ultra actually beats the very good Sterling Pro Charge Ultra shore chargers, and these are very good shore power chargers. The Pro Batt Ultra allows an owner to customize the absorption duration, a very useful feature when dealing with LiFePO4 batteries or even some lead acid and it also has dedicated voltage sensing. These are features not found in many AC chargers even at 3-4 times the price. While we can’t really compare a DC to DC charger to an AC to DC charger, output side charging features count no matter what the charge device is.

When You Would Use a DC to DC Charger vs. Other CMD’s

• Differing On-Board Battery Types/Chemistries – eg: GEL House > AGM Start or AGM Start > LiFePO4 “Drop-In” etc.
• Differing On-Board Bank Voltages – eg: 12V House > 24V Windlass or Thruster Bank or 24V House to 12V Navigation Electronics Bank

What is a Pro Batt Ultra?

Very simply put the Pro Batt Ultra is an extremely full featured battery charger, more so than most AC powered shore chargers you’ll find. That’s it. The only difference between a shore charger and the Pro Batt Ultra is that the Pro Batt Ultra can be powered by another battery bank so that it can be used with all your charge sources to charge the target battery.

Pro Batt Ultra = Buck or Boost

The Pro Batt Ultra can not only “buck” voltage (buck means reduce beyond input) but, unlike most DC to DC chargers, it can also “boost” voltage (boost means increase beyond input). CMD’s such as an ACR/VSR/Combiner, Echo Charger or Digital Duo Charger can only reduce voltage to the target bank and can not increase it. None of the aforementioned CMD’s can float a target bank independently from the source bank but the Pro Batt Ultra can float independently.

For example the Pro Batt Ultra 12V to 12V models can take an input of 14.1V from a source bank and output a higher voltage to charge the target bank that may require 14.8V. Another major plus is the Pro Batt Ultra is available for both like voltage and for mixed voltage vessels where both 12V and 24V banks are installed.

Output Current vs. Input Current: Please be aware that unlike a shore based charger, the Sterling B2B chargers are rated based on max input current. In other words a BB1230 is not a 30A output but rather a 30A input. You will get less than 30A on the output side. This is done so you know the maximum the unit can pull from the “source bank” which is a critical measurement to know. The average efficiency of the Sterling B2B chargers is about 86%, but depends on the input voltage.

Pro Batt Ultra Models Include:

BB1230 – 12V 30A Input to 12V Output

BB1260 – 12V 60A Input 12V Output

BB122470 – 12V 70A Input to 24V 35A Output

BB242435 – 24V 35A Input to 24V Output

BB241235 – 24V 35A Input to 12V 70A Output

BB123670 – 12V 70A Input to 36V 23A Output

BBURC – Remote Display for Pro Batt Ultra

What’s the difference between a DC to DC charger and a shore charger?

An AC powered shore charger needs AC power as the input in order to operate. When at sea this means you’d need an AC generator to run your shore charger. The Pro Batt Ultra B2B does not require AC power and instead requires only a DC input.

The Pro Batt Ultra can be used with any bank that’s being charged by another source such as alternator, *solar or a shore charger.

*If large enough to satisfy the input requirement

What Can it Do Differently Than an ACR/Combiner/VSR, Echo Charger or Digital Duo Charger?

• Can independently float the target bank even when the source bank is in bulk or absorption
• Provides a true multi-stage smart charging algorithm completely independent of source bank
• Has a built in voltage sense circuit
• Has a battery temp sensor as standard equipment
• Can be fully custom programmed including absorption, float, absorption duration on/off points etc.
• Can be activated via ignition excite or automatically by voltage
• Can accept a BMS trigger signal from a LiFePO4 battery BMS
• Can withstand a load dump from a an opened battery switch or a Lithium-Ion BMS Load Dump
• Can reduce or increase the charging voltage to the target bank eg: 14.1V GEL House and 14.7V TPPL AGM Bow Bank
• Can charge a 24V bow bank from a 12V House bank
• Multiple models: 12V input & 12V output, 12V input & 24V output, 24V input & 24V output, 24V input & 24V output
• Is an excellent CMD for use with mixed on board chemistries including lead-acid and LiFePO4
• Is an excellent CMD for charging a 24V bow bank from a 12V house bank.
• Is an excellent CMD for charging a 12V electronics bank from a 24V house bank.
• It is not just a simple “voltage follower” like an ACR, Echo Charger or Digital Duo Charger, it is an actual DC to DC battery charger

Mixed On-Board Bank Voltages:

12V to 24V Charging – BB122470:

The scenario below is quite common on vessels using large DC bow thrusters or larger windlasses or winches. Until now charging a 24V bow bank from a 12V source was a bit of a kludge work around often requiring running a genset and an AC shore charger. The BB122470 is an ideal tool for this type of bank layout where the house bank is 12v and a bow, start, winch or thruster bank is 24V. The Pro Batt Ultra BB122470 makes easy work of this and gives a true multi-stage charge algorithm to the target bank.

In a 12V to 24V situation the BB122470 can be placed closer to house bank, where the input wire needs to be large and handle 70A, and then a smaller gauge 24V output wire can be run to the target bank along with a voltage sense wire and the temp sensor.

24V to 12V Charging – BB241235:

On larger boats it’s not uncommon to have a 24V house bank and a 12V bank to supply 12V marine navigation electronics. In this scenario a BB241235 is being used to charge a navigation electronics bank from a 24V bank of house batteries.

The flexibility of the Pro Batt Ultra is really quite amazing compared to what we’ve had in the past regarding mixed bank voltages.

Typical Installation Consideration for the Sterling Pro Batt Ultra

Wiring

In this image we have a BB1230 being used to charge a start battery from the house. Because the Pro Batt Ultra’s use *pressure plate terminal blocks, meaning bare wire is inserted and the screw tightened, you really want to ensure the wires are properly secured as close to the unit as is feasible. The BB1230 is capable of accepting 6 AWG marine wire and here we’re using 6GA wire.  Each 6 GA wire is secured with wire tie mounts & wire ties to secure each wire within a few inches of the unit. The wiring is also labeled to identify it including the voltage sense wire and the temperature sensor.

*The use of pressure plate terminal blocks should ideally mean they are ABYC compliant and that a “screw” does not impinge upon the bare wire strands. The Pro Batt Ultra’s use internal “plates” that compress the wire and no direct screw is twisting on the wires during torquing making them ABYC compliant.

PRO TIP: With pressure plate terminal blocks, and finely stranded marine wire, it is best to snug the wire, then wait a bit, and snug it once more. The finely stranded wire can slowly compress into shape and the original clamping pressure can decrease.

Because the terminals accept bare wire it is recommended to use tinned wire. Tinned wire is not an ABYC requirement, but it certainly corrodes much less rapidly than bare copper.

Wiring of a Pro Batt Ultra should comply with ABYC E-11 standards

• Fusing input & output positive wires within 7″ of each battery bank (Min fuse size should be 125% of input rating)
• Proper strain relief & wire support
• Chafe protection where necessary
• Wire bundling considerations
• Placement of unit in relation to batteries or moist areas
• Wire labeling
• Use of proper crimp tooling & terminals
• Temp Sensor Placement (negative battery terminal or battery case only)
• Over-Current Protection for Voltage Sense Wire within 7″ of battery positive
• Proper gauge wiring for the amperage (ideally not to exceed 3% voltage drop)

In the wiring example below we have a typical cruising boat installation with all charging feeding the house bank. It is set up for automatic voltage activation. Once the house bank hits 13.2V the B2B will boot up and begin charging the target bank.

As can be seen above the typical marine installation is just 5 total wires or 6, if you purchase the optional remote display:

• Temp Sensor
• Volt Sense
• Output Positive
• Input Positive
• Negative
• Remote Display (optional)

You may be wondering why we took so many man-hours to create all these diagrams? The answer is actually quite simple, the Sterling Power manuals are rather difficult for most owners to make sense of. Even we had to send Charlie Sterling a rather long list to get clarification on some of the wording. Please understand that Charlie is an electrical engineer, and writing manuals for the non-electrical engineer boat owner can be very difficult, to convey clearly, to a DIY. Sterling is not alone in this regard and it is common in the industry. We know the manuals can be difficult because we get the support calls & emails before our customers ever reach out to Sterling Power. Almost always it is just a misunderstanding of the instruction manual, not an actual problem with the product.

Sterling Powers main market for the Pro Batt Ultra is for “caravans“, or RV’s & Trailers to those of us in the USA. In order to cater to this market the product needs to be in compliance with the Euro 6 Emission Standards. In Euro 6 installs the B2B’s are connected to the vehicles starter battery and feed the trailer or RV’s hotel/house battery bank. Due to Euro 6 regulations you can’t really tinker with the alternator and many of these are now controlled by the vehicles CPU to work in concert with regenerative braking etc..

The Pro Batt Ultra allows for regenerative braking / Euro 6 compliance. In short, the stock alternators do a horrible job of charging deeply cycled house banks in the trailer or RV, and you can’t really modify them. The good news for Euro 6 installations is the auto and RV recreational industry typically over-size most alternators, and this results in a very low warranty rate. It also means there is room left over, in terms of amperage, for the B2B charger to pull from.

Bottom Line on the Owner Manual?

For a marine application please ignore the vast majority of the Pro Batt Ultra manual that primarily deals with Euro 6 compliance. We have asked Sterling Power for a Pro Batt Ultra marine only manual but so far no luck.

Input Bank Charge Source Sizing:

Lead Acid Alternator Sizing – Sterling Power recommends that your alternator be sized (based on its SAE output rating) to be at least 30% larger than the B2B unit you choose. In our testing we found 30% to be a bit low for many “stock” alternators and find that double the B2B size means a much cooler running alternator. The reason for this is actually quite simple, you don’t want to tax your small alternator to death. Alternator output also varies based on RPM and winding temp. We see small alternators taxed to death quite regularly on boats.

Unlike automobiles, marine alternators are typically grossly undersized for the work they are expected to do. On the flip side, automotive alternators are typically grossly oversized for the work they are expected to do. As an example the stock alternator in my truck is a 150A Denso hairpin wound unit that’s charging a single G24 starting battery. With every device on max the most I have measured for alternator loads is about 28A. That same alternator, charging a 600Ah house bank, would be at maximum output for close to two hours straight. Most owners of marine engines would kill for a 150A rated alternator instead of the grossly undersized 35A-80A alternator many marine diesels are shipped with.

LiFePO4 Alternator Sizing – If you intend to feed a LiFePO4 battery bank with a ProBatt Ultra, and many do, then Sterling’s suggestion of 30% over-sized, for the alternator, we find to be rather inadequate. We recommend at least double the alternator rating, or larger for the B2B charger. So, if you want to use a 30A B2B on LiFePO4 then you would need an alternator rated at a bare minimum of 60A but preferably one sized for 80A would be much better. Each engine bay, and its heat characteristics, will be different, so predicting how much larger is impossible to really say. In our experiments with stock alternators we find double the B2B input rating for the alternator is a bare minimum.

The best scenario with LiFePO4 is to upgrade your alternator before using a Sterling B2B to feed your LiFePO4 bank.

Shore Charger Sizing – Like the alternator, consideration needs to be given to the demand placed on it by the Pro Batt Ultra. Can the charge source handle it? If the charger can run at 100% of its output rating, and do so continuously, and not all chargers can do this, there is little need to over-size by more than 30%. If however, like some AC chargers, it will limit output if it gets too hot you may want to consider upping it to 40% – 50% larger than the B2B input rating. Again, if feeding LiFePO4, this will need even more examination as demand on the Pro Batt Ultra will be near 100% during the vast majority of the LiFePO4 charge cycle.

Alternative Energy Charging – This will be entirely up to you the owner as to how you choose to use the Pro Batt Ultra. With smaller arrays we generally advise ignition excite, it charges start or bow bank when the engine runs, but if you have a large array, voltage excitation can certainly work.

Just try to ensure your charge sources can exceed the demand placed on the B2B by the target bank. In situations where the B2B is charging only a start battery, this is not going to be a big deal, start batteries require very little charging hence little demand on the source bank charger, but as the target bank requires more current, such as a bow-thruster bank or LiFePO4 it can cause B2B on/off cycling so charge source sizing becomes more critical.

Ignition Excitation

For some situations, such as LiFePo4, or a low current PV system, an owner may want the B2B to run when the engine is turned on, even if the input voltage is below the “automatic” turn on point of 13.2V. This is called “ignition excitation” or “key-on excite“. If ignition excite is used the unit can boot up and start charging a target bank with input voltages as low as 10V. The image below shows where the +12V ignition feed would be wired to. To use “Ignition Excitation” all that is required is one wire from the run position of the engine switch.

In this image we can see the ignition terminal of the B2B connected to the “run” position of the engines key switch. When the engine is fired up, there is a brief delay, and then the Pro Batt Ultra will boot up and begin charging the target battery.

