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.

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!!

Preface

This article contains three separate videos that show how to physically program Balmar regulators. The videos are meant to be watched in conjunction with reading this article so the misconceptions and misunderstandings I have identified over the years, regarding these regulators, can be explained with a bit more depth.

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UPDATE: Since this article was written Balmar’s new MC-618 regulator has been launched. The new MC-618 allows programming via the screen on the Balmar SG-200 battery monitor or via the SG-200’s Bluetooth App. It can also be programmed the same way as this article describes.

The Magnetic Reed Switch

For years I’ve listened to customers express concerns about “how difficult it is to program the Balmar regulator“, and I don’t necessarily disagree with this, especially if you’re a DIY or one who does not do this on a regular basis. Even for myself I can find programming a customers, already installed, Balmar regulator a bit tedious.

This article will help:

• Give you higher a comfort level in programming these regulators
• Clear up some of the confusing language in the owners manual
• Provide you with a “Regulator Programming Cheat Sheet“
• Discuss best practices for programming & installing these regulators
• Provide tech tips that will make the process easier.

This article features the Balmar MC-614H but programming & features are similar for the Balmar ARS-5H.

IMAGE: Pictured here is the Balmar MC-614’s magnetic reed switch location, as identified by the red dot.

Definitions: The Balmar owners manuals covers what the LED screen codes mean such as A1C, FFL, AGL etc. etc.. There is no need for us to repeat what is already in the manual in terms of what the numbers/letters are telling you, unless we believe them to be confusing. We have addressed the most commonly confusing parts of the manual, based on years of supporting these regulators, in the article. Please familiarize yourself with the owners manual before reading this article. With the manual and this article it will make more sense.

MC-614 Owners Manual .pdf Download

Why Choose a Balmar Regulator?

Why do I prefer to use the Balmar regulators vs. the other external regulators that are out there? FEATURES! There is no other external voltage regulator, other than DIYing your own, that compares feature for feature with the Balmar regulator. Balmar also delivers excellent customer service and tech-support where humans, that actually know something, answer the phones.

Reliability:

Despite what you you may read on the internet, even by me, because I had an early failure of an ARS-4 & experienced a few others too, these regulators today are very reliable. Over the last 11+ years and many hundreds of regulators I’ve had one regulator with a bad reed-switch (replaced immediately) and one the customer claimed was faulty, but when sent back, was in perfect operational order. Due to changes made over the years to improve reliability, this regulator underwent a full suite of testing, and I got a report from CDI/Balmar. This level of testing was done because these failures are now so rare.

Early on there were some failures of ARS-4’s and some MC-612’s but changes were made to make them more reliable in the move to the current generation. Since CDI Electronics purchased Balmar they have been even further refined for the ultimate in reliability.  I’ve not experienced a single regulator failure under the new CDI/Balmar ownership.

Programming & Control:

In today’s day and age there is simply no excuse for any DC charging product that uses “dip-switch” type programming. By dip-switch I mean programming that utilizes a typical three setting;  AGM, FLOODED or GEL setting. DC charging products like this, in today’s day and age, are simply antiquated tube TV era products. They really have no place being sold in this century other than to pick your pocket. Please do your best to avoid “dip-switch” set battery chargers, solar charge controllers and external voltage regulators that do not allow you to have full-control over your charge settings.

There are no commercially available external regulators, at this price point, that allow you the same level of programming & control that a Balmar does.

• Base Battery Type
• Belt Load Manager (can also be used for current limiting an alternator)
• Display Mode
• Alternator Failure Advisory
• Regulator Field Start Delay
• High Voltage Limit
• Compensation Limit
• Bulk Voltage Limit
• Bulk Time/Duration
• Absorption Voltage Limit
• Absorption Time/Duration
• Float Voltage Limit
• Float Time/Duration
• Low Voltage Limit
• Field Threshold % Bulk to Absorption
• Field Threshold % Float to Re-Absorption
• Alternator Temperature Threshold Limit
• Battery Temperature Threshold Limit
• Battery Compensation Slope Voltage Correction

The majority of the programming features above are non-existent on other external regulators.