Voltage Excitation / Activation

The Pro Batt Ultra (green stripe models) comes out of the box ready to be used in automatic voltage activation mode. By not using the ignition terminal the unit will only turn on once voltage has attained the turn-on voltage of 13.2V, and a short delay timer clock has been run out. The timer delay is to prevent on/off cycling as the bank approaches the voltage turn-on level. The on voltage and cut off voltage can be adjusted up or down but there will always be a 0.2V spread between the ON & OFF points. An adjustable turn-on voltage can be handy when dealing with a LiFePo4 house battery, that may be the “source bank”, and will have a significantly higher resting voltage than lead acid batteries do. In this case increasing the automatic voltage activation point to 13.5V – 13.6V will mean the B2B only boots when the LiFePo4 battery is actually being charged, but don’t forget that the OFF voltage is always 0.2V lower than the ON voltage.

For example; ON = 13.2V and OFF = 13.0V   or   ON = 13.6V and OFF = 13.4V

What about quiescent current draw?

The nice thing about the Pro Batt Ultra is that it automatically puts itself to sleep when input voltage is below the TURN OFF voltage set point (13.0V as it ships). If you fit a remote display the remote also goes to sleep. The quiescent draw or parasitic load that’s placed on the source battery, when the unit is sleeping, is just 1mA! 1mA = 0.001A. In an entire week asleep on standby the unit uses just 0.168 Ah’s. Pretty amazing really.

Alternative Uses for the ProBatt Ultra – LiFePO4

With LiFePO4 drop-in batteries now being heavily marketed, and prices falling to an acceptable level for many boaters, there are issues that can arise that need to be addressed before you can simply “drop them in“..  These issues involve “drop-in” type LiFePO4 batteries that feature a 100% sealed non-communicable internal  BMS (battery management system). The problem is not how the BMS manages the battery, it is in its ability to disconnect the battery from the vessel & charge sources. With most drop-in LFP batteries this can happen without any advanced warning.

A LiFePO4 drop-in batteries internal BMS can disconnect for the following reasons:

• Cell Over Voltage
• Cell Under Voltage
• Cell Temperature
• BMS Temperature
• BMS Current Limits Exceeded

If there is a bad cell, temperature too high, too much charge current, a glitch in the charging voltage settings or a cell imbalance issue creating an over-voltage condition, the battery will physically disconnect itself from the vessel. Most drop-in LiFePO4 batteries can disconnect themselves with no advanced warning to the vessel occupants. This is called a load disconnect or load dump.

A load disconnect or load dump is something a lead acid battery can’t physically do on its own, so this, by definition makes “drop-in” LFP batteries not so “drop-in” because we now need a ways to ensure our alternator or inverter/charger is not suffering load dumps. Of course you don’t need to take out word for it, so how about Balmar, the worlds largest specialty marine performance alternator and regulator manufacturer.

Sure, many an owner has moved a battery switch with the alternator charging and had the destroyed alternator to show for it but the battery did not do this without warning, and the owner made a simple, and often fatal to the alternator, mistake. If a BMS disconnect / load-dump occurs, when charging with an alternator, or even a large transformer based inverter/charger, the resulting *voltage transient,  can damage the charge source and also what ever is connected to the DC bus/system such as sensitive marine electronics.

*Voltage Transient – What occurs when a charge source such as an alternator is suddenly disconnected from the load (battery). The current now has nowhere to go sending the voltage through the roof. When the load (battery) is suddenly disconnected the voltage skyrockets to damaging levels in milliseconds.

During normal operation the alternator operates normally: (most drop-in batteries have the BMS disconnect on the negative side of the battery)

In a fault condition this is what can happen to the alternator:

What a load dump can look like:

How does the Sterling ProBatt Ultra play into this?

The unique aspects of the ProBatt Ultra are in its ability to:

1.  Have a charge profile that is suitable for LiFePO4 (many lead acid charge sources are not ideally suited for LFP)
2. Can withstand a load dump

This image below is why, when discussing the ProBatt Ultra, I prefer to use the terms SOURCE BANK and TARGET BANK. As can be seen we have reversed the way we would typically use the ProBatt Ultra in a lead acid installation and now the start battery is our  source bank and the ProBatt Ultra feeds the LiFePo4 bank or target bank.

“But RC a BB1260 is not enough charge current for my LiFePO4 system?”

Not a problem, simply parallel two or more Pro Batt Ultras together, providing your input charge sources are 30% larger or more, and you can now charge at significantly higher amperage.

While the ProBatt Ultra has been designed to withstand a load dump, other items on-board your vessel, connected to the loads bus, may not be. This is why we recommend a Sterling Alternator Protection Device for every vessel or RV etc. that has drop-in LFP batteries. The Alternator Protection Device clamps the transient to a safe level. We have tested these in our shop, on our alternator test bench, to 130A and not been able to kill one. Installation is very simple & straightforward two wire connection done close to the alternator B+ & B- terminals as shown below:
If you’re installing LFP drop-in batteries a Sterling Power Alternator Protection device is a must-have item: Purchase an Alternator Protection Device

Remote Display

Like any charge management device they are often installed where you can’t see them, and don’t know what is really going on. The optional BBURC is the remote display for the Pro Batt Ultra. It displays charge stage, input voltage, output voltage, unit temperature and battery temperature. It can also be set to alarm a user of a fault condition.

The words remote displayare meaningful because the BBURC is, unfortunately, not for programming the unit. Sterling Power keeps programming at the B2B charger so folks can’t fiddle with the remote and change settings. Little kids love to push buttons. Programming via the remote would be nice but I do fully understand the hesitation. Perhaps in the future there will be a lock-out on the remote to stop roaming fingers from changing settings?

Pro Batt Ultra Likes & Dislikes

No product is 100% perfect and we won’t pretend the Pro Batt Ultra is, but it is quite good and certainly a “best in class” product. Here at Compass Marine Inc. we are big fans of the Pro Batt Ultra because it can do things no other charge management device can.

Likes:

• Dedicated Voltage Sensing
• Adjustable Absorption Duration
• Forced Float Option
• Optional Remote Display
• 1 mA Parasitic Draw When in Sleep Mode
• Can Equalize
• True Fully Independent Multi-Stage Charging Output
• Buck or Boost
• 12V & 24V Mixed Voltage Models
• Compact Size for the Amperage
• Temp Sensor Included
• Can Withstand a Load Dump
• Ignition Excite Option
• Fully Custom Programmable
• Easy to Install
• Best in Class Product
• Pricing is Very Competitive
• Good for Drop-In LiFePo4 Charging
• 2 Year Warranty (many other DC to DC chargers are 90 Days)

Dislikes:

• Owners Manual
• Programming is a Bit Kludgy
• Terminal Strip Orientation for Temp/V-Sense/BMS is Awkwardly Located
• Fan Noise (only when working hard)
• Programming Buttons Vary in Location By Model

Overall the Pro Batt Ultra is a very unique product that no other company even comes close to. The Pro Batt Ultra is a product we are proud to offer to our readers in the MarineHowTo.com Web Store. Please remember the web store at MHT supports this site and keeps it FREE!

BB1230 – 12V 30A Input to 12V Output

BB1260 – 12V 60A Input 12V Output

BB122470 – 12V 70A Input to 24V 35A Output

BB242435 – 24V 35A Input to 24V Output

BB241235 – 24V 35A Input to 12V 70A Output

BB123670 – 12V 70A Input to 36V 23A Output

BBURC – Remote Display for Pro Batt Ultra

Happy boating!

How we Tested the New Balmar SG200 Self Learning Battery Monitor

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The Balmar SG200 is a revolutionary new battery monitor in that its feature set, capabilities and algorithms are a brand new concept in battery monitoring.

The Balmar SG200 is a self-learning battery monitor which was 100% developed in-house by CDI/Balmar. Compass Marine Inc. / MarineHowTo.com worked quite closely with CDI/Balmar, along with other Balmar dealers, to identify what we wanted to see in a fresh new battery monitor. One thing we have grown to appreciate about CDI/Balmar is their willingness to identify what their dealers see as credible needs before pursuing a project.

While every feature we wanted to see, in a battery monitor, did not make it into the SG200, what we do have is a revolutionary new self-learning battery monitor that is flexible, remarkably accurate and incorporates a brand new SoH or State of Health calculation. SoH allows you to know where your bank stands in relation to the programmed or rated Ah capacity and has been previously non-existent in traditional Ah counters.

What is SoH?

SoH is a new feature in the SG200 that compares your banks current state of health to its “as new” factory 20-hour Ah capacity rating.

By industry standards batteries are considered dead when they can no longer deliver at least 80% of their factory rated Ah capacity. While 80% or lower does not mean they are “actually dead” it is where the battery industry sets the low safe level for continued use of deep-cycling batteries.

For setting up the SG200, let’s assume you have a 100Ah rated battery. You would simply program 100Ah into the SG200, regardless of the batteries age or current condition. Over time the *SoH will hone in and find your “percentage of new” state of health of the battery or bank. If the screen reads 77% SoH, after it has had ample time to learn the bank, then this would be an indication that the batteries are nearing end of life and replacements should be on the horizon.

*SoH is a function that only works with banks that are actively deep-cycled. In other words if you purchase an extra shunt for a bow or start bank don’t expect an SoH indication as the SoH feature is specifically engineered for banks that are cycled eg; house banks.

If you’re a coastal cruiser then this number may not be all that alarming but if you venture across the ponds you’ll want to give your bank much more serious replacement consideration when you start getting into the 70’s as a percentage of new.

Development

Like all good things the SG200 did not just happen over-night. All told, it took nearly 4 years to get from ideas on paper to an Alpha level product for testing. Here at Compass Marine Inc. we’ve conducted nearly an entire years worth of testing the SG200. It’s actually still on-going every time we come up with a new way to possibly trip it up or we come across a battery we believe can trip it up. Like most products the SG200 did not come out of the lab “prime-time” ready and a number of software tweaks were made along the way before the finished product began shipping. The engineers at Balmar were tremendous to work with and they responded quickly. While lab testing can’t always predict every single real-wold situation it can be used to develop a platform to start from.  Add in a learning algorithm, and the ability to update firmware for future proofing, and you’ve got a very simple to use product.

SoC, SoH, Amperage & Minutes Left (at current load)

Recently, while up in Maine for a boat show, Chris Witzgall, Balmar’s Product Manager, stopped by our shop to get an idea of how we tested the SG200. Knowing Chris is far better than us with a video camera, we decided to take a different approach to our normal long diatribe of words and photos. We hope this video sums up & conveys how we tested the SG200 and why we were so interested to see yet another battery monitor hit the market.

What we like about the Balmar SG200:

• Multiple shunts can be used with one display to monitor multiple on-board battery banks
• The smarts or computer chip of the SG200 are housed inside the newly designed “Smart Shunt“
• SoH (State of Health) calculation lets you know when your bank is no-longer in a healthy state
• SoC accuracy is quite good within half a dozen deep cycles and continues to get more accurate as time goes on
• Self-Learning means no more cumbersome programming
• Displays – SoC, SoH, Charge/Discharge Current, History, Faults & Alerts
• Supports battery banks up to 1300Ah
• Bluetooth capability via optional Bluetooth gateway
• Firmware changes can be updated via Bluetooth
• Supports Flooded Lead Acid, AGM, TPPL AGM, Carbon Foam AGM, GEL & *LiFePO4
• Supports banks of 12V to 48V
• SoC accuracy as good as 97% in just a few cycles
• Auto-Calibrating
• Remains accurate even as a battery ages
• Less money than the SoC only Smartgauge
• Our customers want simple, not complex, and the SG200 is simple, easy and accurate

*LiFePO4 – The SG200 may not work with certain “drop-in” Chinese LiFePO4 batteries. The SG200 has been tested with Lithionics, Battle Born, Relion, Mastervolt and numerous DIY built batteries with BMS protection operating on the positive bus.

What about Installation?

While the SG200 is a shunt based device, once you understand where the shunt needs to be, as close to battery negative as possible, and that wires that by-pass the shunt (sneaker wires) are not allowed, the installation is very straightforward.

The general installation is simple:

#1 Create a short negative jumper wire to go between the bank negative terminal and the battery side of the SmartShunt

#2 Wire all negative wires on the vessel to the “Cable” or “Load” side of the SmartShunt. Adding a heavy duty busbar can help with this

#3 Mount the display. It fits into a 2 1/16″ hole

#4 Run the SmartLink Cable then install the Deutsch terminal on the end and plug it into the display & SmartShunt

#5 Connect the orange wires to their respective banks (if applicable) and fuse within 7″ of battery positive.

#6 Double check that you have NO DC NEGATIVE WIRES ON THE BATTERY SIDE OF THE SHUNT!

#7 Pull the fuse from the red power + wire and connect it to the banks positive terminal.

#8 Reinstall the fuse and when the SG200 boots up program it with your banks information.

When wiring the Balmar SG200’s SmartShunt you may want to purchase a heavy duty busbar, as shown below, to collect all the vessels DC negatives.

Patience is a Virtue:

TIP: Once your SG200 is installed & programmed please be patient. The SG200 requires your bank to be deeply-cycled quite a few times in order for SoC and SoH to hone in. The deeper these cycles are, the faster the SG200 can learn the bank. Don’t be afraid to take your lead acid bank to 11.7V, if you want to speed up the learning process, just be sure you can recharge to 100% on the next cycle. Shallow cycling will just prolong the time it takes for the SG200 to “learn” bank behavior such as SoH.

Quote: “Rod, I have had my new SG200 connected for almost four weeks and am still getting three dashes for SoH? We have not been able to leave the dock yet but was hoping to know my banks condition before we do?”

***The SG200 can’t learn SoH while tied to a dock charging 24/7***

The SG200 also cannot determine SoH while not charging and resting. To test this, we connected a lead acid battery to the SG200 and let it sit for two and a half months, with no charging or discharging, other than the SG200’s connection to the battery. At the end of 2.5 months the SG200 was still showing three dashes — for SoH. Bottom line? The SG200 is smart enough to know whether you’re cycling or not. The good news is that the SoC prediction, at the end of 2.5 months, was accurate to within 3%, while just sitting there.

SoH Behavior:

At first the SG200 will show three dashes – – – for SoH. It will continue to do this until enough cycles have been completed, and they are deep enough cycles. You’ll want to discharge to at least 50% SoC. Once the three dashes disappear it will start to show a preliminary SoH. If your boat is dockside for a while SoH won’t begin to display until the bank starts being actively cycled. Unlike SoC, which responds more rapidly, SoH is not intended for rapid updating and really needs to learn your banks behavior. Expect upwards of a dozen or more deep-cycles for SoH to be accurate. Be patient!

Insider Guidance:

Please do not make the mistake of comparing the SG200 to a traditional Ah counter. They are not the same at all and not even close to being the in the same category ease of use wise. The SG200 is using multiple technologies to track the bank and doing so in a multiple cross-check fashion. The SG200 can measure and cross-check; battery impedance, internally stored battery behavioral models, voltage – measured many thousands of times per second, coulomb-counting, amperage/load, time *etc. and a self-learning algorithm to bring it all together.

*Etc. – There are other measurements & trade secrets going on inside the SG200 that we cannot publish.

The unique aspect of the SG200 is that each of these data measurements is cross-checked and is compared to the others so that no single measurement can control or skew the data. The SG200 can track both SoH and SoC and to do so very accurately without any cumbersome programming or manual re-sync being necessary.

The SG200 is the most accurate battery monitor for SoC & SoH we’ve tested here at Compass Marine Inc..

As I sit here typing this we have a Trojan SCS-225 130Ah flooded deep cycle battery on the test bench. It recently tested at 99.4Ah or 76.4% SoH. As can be seen the SG200 is reading 76% SoH. It honed in this accurately in just 10 deep cycles. This is about as perfect a prediction of SoH and you can get without an expensive or time consuming 20 hour test. This is rather amazing performance.

SG200 Do’s & Don’ts:

• Do mount the Smartshunt as close to battery banks negative terminal as possible – less than 12″ is preferred
• Do use the largest gauge wire you can between the Smartshunt and battery negative terminal
• Do coat the shunt bolts or nuts with an anti-thread galling compound such as Tef-Gel. They are SS.
• Do use crimping tools that result in the lowest resistance for any wire terminations
• Do aim for the lowest possible voltage drop in your bank & shunt wiring.
• Do connect the red fused wire directly to the battery banks positive terminal *only.
• Do install the fuse for the red wire as the absolute last item installed.
• Do wire parallel or series/parallel bank for optimal intrabank balance.
• Do be patient. The Sg200 can’t work miracles, it needs to learn your bank during deep-cycling use.
• Do cycle deeply on the first few cycles. The deeper you go the faster the SG200 will learn your bank
• Do set it and forget it.
• Do not keep changing settings hoping for it to speed the learning process, all you’re doing is slowing it down.
• Do not depower or disconnect the SG200 from the battery, unless during winter storage.

*For LiFePO4 this decision will need to be weighed by the owner as to place it on the load side of a BMS switch or not. Drop-In LFP you have no choice in this matter. The SG200 will perform best with a direct red fused wire connection to the battery banks positive terminal.

Before you consider an Ah counting battery monitor, one that requires copious amount of human interaction/programming, to keep them accurately tracking the battery, consider the Balmar SG200 and let it do the work for you.

Good luck and happy boating!

Making Sense of the ACR

WARNING: The ACR’s in this article are not for use with LiFePO4 Batteries!

What is an ACR?

An ACR is nothing more than a fully automatic, voltage triggered, BOTH/PARALLEL switch that closes when charging voltage is present and opens when charge voltage is no longer present.

You read that correctly, in its simplest form, all an ACR really does is parallel batteries when charging is present and un-parallel batteries when there is no charging present. It does this automatically with no human forgetfulness.

In days of old a boat owner had to use the battery switch to route/direct charging to the bank or banks they desired to charge. The most ubiquitous of these methods was simply switching to the BOTH/ALL or 1+2 setting on a 1/BOTH/2 battery switch. This was all well and good, charging in parallel, so long as the motor was running. However, when the owner stopped the boat the switch was often forgotten about and left in the PARALLEL position thus draining both batteries while on the hook.

Many a boater has succumbed to two dead banks due to what we refer to as HEF (Human Error Factor). Back in the early 90’s the first of the voltage sensing relays were hitting the market, thus no longer requiring the owner to do anything to the battery switch in order to charge both battery banks. Unlike a diode type isolator, which causes an approximate 0.6V volt drop to the batteries being charged, the combiner/VSR’s were simple voltage triggered paralleling switches and both batteries could be charged without human intervention or the voltage drop associated with diode type isolators.

The Blue Sea Systems ACR’s (automatic charging relays) are one of the most common charge management devices in existence today. In a conversation with Wayne K. of Blue Sea Systems, a number of years ago, he suggested that over 500,000 ACR’s had been sold world wide. Wayne has been retired now, for at least a few years, and that number is now likely much larger. Blue Sea Systems is not the only manufacturer of “Combiner/VSR’s” and today the competition is actually quite wide spread including; Yandina, Sterling Power, Victron, BEP and many, more. Even Smartgauge makes a VSR and the Balmar Duo Charge can be wired to work as a simple VSR. This article deals specifically with the Blue Sea Systems ACR, because they are easily the number one seller in this class of CMD’s. Most VSR’s operate similarly but with varying voltage triggers or delays.

Definitions used in this article:

Charge Management Devices (CMD’s): Devices used to route or direct charging sources to a targeted battery or battery bank. They include ACR/VSR/Combiners, DC to DC buck or boots chargers, diode type battery isolators, DC to DC buck type chargers & DC to DC current limited voltage following devices.

Automatic Charging Relay (ACR): A Blue Sea Systems trade name for an electronic voltage triggered paralleling relay

Voltage Sensing Relay (VSR): A generic term for an electronic voltage triggered paralleling relay

Combiner: Another generic term for an electronic voltage triggered paralleling relay

The term ACR is a trademarked term by Blue Sea Systems for their version of a VSR or voltage sensing relay. The class as a whole is know by many names such as VSR’s, ACR’s, Combiners, Parallel Combiners etc. and they all do just about the same thing.

Despite the gross simplicity of the Blue Sea Systems ACR these little units are fraught with myth and lore. Let’s take a look at some of the myth & lore that are often incorrectly assumed;

ACR Myth & Lore:

1- “An ACR charges the start battery first then isolates it and charges the house” = FALSE

2- “An ACR gives priority charging to the start battery” = FALSE

3- “An ACR will over charge a start battery” = FALSE

4- “An ACR can’t be used with mixed chemistries” = PARTIALLY FALSE

5- “You can’t charge the house bank first or the start battery will never get charged” = FALSE

6- “Blue Sea says to wire charging to the start battery only.” = FALSE

7- “With a smart battery charger you must wire an ACR disable switch into the negative lead of the ACR” = MOSTLY FALSE

8- “When the ACR combines batteries the massive in-rush current can blow up a battery.“ = FALSE

9- “An ACR will allow the start battery to drain into the house battery and leave it depleted.” = FALSE

There are many, many more but, you get the point. Hopefully this article can show you why the above myth & lore are just that.

What is a Relay?

A relay is the control device used inside a combiner, VSR or ACR. It is nothing more than an electronic switch that is closed or opened using a relay coil. By energizing or de-energizing the coil the relay can change positions from OPEN to CLOSED or CLOSED to OPEN.

In this image we are looking at the guts of a combiner/VSR that was 7 years old. It had somewhere around 12,000 hours of parallel combined use on a world cruising boat with solar, wind, alternator and genset charging. As can be seen the contacts are still in perfect condition even after 7 straight years of 24/7/365 world cruiser live-aboard life. Despite these units not being sealed to anywhere near the level of the Blue Sea Systems ACR, the Blue Sea Systems ACR’s are fully epoxy potted, this relay is in superb condition.

What about VSR/ACR/Combiner reliability?

As a class these devices are one of the most reliable devices we’ve seen in the marine market. In fact I can’t recall a single Blue Sea Systems ACR, that we’ve seen, actually fail. This particular VSR, a Yandina, carries an unconditional lifetime guarantee. You can’t guarantee a product like this for life if they are not reliable. We actually see more manually operated battery switches go bad than we do Combiner/VSR/ACR’s. Some ACR’s, such as the Blue Sea Systems 7622 ML-ACR  can be used as a manually operated parallel battery switch and a fully automatic ACR.

Inside a VSR/Combiner:

Contacts: We can see the natural state of the VSR and that is with the contacts normally open or what is referred to as “NO”. A relay with a natural resting state of closed would be called an “NC” relay. If a NO relay loses power it isolates or un-parallels the batteries. When the contacts are closed the batteries are in parallel.

Batt 1 & Batt 2: These heavy duty plated copper buses are directly connected to the Battery 1 and Battery 2 Terminals outside the unit.

Voltage Control Logic Board: This is the smarts of the combiner/VSR. This logic board simply measures the voltage at both Batt 1 and Batt 2 terminals and then tells the coil when to energize or de-energize to close or open the relay. Good quality combiners/VSR/ACR’s also have combine/un-combine delay logic and over or under voltage lockouts built in.

Relay Coil: The relay coil is what causes the contacts to move from open to closed or from closed to open. It is controlled by the logic board. Energizing this coil closed the relay and places the batteries in parallel. De-energizing the coil allows the relay to open and un-parallel the batteries.

ACR Parameters for Combine/Closed/Parallel

First we need to understand where to place/install an ACR. Placement matters. This image is intentionally over-simplified to show relay closed parameters and relay installation wiring and location. If you notice there are no battery switches, chargers, alternators etc. shown in this drawing. This is done purposely. Despite Blue Sea Systems heavily marketing their Add A Battery Kit (7650) an ACR or other combiner/VSR is completely independent of any battery switches. You do not need to purchase an additional battery switch to make an ACR work!

Where You Should Not Install an ACR:
An ACR does not get wired between battery chargers, solar, alternators, wind  etc.. Don’t laugh, we have seen this done. As an example we had a customer wire the alternator output to one side of the ACR and the other side to the start battery and house battery with both house and start bank positive lugs stacked onto the “A” terminal. By placing the start and house battery positive wires on terminal “A” it meant the start and house banks were now hard wired in permanent parallel. This was oops #1.

For oops #2 the owner wound up blowing the diodes in his alternator twice before calling us. With the relay open the alternator output had nowhere to go and the voltage, almost instantaneously, surpassed the 16V over-voltage threshold and the ACR entered “over-voltage lock out“. With the ACR locked open alternator voltage kept climbing until the diodes in the alternator were blown. Bottom line? A Blue Sea Systems ACR is never installed directly into a charge devices positive output path.

Where You Should install an ACR:
As can be seen in the image above an ACR is wired between the positive terminals of each battery bank with the only thing in its path being the fuses located within 7″ of each positive battery terminal. These fuses are there to protect the ACR positive wiring from the battery bank should they short to ground.

TECH TIP: If you make the “A” & “B” terminal wires for the ACR the same gauge as the house and start bank wiring eg: 2/0 and 2/0 the ACR can share the house and start bank fuses, if so equipped.  Start banks are not required to have over-current protection but it never hurts.

The above image is how an ACR parallels:

13.0V for 90 Seconds: If either the B or A terminals of the ACR sense 13.0V for more than 90 seconds the ACR will close and parallel the batteries. The green arrow is pointing to the relay being closed and the banks are in parallel.

13.6V for 30 Seconds: If either the B or A terminals of the ACR sense 13.6V for more than 30 seconds the ACR will also close and parallel the batteries. The green arrow is pointing to the relay being closed and the banks are in parallel.

Question: “I thought the ACR only sensed the start battery?”

Answer: The Blue Sea Systems ACR is a bi-sensing relay meaning it can sense/monitor charging or non-charging voltages at both the “A” & “B” terminals in order to parallel the banks or to un-parallel the banks.

ACR Parameters for Un-Combine/Open/Un-Parallel

Just like the logic used for closing the relay Blue Sea Systems also has logic to control when the relay opens.

12.75V for 30 Seconds – If either the “A” or “B” terminal sense a voltage below 12.75V for more than 30 seconds the relay will open/un-parallel the batteries.

12.35V for 10 Seconds – If either the “A” or “B” terminal sense a voltage below 12.35V for more than 10 seconds the relay will open/un-parallel the batteries. IF voltage is trending upwards and attains 12.75V before 10 seconds has elapsed the relay will remain closed. This logic is here to enure a large load will not cause the relay to open when it creates a short duration voltage sag. It is also there to help minimize “relay cycling” which we will discuss later.

Start Isolation – The SI or “Start Isolation” feature is a unique to the Blue Sea Systems line of ACR’s. The start isolation feature momentarily opens or un-parallels both banks when the starter motor is engaged. The SI terminal of the ACR is wired to the momentary “start position” of the engine switch (see above image) or to the starter button. It is never wired to the “run” position. Doing this will keep the relay open indefinitely. Again, we’ve seen this done. When the starter motor is engaged the ACR’s relay opens so any voltage sag is not transferred to the house bank, where low voltage may cause electronics to shut down. For the SI feature to work as intended you need a dedicated starting battery and a dedicated house bank. The SI feature does not work with a 1/BOTH/2 switch where starting and house loads are shared by the same bank.

16.00V Over-Voltage Lockout – Over-voltage lockout is just what it implies. If the sensed voltage at either the “A” or “B” terminal is 16.00V or higher the ACR will lock out and open itself.

9.50V Under-Voltage Lockout – Under-voltage lockout is just what it implies. If the sensed voltage at either the “A” or “B” terminal is 9.50VV or lower the ACR will lock out and open itself. If you’ve drawn one battery too low don’t expect the ACR to combine until the battery gets back above 9.50V. In a case like this simply use your manual battery switch set to Both or your manual emergency parallel switch.

The above has covered myth & lore 1 & 2

#1 “An ACR charges the start battery first then isolates it and charges the house”.

As can be seen above the ACR does not in any way do this it is either in parallel or it is not in parallel. Very simple..

#2 “An ACR gives priority charging to the start battery”

Please understand that even if you feed charging to the start battery first, which is not advised on a cruising boat with disparately sized banks, 30 seconds of charging is not charging, even for a minimally depleted start battery. A battery at 99% SOC is in the worst range of charge efficiency. Despite being minimally depleted it still takes a good bit of time to reach an actual 100% SOC again. Each Ah we deliver to the battery, at a high SOC, is not being stored at 100% or even 50% due to the horrible Coulombic efficiencies at high SOC. The logic delays in the ACR are not there to create “priority charging” for a start battery or house battery they are there to eliminate relay-chatter and to help minimize relay-cycling or on/off/on/off/on/off behavior.

Q: “Why are there two different parallel voltages and delays?”

It is all about depth of discharge and when it is prudent to parallel the batteries. The lower combine voltage is there for a very good reason. It is there so that a deeply discharged bank does not take very long to attain the combine point. The higher combine voltage is there for a bank that’s not been deeply discharged and rises in voltage near instantly.

This all goes back to myth & lore #5 “You can’t charge the house bank first or the start battery will never get combined & charged” 

Let’s put this myth & lore to bed…..

To address the question of the house bank taking a long time to combine with the start battery, we first need to consider a start batteries actual energy usage.

Start battery Energy Use?
A battery used for starting an engine is using very little stored energy to do this job. It is a very short duration but also high amperage. Most engines will use considerably less than 0.5Ah to start. This is due to the cranking duration, loaded starter to unloaded starter, averaging 0.75 seconds to about 1.5 seconds (averages measured over 70+ marine diesel engines using the Midtronics EXP-1000HD). This means your previously full start battery will still be at about 99%+ SOC after you’ve started the engine. A 99% SOC battery does not really require immediate charging or priority charging and has many, many, many more starts left in it before any charging would even become necessary.

In the image above we have a 44HP diesels cranking diagnostics:

Averaged cranking voltage = 12.04V

Averaged cranking Amps = 286A

Loaded to Unloaded Cranking Duration = 0.765 Seconds

Even if we round up the cranking duration to 2 full seconds we are using just 0.17Ah. If we correct for Peukert, due to the high load on the battery, we are looking at a max fudge factor number of about 0.29Ah’s to start this engine.

Experimentation: For the sake of experimentation we cut power to an external voltage regulator then proceeded to start a Yanmar 4Jh forty-six times before finally getting bored.  The battery used was a single Trojan SCS-200 Group 27 “Deep-Cycle” 12V battery. Not once did this group 27 “deep cycle” battery even so much as wince at starting this motor forty-six times, in less than one hour, without any charging what so ever.

The experiment above was only done to illustrate to an employee why we charge house bank first, not the other way around, on cruising boats. When you run the actual numbers, and see how little energy is used to actually start a motor, it becomes much clearer.

Q: “But how long does it take to attain a combine/parallel voltage?”

From 50% DOD/SOC, the max depth of discharge recommended by most lead acid battery manufacturers, it takes a bit less than 2 minutes at a .2C charge rate to attain 13.0V and this experiment was done on a high acceptance AGM battery.

Q: What is .2C?

The term .2C simply means 20% of the battery banks Ah capacity in charge current. Blue Sea Systems knows how simple it is to attain 13.0V, even for a deeply discharged bank, and this is why their ACR’s feature two differing combine/parallel voltage points, one at 13.0V & 90 seconds and one at 13.6V & 30 seconds.

This battery began charging at 50% DOD/SOC when the clock read 12:00. The charge rate was .2C or the bare minimum recommended charge current for this Lifeline AGM battery. As can be seen, after just 2 minutes of charging at 21A, it is already at 13.1V and the ACR can now combine. If your start battery is going to suffer not being charged for two +/- minutes, you have other issues.

Rumor/myth & lore #5 goes something like this: By using a battery combiner, on “high acceptance” AGM batteries, and feeding the alternator or battery chargers charging current directly to the house battery bank first, “it will leave your start battery under charged“ because “it will never get to the combine voltage or will take too long to get there”.

If you are practicing good battery management, and have even the minimum suggested charge current for an AGM or flooded battery, this is really a non-issue. In 2 minutes of charging, at .2C or 20% of Ah capacity from 50% SOC, the AGM battery voltage is already at the parallel/combine level for the Blue Sea Systems ACR. Even at .1C or 10% of Ah capacity the time to attain 13.0V is not very long, just a few minutes more. To get from 13.0V to 14.4V+ does take quite a bit more time but the relay has already combined at 13.0V and both banks are now being charged.

Battery voltage will rise pretty slowly from the low 13’s on but, to get to an ACR’s combine level, is relatively quick and easy, especially if you have your system set up properly. When hearing this rumor we need to also consider that Echo Chargers, Duo Chargers and a number of other DC to DC chargers also turn on at similar voltages and those devices require all charge sources to be fed directly to the house bank. On cruising boats with disparate sized banks Blue Sea Systems recommends feeding charge current to house first, not start, but you have the option to choose start first if you really feel the desire and you don’t with other products such as the Echo Charger, Digital Duo Charger etc….

Correctly Wiring an ACR on a Cruising Boat

While a three wire device, four if you use the SI feature or five if you use the remote LED indicator, seems simple to install, there are some areas that can trip you up. One of the most common blunders we see on cruising boats is leaving the alternator wired to charge the starting battery first.  This is most often the result of the Blue Sea Systems instructions not being very clear. The majority of these are sold for use on boats where the battery banks are nearly identical in size. They are very, very popular on center-console and walk-around fishing boats where the start battery and house batter are nearly identical in size and the motor is started and stopped multiple times per day while fishing and owners don’t want the sounders and plotters to drop out during starting (SI). With both banks nearly the same size feeding the start battery first works pretty well. Because most builders sell boats wired this way, alternator feeding start battery, this is how they are typically wired. In an ideal world the charging would be fed directly to the bank that gets most depleted.

On a cruising boat, with a large house bank and small start or start/reserve bank, the best way to wire an ACR is to have the alternator charge the house bank directly.

“Why is it best to charge the house first?”

There are a number of reasons to do this but the best reason is to ensure the bank that needs the most charging is actually getting it and getting it as efficiently as possible.

#1 With large house banks wiring charging sources to the HOUSE bank means more efficient charging and more optimal voltage sensing for the alternator.

#2 With large house banks, wiring charging sources to the HOUSE bank means less chance of what is called relay-cycling. Please take the time to read the link below. Blue Sea Systems covers relay cycling very well so there is no sense in us repeating it.

Preventing Cycling in Battery Combiners, Voltage Sensitive Relays, and Automatic Charging Relays

#3 By wiring charge sources to the larger HOUSE bank the relay contacts need to pass just a few amps at best in order to charge the start battery. By feeding all charging to START means the relay must be able to handle the full rated current of the alternator and we are utilizing it at max duty cycle. We are also passing the charging current through multiple more terminations and fuses and there will be additional voltage drop.

One part of the instructions that most installers miss is this:

What About Fusing / Over Current Protection?

One topic that comes up rather routinely is ACR fusing/over-current protection. Because the ACR or VSR is connected directly to the battery banks + terminals, or their respective *close-by charge / always on distribution bus, the wires themselves need over current protection. There is some confusion regarding ACR fusing, even among some professionals, that the fuse is intended to protect the ACR, and it is not. The fuse is there to protect the wire as Blue Sea Systems clearly illustrates below. If we are following ABYC standards these fuses should be within 7″ of the banks positive terminals or their bus.

(*Within 7" of the banks + terminal)

Fuse Sizing

One mistake we see all too often is a 120A 7610SI ACR installed with a 120A alternator feeding directly to a start battery and the relay is protected by a 120A fuse. If the house bank is heavily depleted the relay can conceivably pass close to 120A across it for a short period of time or until the alternator heats up and can no longer produce its cold rating. Also keep in mind that many alternators can exceed the cold rating for short periods by as much as 15%. I think you can see why a 120A alternator with a 120A fuse would spell disaster for the fuse especially when fed to the start bank first.

The fusing is there to protect the wire not the ACR, so if you have a 120A alternator the minimum fuse & wire size should be 175A & 1 AWG minimum. Fuses should not be run at 100% of their rating or they will eventually nuisance trip. This is why Blue Sea Systems calls for a 175A fuse for a 120SI ACR when being used with a 120A rated alternator. Of course if you wire it correctly, for a cruising boat, and the alternator feeds the house bank first, the relay will never see 120A across it except during very brief inrush duration’s that are not long enough in duration to trip the fuse.

TECH TIP:

If your house and start banks already have over current protection you can simply use the same size wire for ACR “A” and “B” terminals as the bank is wired with. In other-words you can share those fuses for protecting the A & B ACR wires, provided you use the same size wire. If both banks are already fuse protected this can mean no additional fusing costs for the ACR installation. If you make use of an already fused charge/always on bus, as shown below,  you can just connect the ACR to that bus with the same size wire the banks are already using. In the example below the banks are wired with 2/0 wire and fused at 300A.

The use of a charge / always on bus is certainly a best practice and one more professionals and DIY’s should do more often. A charge/always on bus prevents messy bank wiring & incorrect lug stacking and makes for a neat and tidy installation anyone can easily troubleshoot.

Connecting Other Charging Sources

One of the major benefits of an ACR is that it works with any and ALL CHARGE SOURCES. Because an ACR is triggered by voltage changes it means that its an extremely valuable tool for charge management. Unlike a diode type isolator, that can really *only work with an alternator, the ACR can work with alternators, wind, solar, hydro, fuel cells, and AC chargers.

*Diode Isolators – Diode type isolators do not have a voltage reference on the input stud. By voltage reference I mean if you place your DVM on the input stud of a diode type isolator you will read 0V. This is one of the number one trouble shoot calls we get from folks trying to integrate solar or wind to multiple battery banks using a diode isolator. A diode isolator can’t be used with most charge sources that need to see a DC voltage before booting up. Today most voltage regulation charge sources have a feature that does not allow them to boot into no voltage where a typical “dumb alternator regulator” will. This is a safety feature so you’re not charging into a failed battery. Today there are very few good uses on a boat for a diode type isolator.

The question of other charge sources ,and an ACR, comes up a lot. Due to marketing it can be a bit murky wading through it all. The bottom line, for simplicity & operational sake on a cruising boat, is that you want to wire all your charging sources to the largest bank eg: the house bank. This would include, alternator, AC powered battery chargers, inverter/chargers, solar, wind, hydro or fuel cells. It is critically important to wire low-current charge sources such as solar, wind, hydro, fuel cells or small battery chargers directly to the house bank to prevent relay cycling.

In the image below we can see a cruising boats foundation wiring with a 500Ah AGM HOUSE bank and a 125Ah AGM START/RESERVE bank. As can be seen all charge sources feed the house bank and the ACR parallels in the start bank when 13.0V or 13.6V is attained.

What about twin engine boats?

On twin engine boats one alternator, usually the largest and most capable, can feed the house bank directly and one can directly feed the start bank directly. The addition of an ACR means that both alternators will contribute to the house bank charging during bulk. Without the ACR the start bank alternators full capability is just being wasted by feeding a few amps at best to the start battery. By adding an ACR we can make much more effective use of both alternators and charge the house bank faster.

Myth & Lore #10- “With a smart battery charger you must wire an ACR disable switch into the negative lead of the ACR”

This one can be a bit confusing but all boils down to what is actually inside a “smart-charger“. If your smart charger actually has multiple voltage regulators and multiple power supplies inside it, then a switch in the negative lead can allow the charger to charge each bank with its own fully independent charge profile. The catch here, and why this is MOSTLY FALSE, is because finding a smart charger with two or three fully independent chargers inside one box is about as likely as Hillary Clinton switching parties and becoming a Republican. Follow me for a moment..

What you think you’ve paid for:

What you actually have:

Another way to view most multi-output chargers would be like this:

With this image it becomes more clear how the single voltage regulation and single power supply can be connected to multiple batteries through “isolated outputs”. For this example I drew simple diodes, an electrical one-way check valve, but most chargers these days are using FET’s on the outputs to achieve the same effect. The only purpose of the FET or diodes on each output leg of the charger is to prevent the batteries from back-draining (in parallel with each other) into each other when the charger is turned off. You guessed it all batteries get the exact same charge profile just as they would if you fed charger output #1 to HOUSE and then used an ACR to charge the START battery.

Let’s discuss myth & lore #3: “An ACR will over-charge a start battery”

Please examine the above images and let them hit home. Now ask your self a simple question; How is a “smart charger”, a model that uses one voltage regulator and one power supply and two or three diode or Mosfet (FET) isolated outputs, any different than the BOTH setting on your battery switch or the combined mode of an ACR? If you landed on “its not any different” reach over your shoulder and pat yourself on the back. The diodes or FET’s on the single circuit of a multi-output charger are only there to prevent parallel back-drain when the charger is turned off. An ACR achieves the same exact outcome, preventing back-drain, by opening the relay when no charging is present.

The same guys who walk the docks and profess that an ACR will over-charge a start battery are quite often the same guys professing why you need a smart charger to charge your multiple on-board battery banks. I know this because one of these guys attempted to re–edumacate me on a dock one day, & he used this very argument. The charger on his own boats was a muti-output single power supply single voltage regulation unit. The funny part about this re-edumacation was the start battery on the boat I was working on was 8 years old and had been charged via a Blue Sea Systems ACR for the entire 8 years. It had been charged via multiple charge sources, including a shore charger, solar & alternator. According to the “dockspert” that start battery had been murdered 7 years ago by the ACR yet in the real world it was still going strong at year 8.

It was not worth trying to explain the concept to him, in a short period of time, and besides he’d already made up his mind on the subject. Little do folks realize there is usually no difference between using the multiple-outputs of a battery charger vs. using just one output of the charger and an ACR.. The ACR simply prevents back-drain by opening the relay when there is no charging & the smart charger uses diodes or FET’s to prevent back-drain. Whether you use the isolated outputs of the charger or one leg of it, and an ACR, there is really no difference.

The vast majority of multi-output smart chargers are one charger hiding behind two or three back-feed prevented (diodes or FET) outputs. If you want to charge multiple banks, and you already have an ACR, use the ACR, as it will work with all charge sources. This will save you charger to bank wiring and an extra fuse/s. To get around the multi-output charger and differing bank voltage profile conundrum, a situation where neither the multi-output charger nor the ACR would be a good choice, Sterling Power products offers their Battery Chemistry Module.

Ok back to our dockspert for a moment.

If your single power supply, single voltage regulation smart-charger is not over-charging your start battery, how is it that an ACR would?

Think about it…… Even Blue Sea Systems own “P-Series” chargers are one single voltage regulator and one single power supply. They market the product describing how it can float one bank while charging the other at absorption. While this is certainly a nice selling feature we still have millions of single VR/single power supply multi-output “smart chargers” out there that don’t do this, and yet we don’t have start batteries being routinely over-charged & murdered.

What Blue Sea Systems is actually doing in the P-Series is switching in an additional diode to the start battery output leg. Switching in an extra diode causes a 0.6V drop on the start battery output. It is not a truly independent smart charge profile but rather a 0.6V drop from the absorption voltage & a nice selling feature for sure. To do truly smart-charging, the type most boat owners assume they have, the charger would need multiple voltage regulators and multiple power supplies something very, very few chargers actually have.

Still, if you desire to allow your “smart-charger” to do it’s thing, or you use a Sterling Power Battery Chemistry Module or Blue Sea “P-Series” and feel it does a better job than the ACR, by all means insert a simple ON/OFF switch into the negative lead of the ACR, to disable it, or just flip the switch of the ML-ACR to OFF..

When to Use a VSR/ACR/Combiner

To keep this simple, when charging lead acid batteries, is that it’s all about the appropriate charging voltages. Also we can’t forget that GEL, AGM, TPPL AGM and Flooded Deep Cycle batteries are all lead acid chemistry.

With that in mind;

If both banks can be charged within 0.1V to 0.2V of each other, an ACR is a fine choice

Same Chemistry & Same Charging Voltages = √

Same Chemistry & Very Similar Charge Voltages =  √

*Mixed Chemistry & Same Charging Voltages = √

*Mixed Chemistry & Very Similar Charge Voltages =  √

*Excludes mixing lead acid and Li-Ion batteries

Most lead acid batteries will have a safe voltage range for absorption & float. If we compare a bank of Trojan golf car batteries and a Trojan Group 31 12V battery it’s clear to see they share the same charging voltage range and thus a VSR/ACR/Combiner is a good chocie for this application.

When Not to Use a VSR/ACR/Combiner

If we go back to Myth & Lore #4; “An ACR can’t be used with mixed chemistries”

We describe this as “partially false” and here’s why…

Let’s assume you have a GEL house bank, an excellent deep cycling battery, and a TPPL AGM windlass bank and excellent high current capable windlass or thruster bank. The GEL battery should not be charged at over 14.1V to 14.2V so the primary charging sources, solar, wind, alternator, chargers etc., would all be set up for a maximum of 14.1V to 14.2V. The problem here is that the ideal charging voltage for a TPPL AGM bank is closer to 14.7V. In this case, if charging is set up for 14.1V to 14.2V, we will wind up chronically undercharging the TPPL AGM bank via the ACR.

If we reverse this scenario, and the charging is tailored to the TPPL AGM bank, we will quickly destroy the gel battery by over-charging it.

Same Chemistry & *Differing Charging Voltages = X

Mixed Chemistry & *Differing Charging Voltages = X

*Differing by more than 0.3V

If specified charging voltages are the same or similar then an ACR/VSR/Combiner is a worthy choice. Once we get beyond about a 0.3V difference, it starts to make more sense to move to a DC to DC charger such as a Sterling Power Battery to Battery Charger where we can get a true fully independent smart charge profile.

“But an ACR will Discharge my Start Bank.”

This statement takes us directly to Myth & Lore #9 “An ACR will allow the start battery to drain into the house battery and leave it depleted.”

The fully charged resting voltage of a typical lead acid battery is about 12.72V. At any voltage above this point there is really no usable energy stored when discharging (see image below).

By now I know you are understanding it, but if not, this one is really quite simple. The ACR normally opens/un-parallels at just above or just at the 100% SOC point of a lead acid battery. If either battery bank dips below 12.8V the relay opens within 30 seconds. If it dips to 12.35V, the relay opens in just 10 seconds. The answer to this myth is that it is indeed false that an ACR will allow the start battery to discharge into the house bank. Your start battery cannot discharge into your house bank in 10 or 30 seconds.

The discharge graph below (voltage is the red line) was a typical marine battery undergoing a 20 hour capacity test. The battery was fully charged, equalized and had an open circuit voltage before the discharge test of 12.95V or what we refer to as a “surface charge“, despite having rested for a full 24 hours prior to the test. Because this was a 130Ah rated battery the discharge rate was 6.50A (130Ah / 20 hours = 6.5A discharge rate). At data point #1 the battery was at 12.95V and by data point 2 the battery was already below the open/isolated/un-parallel voltage of the ACR at 12.76V.

You are seeing that correctly, by the time this battery hit 12.76V a paltry 0.002Ah worth of energy had been removed. If the ACR opens at 12.8V how much can we discharge either bank by? This answer is nothing worth even really discussing…

If the relay opens at 12.8V it can’t remove any Ah quantifiable capacity from either bank before the banks are isolated.

This does bring us to another myth we have heard and that is when the banks are combined, in parallel, they can transfer energy between each other. This one is also a pretty simple explanation.

The ACR combines at well above the natural resting voltage of a lead acid battery. Due to this, charge current can only flow in one direction and that is into the battery. At 13.0V or higher current flows is into the battery from the charge source and the charge source would take up both the DC loads and the charging.

The combine point of 13.0V is a charging voltage and when a battery is charging it can not also be discharging. It can only be discharging when voltage is below charging level. Very, very simple.

The final point we should discuss is myth & lore #8;

“When the ACR combines batteries the massive in-rush current can blow up a battery.”

The easiest way to answer this question was to create a scenario on the test bench that could show these “massive” currents, currents so huge they can blow up a battery. (sigh)

The math could easily be calculated to show why this is not a concern but, it is often easiest to physically see it in action. In the video below we created and tested for the scenario that created the highest in-rush current we could create. The term in-rush, as related to this example, just means the absolute peak current measured over a very *brief time period,  between banks, at the widest voltage spread.

*The Fluke 376 captures current transients at 0.1 second or one tenth of one second.

The point where the banks are combined, and voltage spread is widest, is the point where the most current transfer is created. This in-rush lasts less than .2 seconds and current transfer, between banks, literally nose dives very rapidly as the bank voltages close in on each other and attain parity.

We created this scenario based on a very popular 315Ah AGM house bank (3 G-31’s) with an AGM starting battery. In order to try and capture the most in-rush we could, an Odyssey Thin Plate Pure Lead AGM, or TPPL AGM, was chosen as the start battery. The Odyssey PC2150M is a battery that can deliver over 5000A of current into a dead short, 2150A of cranking current at 77F and 1150A of cranking current at 0F. The 172A peak current it delivered to the house bank, for about .2 seconds, is literal child’s play. The test delivered the maximum recorded in-rush current at about 30% state of charge or a 70% depth of discharge. This is a depth of discharge you should not be routinely seeing with typical AGM batteries. Interestingly enough when we discharged the large house bank to 80% or 90% DOD the maximum in-rush was actually lower than it was at about 70% DOD. We chose to show the maximum in-rush we could create.

If we have 315Ah’s of AGM batteries, and we play pretend fairy-tale stories and assume the 172A in-rush could last for even 30 seconds (it can’t physically do this) this equals a charge rate of about 0.54C or just 54% of Ah capacity. In the Practical Sailor PSOC testing all the AGM batteries were actually charged, not an in-rush, at .46C (46% of Ah capacity) and the batteries barely even got warm to the touch. Of course this extremely short in-rush is not a “charging current” it’s a fraction of a second peak-transient current and is in no way dangerous to your battery bank. Yes, myth & lore #8 is indeed false and there are no “dangerous” in-rush currents created when the banks parallel with each other.

Another example of why this is not dangerous, Lifeline battery states their 100A AGM battery can handle 500A of in-rush charge current with ease. This equates to a charge rate of 5C or 5 times Ah capacity. As you’ll see below the ACR switching closed could only transfer 54% of Ah capacity in this test for a very brief 0.2 second transient.

In this video you will also see the effects of relay cycling and why hooking up a cruising bank incorrectly can create this phenomenon..

Choosing an ACR

Blue Sea Systems offers two distinct types of ACR models, the basic fully automated SI-ACR’s and the larger, manual or fully automated ML-ACR’s. Both charging relays feature fully potted electronics, heavy duty 3/8″ studs and the ability to charge two banks.

ML-ACR – The ML-ACR is a step up from the basic SI-ACR, and also costs a bit more. For a bit more money you get a lot more in features and current carrying capability and it can handle as much as 500A continuously. The ML-ACR also allows for manual paralleling of banks via a dash mounted toggle switch or the yellow knob on top of the ML-ACR. This means the ML-ACR could take the place of your emergency paralleling battery switch and do double duty as both an ACR and an emergency paralleling switch. The 500A continuous rating makes it the ideal product for boosting the available current to a bow bank used for a windlass or a bow thruster. With the flip of the toggle switch it can go from automated ACR charging, which would open on voltage sag, to manually locked in parallel. This means your bow bank, house bank & alternator can now all contribute to your windlass or bow thruster performance and you can rather drastically improve bow thruster or windlass performance. The ML-ACR also features SI or start isolation. Standby draw on the ML-ACR is a scant 13mA or just 0.013A.

SI-ACR – This is the basic fully automated model and is a relatively inexpensive upgrade. The 7610 SI-ACR can handle 120A continuously, has SI (start isolation), fully potted electronics and heavy duty 3/8″ studs. If you don’t need the high amperage or manual paralleling feature of the ML-ACR the SI-ACR is a great value. Standby draw on the SI-ACR is just 15mA or 0.015A.

Today there are lots of options for charging multiple banks, without suffering from voltage drop, and the ACR/VSR/Combiner is just one of them. We stock quite a few charge management devices in the MarineHowTo.com webs store.

MarineHowTo.com – Charge Management Devices

Good luck with your project & happy boating!

Making Sense of Alternator Frame Sizes & Output Ratings

Aftermarket externally regulated higher performance alternators are generally classed into three basic categories – Extra Large Frame, Large Frame or Small Frame.

The differences in case (frame) sizes can be seen here:

Many marine engines, other than some large Cummins, Cats etc., generally ship with what is called a small frame alternator. Small frame alternators run the gamut in terms of build quality and durability but none of them are what could be considered “constant duty“. The only way I know of getting a constant duty small-frame alternator is to remove the internal rectification and rectify remotely. This is what I have done on my own vessel for charging a large LiFePO4 battery bank.

“RC, What does constant duty mean?“

What it means is the small frame alternator you purchased is simply not a “constant duty rating” no matter who’s name is on it. For years and years, with moderately sized banks of deep-cycle flooded batteries, this did not really matter because the batteries came up to voltage pretty quickly and then the alternator caught a break.  Today I have customers with 600Ah plus battery banks on 30 footers. This may seem insane by yesterdays standards but not by today’s standards. The growth & use of computers, tablets, TV’s and other  iToys over the last ten years has been immense. Today it has many of our customers exceeding the daily energy consumption of their DC refrigeration. Not too long ago DC refrigeration was the huge energy hog today, for many, it is computer, tablet and device use.

Small Frame Marketing Hype

The Real World Reality

The cooked alternator you see below was made by manufacturer of the rather brash statement above. It was marketed in what I would consider to be a grossly misleading manner. This alternator was a small frame, single fan unit and we have seen many of them burned up, from being over-worked while not being adequately temp protected.

Burned up alternators like you see below can happen due to a lack of alternator temp sensing/protection and/or a lack of being able to current limit the alternator. Compass Marine Inc. actually builds the identical alternator using the same internal components from the same manufacturer. We go a few steps further however and build the alternator with 400V 75A diodes. The manufacturer of the misleading claim above used only 200V 50A diodes. Despite the ability of our version to deliver significantly more power, and for longer, we would never, ever tell a customer the Compass Marine Inc., CMI-HD125-ER, is a continuous duty unit. That would be pure unadulterated BS.

This one was charging a large AGM bank and was the second identical alternator to suffer the same exact fate. Two separate but identical alternators completely cooked themselves in a matter of months. The pictured alternator was measured at 367F when the owner had noticed his tachometer stopped working. Upon opening the engine bay a thick acrid smoke hit him in the face. The regulator being used on this alternator had no alternator temp sensor and no way to current limit it. The regulator was replaced with a Balmar MC-612, plus an alternator temp sensor, and current limiting or “Amp Manager” was used. The third identical alternator is still running to this day, 9 years later.

There is no small case alternator we know of that can run continuously at full output.

Anyone telling you otherwise is simply a bovine dung artist

“But RC I bought an XXXXXX brand alternator and it has a hot rating?“

Please let’s not misconstrue the difference between a cold rating & hot rating and a “constant duty” rating. A hot rating and a constant duty rating have no relation to each other at all. In the industry alternators are tested to ISO 8854 or SAE J56. These testing standards help standardize output ratings at a certain RPM, temp and test voltage.

Alternators tested to J56 are simply rated like this:

Test Temp = 23ºC  ± 5ºC

Test RPM = 6000

Test Voltage = 13.5V

Unfortunately this industry standardized testing is not designed nor intended to see how long the alternator can run at full output into a large bank of deeply discharged batteries. In other words, an alternators output rating is rated cold (73ºF to 83ºF) at 6000 shaft RPM and 13.5V. Simple stuff.  While some marine alternator manufacturers, such as Balmar, provide both a cold (79ºF) and a hot rating (194ºF) this hot rating is still not a constant duty rating. The hot rating is simply telling you the expected drop in max achievable output, as the copper in the alternator heats up to 194ºF. A cool alternator simply produces more peak output than one at near 200ºF.

A “Hot Rating” is not a Continuous Output Rating

Why don’t manufacturers supply a constant duty rating? The reason is pretty simple, it’s because every application and engine space is different and providing a continuous rating is nearly impossible to apply across each installation scenario. Below are three examples of measured engine room temps to illustrate why this is not done with small-frame alternators:

Boat #1 Engine Room Temp = 162.4ºF

Boat #2 Engine Room Temp = 171.1ºF

Boat #3 Engine Room Temp = 132.5ºF

The alternator on boat #3 is going to have a much better chance of staying in a safe operating temp range than the Boat #1 or Boat #2.

A cold and a hot rating are simply the short term outputs at 6000 RPM and the rated temp. If your application requires an alternator capable of prolonged continuous duty output there are options.

1. Choose a *higher output small frame alternator and use Balmar’s Belt Load Manager feature to limit maximum output = Easiest / Least Expensive $
2. Choose a small frame alternator but remove the internal rectifier and rectify remotely = Difficult to DIY / $$$$
3. Install a large frame alternator designed for continuous duty use = Difficult to DIY / $$$$$$

* When case size remains the same, the increased output, when choosing a higher output unit is not linear. In other words choosing the 150A model that is also available in a 75A model does not net you double the continuous safe output.

What About Hairpin Small Frame Alternators?

The term hairpin refers to a stator design invented by the Japanese manufacturer Denso. The design places a lot of copper into a small space by using square magnet wire that can nest more tightly. Balmar uses this technology in its AT-165 and AT-200 series alternators. 

Where the hairpin design alternators shine is in better efficiency, which means less heat developed, and for applications where we have a slow turning engine or a need for a high percentage of full output at a low RPM such as charging at anchor or low RPM motor sailing.The hairpin design can produce a lot of current at low RPM.

The AT series really shines for low RPM charging.  However, please don’t be confused into thinking you can run these alternators full-bore into a 1600Ah bank without some sort of temp protection strategy such as Belt Load Manger and an alternator temp sensor. They are still small frame alternators.

In the foreground is a Balmar hairpin stator and behind it a standard wound stator. You can see why the hairpin design can deliver so much current at low RPM when compared to a standard designed stator.

Alternator Mount Styles

For marine applications there are four basic mount styles that make up most of the installations;

1″ Foot – Westerbeke, Volvo, Perkis, Cat etc.

2″ Foot – Perkins, Universal Diesel, Vetus, Cummins, Volvo etc.

3.15″ Saddle Mount – Yanmar & some Mitsubishi/Westerbeke engines

J-180 Saddle Mount – Large diesel engines such as Cummins, Detroit, Cat etc.

1″ & 2″ Foot Mounts – For aftermarket use most manufacturers will build  1″ foot alternator that can easily be converted to a 2″ foot with the addition of a spacer or spacer kit. This makes a 1″ foot alternator one of the most versatile in the industry and it has the widest engine fitment range.

3.15″ Saddle Mount – These frames are also commonly known as dual-foot or Hitachi mount alternators. The popularity of the Yanmar marine engines is so vast that it makes sense for aftermarket performance alternator builders to produce a model that specifically fits Yanmar engines. A saddle mount alternator, such as the 3.15″ style, may also be used in many single foot applications, with careful use of spacers. Saddle mount alternators feature a *drift bushing.

J-180 Mount – The J-180 mount is fond on large frame alternators and is very similar in design to the Yanmar saddle mount. The scale and the ID width is approx 4″ between feet and it uses uses a 1/2″ pivot bolt as opposed to a 3/8″ or 10mm bolt. Saddle mount alternators feature a *drift bushing.

IMPORTANT: Not all alternators, with a similar mount style, share the same offsets and this is why careful installation and proper alignment are critical.

Belt & Pulley Choices

No discussion regarding a marine alternator installation would be complete without discussing belt & pulley choices. Until very recently the marine industry has supplied most engines with single or dual v-belts to drive the stock alternators. The use of a single v-belt was marginally suitable when boats had very little DC load or demand but today many boaters have far exceeded the capabilities of a stock 30-60A alternator and have also often exceeded the capabilities of a 3/8″, 1/2″ or even a 5/8″ single v-belt. Some owners, who’ve been overwhelmed with belt-dust, have increased the alternator pulley size to yield more belt to pulley surface area but, this is a Band-Aid solution that results in poor alternator performance due to reductions in alternator RPM.

“Industry Accepted” Recommendations for V-Belts

• 3/8″ V-Belt = 80A
• 1/2″ V-belt = 100A

This guidance can be a truism, to some extent, but it will require;

•   Impeccable Alignment
•  Near 180 degrees of belt wrap
•  Extremely clean pulleys
•  Relatively short bulk charging duration’s
•  A high quality belt

More Realistic Maximum Amperage Recommendation

• Single 3/8″ or 10mm V-Belt = 70A
• Single 1/2″ or 13mm V-Belt = 85A.

Limitations of V-Belts

Lower HP drive capability – When compared to flat style multi-rib belts

Prone to over tightening – Many a boat owner or marine techs have over-tightened a v-belt in an attempt to minimize slippage or belt dust but in the process damaged a water pump or other accessory drive. Over tightening a v-belt does not really aid in less slippage and can actually have an effect that is opposite the assumed outcome.

Excessive frictional heat – This heat can actually damage the alternators front bearing and transfer excess heat into the alternator. Frictional pulley heat can also be exacerbated by the use of cheap stamped steel pulleys (see image below) which tend to expand the V gap as they heat up. This can cause the belt to become loose under load. Using billet machined pulleys can help to minimize this.

Engine choking belt dust – Many v-belts contain abrasive materials such as Kevlar or Aramid fibers. When these abrasive fibers are turned into belt dust it can actually cause damage to engines. Diesels use and need lots of fresh air for the combustion process and that air needs to be free and clear of abrasive contaminates. The idea that a marine diesel does not need an air filter can be an engine damaging old-wives tale. The image below illustrates why a quality air filter on your marine diesel is a good idea.

Typical Marine Pulley Types

Multi-Rib belts, often referred to as “serpentine belts” or flat belts are a more efficient design and can drive considerably more HP without developing the same level of frictional heat. Flat multi-rib belts approach drive efficiencies of 99%+ where a v-belt is nearly 2.5%-3% less efficient. Even with perfect sizing and loading the v-belt is developing more frictional heat.

For owners who desire more amperage capability from their engines, manufacturers such as Balmar/Alt-Mount or Mark Grasser DC Solutions are now offering custom multi-rib pulley kits. These kits bolt onto your existing engine and are a sure fire way to drive more HP with less belt tension and virtually no belt dust. The Balmar / Alt-Mount kits are usually a 10 Groove or a 6 groove design, depending upon the kit, and the Mark Grasser DC Solutions kits utilize an 8 groove pulley design.

These are the most common pulleys for marine engines rated by effectiveness:

Belt Wrap Considerations

When considering an alternator upgrade the desired amperage and the actual belt-wrap of the existing pulley can’t be ignored. Many alternator belts are also used to drive water pumps, as seen here, and this means the belt wrap around the alternator pulley is going to be less than optimal.  Less than optimal belt wrap usually means your single v-belt will not strictly adhere to the industry max capability recommendations of 80A for a 3/8″ belt and 100A for a 1/2″ belt. These recommendations are assuming a near 180 degree wrap around the alternator pulley. This brand new alternator installation is a prime candidate for a serpentine kit.

Pulley Cleanliness

When upgrading your charging capability one of the best things you can do is to ensure your existing crank pulley, as well as your  water-pump pulley surfaces are clean and free of rust or corrosion. Rust and corrosion act like sand paper on your belt/s and create rapid wear, a need for continual adjustment, and excessive belt dust.  To remedy rusty & corroded pulleys a drill and wire wheel, or a Dremel type tool with wire wheel, can be used to clean the pulleys to bright metal. In this image a water-pump pulley gets a cleaning. You’ll be amazed at the difference this one small step can make.

What About Double-V Pulleys?

Double-V pulleys are pretty common and perform far better than a single-V pulley arrangement but they too can be more problematic than a multi-rib pulley system. If your vessel already has a double-v belt pulley system I would recommend using it, unless you desire more than 130A to 140A of alternator charging. Years ago, when industry used lots of v-belts, finding  a *precision matched pair of belts was pretty easy (*Gates terminology), today, not so much. For the set up pictured below, Gates recommended their Aramid reinforced Predator Industrial Series belts but with limited sizing, in the industrial line, and the inability of the Predator series belts to wrap the alternator pulleys small outside diameter properly, the Gates XL Series was the next best choice.

Gates, Dayco and other belt manufacturers claim that today’s manufacturing process has eliminated the need for “matched pairs“. Interestingly enough Gates still offers “precision matched pairs” for industrial applications customers? If there is “no need for this due to manufacturing” then why? Precision Matched Pairs are actually hand measured and matched but sizing is really quite limited when compared to marine application needs. For a high amperage marine application finding a well matched pair can be difficult at best. Your best bet is finding your largest NAPA, or other large automotive or industrial belt distributor, such as Motion Industries, and choosing your belts by:

•  Same Date Code
•  Same Factory
•  Same Lot Number
•  Closely Matched Production Run Numbers

This is a guide to deciphering Gates numbers and matching the belts as closely as possible:

Pulley Width Considerations

Unless you’re using a Balmar 1/2″ wide pulley, be careful to only use a 3/8″ width pulley if you have a 3/8″ wide belt. Balmar specifically machines their 1/2″ pulley, such as the 61-0010,  a bit deeper so that the 1/2″ pulley can be used with a 3/8″ wide belt. Most other 1/2″ wide single-v pulleys are not machined this way. As can be seen here a 3/8″ belt was used on a 1/2″ pulley and it’s only fractions of a mm away from bottoming out on the flat spot of the pulley. Once this occurs you can burn out the front alternator bearing very quickly due to the excessive heat.

Belt Mistakes Can be Costly

In this image we have a high quality Japanese made front bearing that was literally “burned out” due to frictional pulley heat. The bearing got so hot the front seal was destroyed and the grease was literally cooked out of the bearing. It then began to squeal & howl. If you look close you can see the heat damage emanating out from the shaft side of the bearing seal, and the gap in the seal where the grease was allowed to cook out of it. This was simply a case of attempting to drive too much horsepower with a single v-belt.

Pulley Ratio Considerations

Most performance marine alternators are specifically wound for low RPM performance. This means they can develop a tremendous amount of their rated output at a low engine RPM. At low RPM, for many marine diesels, this means a slower alternator fan speed. Low fan speeds with high output is were some of the most damaging heat can occur. Always pay attention to alternator temp at fast idle, if you plan to charge on-the-hook. If the alternator gets to hot reduce Belt Load Manager and / or add some forced air cooling to the alternator, via ducting and blowers.

Also, each alternator frame has a maximum design RPM. Some older marine engines, such as those by Volvo Penta, had massively large crank pulleys that can result in as much as a 5.5:1 pulley ratio. This can actually result in over-spinning certain alternator frames beyond their max design RPM limit. Before installing any performance marine alternator, on an engine with an overly large crank pulley, please check with the manufacturer of the alternator for the maximum safe RPM. You may find you need to up-size the diameter of the alternator pulley significantly.

Alternator Belt Shields & High Performance Alternators = Not a Good Match

I know we live in a world where lawyers are purportedly waiting around every corner to jump out and sue you into bankruptcy but, the Yanmar lawyers have taken this threat right over the top. The belt shields on newer Yanmars really do nothing but create problems dissipating heat from alternators. If you, as a boat owner, don’t know not to stick your hands into the belt of a running engine by now, perhaps you’ll want to consider a safer pastime. I hear Trivial Pursuit is pretty tame.

Balmar has lawyers too, and they advise drilling out the belt guard for better air flow. This can help but is really just a legal Band-Aid. Internal fan alternators draw cool air in from both the front and rear of the alternator and expel it out the center. Front fan alternators draw air in through the rear and expel it out the front. Belt guards like this do nothing but make it more difficult to have a cool running alternator.

In this image the alternator is sandwiched between a hot heat exchanger and the belt guard… It’s a darn good thing they installed an alternator temp sensor.

The choice to keep, drill or to remove your belt guard is 100% your decision. Please consider the safety risk carefully when or if you choose to remove it entirely.

Alternator Position – In or Out

Here’s an insider tip that can be considered when installing a high output alternator. Ask yourself these questions;

Where the manifold is in relation to the alternator?

Is it right behind it?

Do I have the room to tilt the alternator out a bit and get it away from the hot engine?

On many engines the alternator is designed to sit directly in front of a massive 180ºF to 210ºF heat source called a manifold. This particular engine room was not the best for photography but it illustrates an optional approach.

Here we are using the stock adjuster arm from Yanmar as well as the belt supplied with the serpentine pulley kit. Doing this places the alternator smack dab in front of the hot manifold making it tougher for the alternator to suck in the coolest air possible.

Stock Configuration

The choice was made to use a longer belt and adjuster arm, in this case the Balmar UAA or Universal Adjustment Arm. As can be seen the alternator is now out into cooler air and not stuck behind the hot manifold.

Optional Configuration

This owner really went to town and built his own adjuster arm to get the alternator out into cooler air. This is Balmar AT-200 with Alt-Mount Serpentine kit and the owner made his own adjuster arm to get the alternator out into cooler air.

Don’t be afraid to “roll your own“…

While cleaning the shop I found a template I had used for a custom large frame alternator installation. It was mocked up in cardboard, then 1/4″ plywood and then I made a drawing to give to our local machine shop. The drawings are nothing special. A custom adjuster arm, if necessary, is not very difficult. In 98% of the installations going to this level will not be necessary but it is just another option you have.

We have a few of these arms in-stock as it is less expensive, per piece, to do a run of ten of them than one. It is available at this link to the MHT web store: CMI Universal Alternator Adjuster Arm

Balmar has also made this easier, and less expensive than doing our CMI custom arm above, with the Balmar Universal Adjustment Arm also available in the MarineHowTo.com web store.

Alternator & Pulley Alignment

Perhaps the most critical step in an alternator installation is ensuring the crank pulley and alternator pulley alignment is good (water-pump too it they share a belt). In most cases, with a an upgraded alternator, they will often bolt right in and alignment will be pretty good but, it pays to check it, just to make sure.

We have two things we are looking at;

Angular Alignment Issues

Parallel Alignment Issues

Here’s an example of both an angular & parallel alignment issue:

TIP: If the alignment is so bad you can see it visually, it’s beyond bad!

Checking Alignment On-Board

When on-board, alignment can be checked pretty easily by using a straight-edge. By clamping a known true straight-edge across the front face of the crank pulley, and extending it to the alternator and water pump pulleys we can easily check both angualr and parallel alignment. Parallel alignment is usually the more common issue but, alternator brackets made by the engines marinizer, such as on a Westerbeke or Universal, can tend to create angular issues more often than a factory made alternator mount such as a Yanmar.

For this task I generally use some aluminum “L” stock or 1/2″ square tube stock tested on our cast iron planer table for flatness. Aluminum like this is available at just about any Home center. You’ll want the straight-edge to be able to extend to both the water pump and alternator pulleys. Once clamped to the crank pulley, you can simply measure the offset from the straight-edge to the very edge of the belt or to a pulley groove center. The measurement should match at both ends.

One measurement that is often confusing is when you have a crank pulley and alternator or water-pump pulley’s with varying face thicknesses. It does not need to be confusing. Once the straight edge is clamped to the crank pulley the measurement that’s important is from the straight edge to the belt edge or the center of the pulley V’s. If measuring to the center of a pulley V, on multi-rib pulleys, be sure to use the same v-groove at both ends. A divider can be used to compare end to end measurements by measuring one end then locking it and moving it to the other end. For these illustrations I have used a ruler and edge of belt measurements. Please do not use “to edge of belt” if the belt is not brand new.

This end is a prime example of why the pulley thickness is not taken into account. As can be seen the face thickness of the alternator pulley is less than the crank end. This is why the measurement that matters is from the edge of the straight edge to the edge of the belt or the center of a V in the pulley itself. In the event that the face of the crank pulley is thinner than the alternator pulley a piece of shim stock can be used at the crank end to space the straight edge out beyond the alternator pulley.

For angular alignment the straight edge should be the same distance from the straight edge at both side of the pulley. In the photo above we can see the gap between the pulley and straight edge is perfectly parallel and angular alignment is also not an issue here.

The image below represents a case where the crank pulley’s face is much thicker than the alternator pulley’s face. A measurement was made at the crank end first, from the straight edge to the pulleys second groove and then repeated at the alternator pulley end and the two offsets were compared. The distance was essentially 23.15mm at both ends or darn near perfect alignment..

“What about laser alignment tools?”

We own a couple of these laser tools and all I will say is save your money, unless space is really, really tight.  The tricks you’ve just seen remove the need for these expensive tools and the laser alignment tools do no better of a job. A $3.00 piece of aluminum stock and a ruler or your navigation dividers from your chart table are a lot less than the cost of a Gates Drive-Align Laser or similar.

Shimming & Spacers for Alignment

Occasionally you can run into a situation where the aftermarket alternator is off by a bit. For Yanmar fit alternators the most common need for alignment is to shim forward. This is good because with a dual-foot alternator, if you needed to move aft, you’re either moving the alternator mount or machining off some of the foot.

In this image two washers have been used behind the Yanmar fit alternators front foot to get the correct pulley alignment. The washer closest to the alternator foot was sanded on a piece of glass, using wet sand paper, until the correct thickness was attained. This can take a while but the right thickness washer was just not readily available. If you know the thickness you need a machine shop can also make you any spacer you need. Any washers used for shimming should ideally be the same ID as the alternator pivot bolts OD. In other-words if you have a 3/8″ OD pivot bolt use a 3/8″ ID washer and if you have a 10mm pivot bolt use a 10mm metric washer.

Yanmar 3.15″ Dual Foot – Shim Forward

Dual Foot / Saddle Mount Alternators Can be Quite Flexible

In this image we have a Westerbeke engine that used a teeny-tiny 1″ foot Mitsubishi alternator that really conformed to no “small-frame” standards other than its own. Westerbeke offers a bracket to convert to a Balmar or other 1″ or 2″ foot Delco/Motorola/Bosch frame type alternator but the pricing for this bracket is literally insane.

When a 1″ or 2″ foot alternator can’t work the 3.15″ Yanmar style dual-foot alternators can often be used in place of a 1″ or 2″ foot mount as seen below. This image shows a Balmar 6-Series dual-foot alternator mounted to the factory Westerbeke engine mount (red part). Alignment has been set and  mocked up using shims and washers. Once the shim & spacer dimensions are known you can then hit a machine shop and have them make you the correct spacers in a one-piece design. In this case the multiple pieces behind the red engine mount and in front of the alternators rear foot, would be combined into one nicely machined spacer. You can always leave it as pictured too. I just prefer less shim-parts as opposed to more.  I have noted what I refer to as the drift bushing in the rear foot more on this soon.

Here’s an example of what it looks like to have the spacer and shim pieces machined to minimize excess part count..

Dual-Foot Alternator Rear Foot Bushing

The Yanmar style 3.15″ dual-foot alternators (also called “saddle mount” or “Hitachi mount”)  as well as the 4″  dual-foot J180 large frame alternators both use what I refer to as a rear foot “drift bushing“. It is really just a split bushing that is machine pressed into the rear foot but other than “drift bushing” it really has no identifiable name. It does however deserves some brief discussion.

This bushings sole purpose is to compress the front foot of the alternator between the pivot bolts head and the alternator mount. It also serves to “support” the aft end of the alternator. Under no circumstances should the drift bushing ever be removed and the two feet of the alternator “clamped” by the pivot bolt..

This owner of a brand new alternator did not know what this bushing was for, so he removed it.. Oh jeez…….

This is a saddle mount / dual foot drift bushing:

This image illustrates where the clamping pressure is applied with a “dual-foot” alternator. Only the front foot is under clamping force pressure. The rear foot is merely providing support. You can see pretty easily with this Yanmar alternator bracket why removing the drift bushing can result in breaking of the alternators mounting feet.

When installing a dual-foot alternator following the guidance below will result in a worry free installation:

Alternator Pivot-Bolts

An alternators pivot bolt would appear a rather mundane item to discuss but, using the wrong bolt can get quite expensive. In the image below the engine blocks aluminum alternator mount has been  damaged by the use of the wrong size pivot-bolt. Using the wrong size bolt, one that is undersized, can allow the alternator to twist, under belt-load and can potentially cause damage.

If you let the above continue and ignore checking your belt tension and alternator when you check the oil. This damage destroyed the entire front timing gear cover of the engine.

Alternators are also susceptible to pivot bolt damage:

Adjuster Arm Issues & Solutions

Issue #1

An alternator adjuster arm is normally just a piece of plate steel that connects to the engine on one end and the alternator on the other end. Its sole purpose is to keep tension on the alternator belt. The steel arm is normally slotted, as can be seen below, and the bolt clamps the alternators adjustment ear to the adjusting arm. One problem with this is that the alternator ear is soft aluminum and the aluminum gets pretty hot. Through repeated expansion & contraction cycles, and on high vibration diesels, the bolt can often become loose as happened in the left side image below. In this case the bolt actually fell out completely.

Issue #2

The second issue I see, with fairly high regularity in regards to adjustment arms, is a relatively thin washer trying to apply pressure to the slotted arm. Due to the slot there’s limited surface area to actually grab onto. What often winds up happening is the washer begins to “dish” or “cup”.  Once it does this the original torque/tension is lost and the alternator ear looses its grip on the arm can slip and allow the belt to become loose. The grip on the adjusting arm below was lost when this washer “dished” under load.

Solution’s for Issues #1 & #2

In order to alleviate the issues associated with the images above I recommend using a bolt that will extend all the way through the alternator adjustment ear far enough to accept a washer, lock washer and a nut. A Nyloc or other locking nut is an added benefit here as nylon has a much higher melting point than your alternator should ever see. On top of the longer bolt the use of *an extra thick washer, such as the CMI Grip-It Washer will eliminate washer dishing & arm slippage.

*The Balmar AT-165 uses an extra thick washer on both sides because the adjuster ear has a vertical slot in it. For threaded ears an extra thick washer on the adjusting arm side is all that is usually necessary.

Setting Belt Tension

Just like belt alignment, belt tension is critical for optimal alternator performance. Too much tension is not going to necessarily be better than too having little tension. Both extremes are bad. Guessing at belt tension, using the Binford Mark I Thumb Press Tool,  unless your really experienced with this, is not likely to result in a good outcome. New belts also need to be “run in” and then re-adjusted. In other words don’t just install a new belt adjust it and walk away. You’ll want to run the belt under load for a period of time then make a second adjustment.

The first step in setting belt tension is to identify the longest pulley span as show below.

Once you’ve identified the longest belt span you can click on over to the Gates web site and used their V-Belt Tension Calculator. Simply input the type of belt you have, the belt width and whether the belt is new or used and it will give you a belt tension number to start from.

Now that you know what belt tension you need, use of the Gates KRIKIT tools can be used to measure the actual belt tension. A pencil styl tool can also be used but they are more difficult. The Gates KRIKIT tools are inexpensive and pretty easy to use.

Just place the tool in the middle of the longest span, align it in parallel with the belt and press until you hear/feel it “CLICK”. Now carefully remove the tool and read where the plastic arm is flush with the aluminum gauge. There are two Gates KRIKIT tools one goes to 160 pounds and the other to 320 pounds. The most useful for our applications is the KRIKIT II PN 91132 (bottom tool in image below).

Balmar Serpentine Belt Tension:

For Balmar AltMount J10 belts, these are adjusted similarly, by deflection, but not to the same spec as a v-belt. With a 10-groove J-section belt, the correct tension is 1/32” of deflection, for each inch of belt span between pulleys. Deflection pressure is 25 pounds applied in the middle of the longest span. A “pencil type” deflection tester, such as the Gates 7401-0076 is used to test for the 25 points of deflection.

Setting Belt Tension:

For placing tension on the belt I am pretty old school. I still use, nearly 90% of the time, a pry-bar with some heavy duty heat shrink over it. It works really well and the heat shrink prevents scratches on engines and alternators. You just need to find a good point to land it on the engine and alternator.

At the shop here, we also own a product called a Supco Belt Jack. This one, shown on top in the photo below, is the shops fourth and last one. I find this tool entirely under-designed and woefully inadequate. Hopefully this can save you some headache and money. This one is brand new because the last three broke where the pulley pad meets the jack. The welds seem to fail no matter how careful you try to be with it. Even when they do work, and it will for a short period of time, I still prefer the old school pry-bar method. If you feel you want a belt-jack, to adjust your belt, one can easily be made from an old turnbuckle for a lot less money. Done correctly it will likely also be considerably more robust than the Supco Belt Jack.

The best & easiest way we’ve found to adjust alternator belt tension is with the Balmar UBB – Universal Adjuster Arm With Belt Buddy. This is an excellent addition to any alternator upgrade you’re considering tackling.

Good luck with your project and happy boating!!

A 30A Galvanic Isolator

WARNING: The galvanic isolator used in this article does not meet the current safety standards. To meet the current safety standards you would need a “Fail Safe” unit that has been tested to the ABYC Fail Safe standards.

The ProMariner ProSafe FS30 & ProMariner ProSafe FS60 both meet the current Fail Safe standards.

Why you’d need a Galvanic Isolator?

What exactly is a Galvanic Isolator (GI), why do you need one & why on Earth would you need to test one? These and other questions will all be answered in this article.

A galvanic isolator is a device that is inserted, in series, into the AC green grounding wire (safety ground) of your shore power feed to help minimize or reduce the effects of galvanic current from flowing into your vessel. While the purpose of the GI is blocking galvanic level current, it also has to allow for the passage of AC fault current. GI’s are a very simple hook up and installation, even for the average DIY, but ensuring you never lose your AC safety grounding conductor is of critical importance.

If plugging in at a marina a GI is a bare minimum level of protection a boat owner should have. Here at Compass Marine Inc. we absolutely prefer an isolation transformer (IT) over a GI but the conversation of a galvanic isolator vs. isolation transformer is a whole other discussion & topic. If you plan to plug into shore power, you’ll need a galvanic isolator at a bare minimum.

To install a GI all one needs to do is to break the green wire, after the shore power inlet, but before the AC panel.  Simply cut the AC green wire in two, crimp on two terminals and connect them to each stud. Not many electrical jobs on boats are this simple. As mentioned above the purpose of a GI is to block low voltage galvanic level DC current while still allowing any AC fault current to pass through the green wire to ground and allow it to activate fault protection devices.

This blockage of low voltage DC galvanic level current is achieved by using two diodes in each direction. Each diode drops approximately 0.6V or put another way requires more than 0.6V to open and allow for current to pass. Two diodes in series results in approximately a 1.0V – 1.2V threshold for blocking galvanic level current. The reason for having two diodes, in each direction, is so the green wire is not simply check valved or blocked and acts just like a wire would. In other words it allows fault current to flow through the wire for human safety. The critical difference between a bare green grounding wire is a GI, is the GI won’t allow the passage voltages/current below 1.2V. Simple, and is effective at blocking galvanic level current.

What is Galvanic Current?

The creation of a galvanic current occurs when dissimilar metals, with differing galvanic voltages, are immersed in an electrolyte (water). The more noble metal survives while the less noble metal (anodic) becomes the anode and is eaten away from the galvanic that’s current created by the differences in voltage potential of the different metals. This is why we use what are called anodes to protect our expensive under water metals. Anode materials include Mil-Spec aluminum, zinc or magnesium. These metals serve as the least noble metal in order to sacrifice themselves and protect/save your brass, bronze or other underwater metals from galvanic corrosion.

Metals have voltages?

Yes, each metal has a voltage potential. Data for this can come from any number of Galvanic Series or Galvanic Scale charts. For example a zinc anode can range from -1.00V to -1.07V and graphite, think graphite impregnated packing material or PSS shaft Seals, is upwards of +.2V. It is the difference in electrical potential, when immersed in an electrolyte, that creates the galvanic current that eats away the anodic or least noble metal.

The galvanic series/scale of metals represents a difference in voltage potential, between the most noble of metals (approx +0.2V) and the the most anodic metal (approx -1.4V) of about 1.2V. If you just realized that a GI blocks voltages below 1.2V pat yourself on the back as you now understand what a galvanic isolator is doing.

What is a diode?

Think of a diode as an electrical check valve. A diode allows current to flow in only one direction but not in the other direction. One of the inherent traits of diodes is the voltage drop associated with them, which is usually around 0.6V. In a galvanic isolator application however, they have used this often assumed less desirable trait of a diode to an advantage. By wiring two diodes in series you now have a device that can block any galvanic created current at voltages below 1.2V from flowing into or out of your vessel. The GI blocks galvanic currents from flowing between dissimilar metals and protects you from galvanic level currents in the marina when you plug-in.

Simple Devices

As mentioned above these are simple devices. When opened up you can see just how simple. It is important to note that this particular model no longer meets the current ABYC safety standards. I will get why in a moment. On the back wall we can see the two wires going to the gold plated studs. This is where your green grounding wire would be cut and connected to. Inside we can see the two diodes which allow current to flow in both directions but at the same time blocking voltages below 1.0 – 1.2V.

So why do I need to test my GI?

Remember in the last paragraph when I mentioned this particular GI no longer meets the current ABYC safety standards? Well,there is a very good reason for that.

Think back to when I described where a GI gets installed? It is inserted in the GREEN SAFETY GROUND WIRE. What happens if one or both of those diodes gets blown? You guessed it, you now have no NO SAFETY GROUND. Over the years there were far to many incidences of boats, with GI’s, that completely lost their safety ground connection to shore due to failed diodes.

A single lightning strike on a boat a few docks away could take out half the GI’s in the whole marina and folks rarely even noticed. Honestly ask yourself when you ever heard of someone testing a GI? Right, you’ve most likely not. Couple this with the fact that many more boats are not wired, on-board, to current safety standards where the AC green/grounding wire is bonded to the ships DC grounding bus and this means metallic parts of AC devices could become “hot” in the event of a fault. Hot cases and metallic parts of your boat spell the potential for electrocution or death to occupants or to swimmers by electric shock drowning. Without the safety ground connection to shore the fault protection devices will not trip as they should. This = BAD/DANGEROUS

Below is a direct quote from Captain David Rifkin. David is perhaps the leading expert in marine electrical shock drowning deaths, bonding and corrosion.

“In the many boats I have tested with galvanic isolators, approximately 5% tested open circuited (meaning the boat did not have a connection to the marina grounding system) and the operators were completely unaware.”

I know 5% of the boats with GI’s, and an open circuited ground, does not sound like much, but consider that with the millions of boats in the water there are potentially hundreds of thousands of GI’s installed on boats. How many boats in your marina? 100? So if 5 of those boats are completely lacking a green safety ground wire, do you want to go swimming in your marina? Course we all know we should never swim in a marina, but it happens.

What does meet the current safety standards for GI’s?

The ABYC standards for galvanic isolators have changed a few times over the years. The first iteration required “active monitoring“. This was in the form of a  remote lighted panel so an owner could glance over and know they had a safe and operational GI with the safety ground intact. This “active monitoring” added significantly to the cost of GI’s and was a total PITA in terms of parasitic loads because it had to be “wired in” to more than just the green wire. It also created an issue with ELCI’s and GFCI’s as it “pulsed” the safety ground which could cause nuisance tripping.

A number of years ago a company called Dairyland Electrical Industries, or DEI for short, invented/brought the “fail safe” galvanic isolator to the marine market. This advancement brought simplicity, and no monitoring, back to the GI  and did away with the idiot lights and related circuitry. Unlike traditional diodes that tend to fail open the fail safely diodes fail closed and all you lose is galvanic protection. Today the ABYC standards require the use of Fail Safe galvanic isolators such as the ProMariner ProSafe FS30 or the ProMariner ProSafe FS60.

The designation FS or fail safe means that these devices fail closed instead of open as a normal diode would. By failing closed you only lose galvanic protection but not your SAFETY GROUND to shore. According to Henry T., one of the owners of DEI, they have not had a single failure of a DEI Fail Safe galvanic isolator where it failed “open”, even to lightning strikes. A pretty impressive feat considering the number of failures that occurred with the older technology, like the one you see here. The results for the ProMariner’s mentioned above are the same, no known unsafe failures.

Today companies such as ProMariner & DEI both make ABYC compliant galvanic isolators with the fail safe technology. Yandina & Sterling Power also make GI’s (we are a Sterling Power Dealer) but they do not meet the current ABYC safety standards so we do not sell nor do we install them. I do mention both of these products though because both companies are at least 100% honest that the product does not meet the current US safety standards. Kudos to Yandina & Sterling Power for being honest in a world of BS marketing hype.

If you’re a mooring sailor who rarely stays at a dock the Yandina GI or Sterling Power GI can represent a value purchase but they must be routinely tested. If adding a GI, for regular dock side use, we strongly advise installing a fail safe product.

How To Test

Switching To Diode Test

With this meter pressing the yellow button moves it from the Ω test to the diode test feature. The diode symbol can be seen on the left hand side of the meters screen.

*Connect Your Test Leads

*UNPLUG YOUR VESSEL FROM AC POWER BEFORE TESTING

With the AC power to the vessel OFF/Physically Unplugged, check your inverter too, disconnect both green wires from the GI and connect your DVM leads to the studs.

If the diodes are working you should see a reading of .8 to 1.0. here the reading is .973. If the diodes are bad you will not get a reading or will get the OL message (open leads) if using a Fluke. Older style galvanic isolators like this fail open.

Now Reverse The Leads

Remember, the current needs to be able to flow in both directions, just like a piece of wire, and it is possible for one side to be blown and the other side still be fine.

Here the reading is .968 and well within range. You are allowed roughly a 10% variance from one side to the other so .968 and .973 are well within that spec at a 0.5% variance. Despite being a relic from days past, this isolator is still operable.

If however you have an old isolator like this, and you keep your boat at a marina, I would strongly advise upgrading it to newer ABYC compliant fail-safe unit. The only other alternative is to regularly test your GI to ensure it is operational.

Our preference for GI’s are the DEI or ProMariner Fail-Safe galvanic isolators. We offer the ProMariner Fail Safe’s, to our readers, in the MarineHowTo.com Web Store.

You Don’t Need A Fancy or $$$ Meter

I certainly love our Fluke test equipment, we abuse the living snot out of it, and it survives. However, for a DIY, especially one on a budget, even an inexpensive meter will do. You just need to ensure it has a diode test function. Many “el-cheapo’s” do. Heck, the one in the middle is from Wal*Mart and costs less than a 12 pack of Bud Light.

In this photo each meter has been set to the diode test function.

The Diode Symbol

Set To Diode Test

On this meter the diode test function shares a dial position with the audible tone continuity test. This meter was about $14.00 at Wal*Mart.

Diode Test

On the Fluke 179 you simply toggle between the diode test and Ω with the yellow button. When in doubt pull out the manual for your meter.

Alternative Test

While you’d be best to use the diode test functionality of a DVM, you can do a quick and dirty test with a 9V battery and a 12V light bulb. I don’t recommend using an LED bulb for this test. I grabbed an LED bulb only because it showed up better in pictures. You will get a dimly lit 12V bulb with a 9V battery but the test works.

If you first connect your bulb direct to the 9V battery then test it through the isolator you will notice a change in brightness. This is caused by the voltage drop across the diodes and is 100% normal and should be expected.

Wire the 9V battery and incandescent light bulb as shown (not an LED) and the bulb should light if the diodes are good.

Reverse The Leads

Again, just like with the diode test function on the DVM, you’ll need to reverse the leads to check the flow in the opposite direction. The bulb should light.

Newer GI’s have a remote panel display, that tell you it is on & working, or they are fail-safe so there is much less need to worry about losing the safety ground and really no real need to test them.

This test procedure is for older style GI’s similar to the one pictured. There are still perhaps hundreds of thousands of boats with this style GI installed on-board.

Blocking Current @ 1.1V

This is a test most owners won’t be able to conduct, unless you have an adjustable bench top DC power supply or a 1.5V battery and some diodes to drop the current below 1.1V.

In this photo I’ve set the power supply to 1.1V DC and am measuring the current with the Fluke meter. As we can see, based on the Fluke meter, the diodes in the Galvanic Isolator are doing what they are intended to do, block DC current to 1.1V.. The Fluke reads 0.00A DC and this is how it should perform.

Current Flowing @ 1.3V