Regulator Installation Best Practices

Balmar regulators use an epoxy potting to keep the regulators printed-circuit-board clean, dry & free from corrosion. Placing it in high-heat areas can increase the risk of the epoxy potting to crack, as shown. I prefer to see a maximum working temp of below 140F, but Balmar claims the regulator can now handle 194F with the newest potting epoxy revision.

The regulator in the image above was installed by a boat yard, yet it was installed in the engine bay and only inches from the exhaust riser & manifold. The high heat and rapid temp changes caused the epoxy potting, which makes the regulator highly water resistant, to crack. The cracks in the epoxy likely causing one of the traces or components on the PC board to fail.

This regulator was also located near the engines siphon-break and had some corrosion starting on the terminals. This regulator was replaced and relocated outside the engine bay. After replacing it we ran the boat for other purposes and I noted a surface temp where the regulator used be of 208F. This failure is not a result of the regulator but rather a very poorly chosen installation location.

Regulator Installation Worst Practices:

• Avoid installing the regulator in the engine bay unless yours runs pretty cool
• Do not install the regulator in a hot compartment or against the inside of a dark colored hull
• *Do not wire regulator negative to the back of the alternator
• *Do not wire voltage sense to the back of the alternator
• Do not just set a battery type and walk away
• Do not forget proper over-current protection / fusing
• Do not clean the epoxy potting with any solvents
• Do not use Velcro to affix your regulator to the vessel, there are four screw holes for a reason

Regulator Installation Best Practices

• Install the regulator in a cool & dry location, quite often this will be outside the engine bay
• *Wire positive & negative voltage sensing directly to the battery being charged or as close as possible
• Always use the advanced programming menu to get an optimal set up
• Always program the alternator specifically for your batteries
• Program the regulator at home rather than once installed, it give you much better control
• Always use the optional battery temp and alternator temp sensors (MC-614H offers two battery temp sensors!)
• If you need to extend the wiring harness make one yourself rather than adding onto the factory harness with hidden splices
• Always program your regulator to avoid dropping to float too early. I call this “premature floatulation“
• Always use proper crimp tools & terminals
• Always use over-current protection on any positive feed to the regulator Reg B+/red, #9 / v-sense and Brown / ignition
• Try to mount the regulator in a vertical orientation
• Maintain a decent distance from RF noise emitters such as the alternator itself, inverters, chargers etc.
• Allow for adequate air flow around the regulator
• Use the Balmar supplied magnetic screwdriver, it has the correct magnet strength for the reed switch.

*Please read this sister article on proper voltage sensing for the best charging performance.

Alternators & Voltage Sensing – Why It Matters

Installation Location

Over the years Balmar has had some varying advice on where to best install the regulator. This particular manual for an MC-614 (see image) says to avoid engine bays due to high heat. I tend to agree with this particular manual, unless your engine bay runs cool and is well ventilated.

The MarineHowTo.com Regulator Programming Cheat Sheet

*Click on image to enlarge

In order to help make the job of programming a Balmar regulator easier, MHT created a programming cheat sheet just for this purpose. This .pdf file allows you to print it, then go through each setting before hand. You simply choose what you want to change/set and enter it into the cheat sheet before you start programming. The cheat sheet follows the MC-614’s scrolling menu.

TIP: When you’re all done programming the regulator, please save your programmed settings by inserting the “programming cheat sheet” into your on-board owners manual. Now any service tech that gets on board will know exactly how your regulator is programmed. They will really appreciate this information and it may just save you a lot of time and money.

IMPORTANT: Please purchase batteries from manufacturers who can provide you with all the parameters necessary for proper programming.

This is a free printable .pdf download:

Regulator Programming Cheat Sheet Download – Click Here

Custom Cheat Sheets:

If you would like us to create a custom cheat-sheet for you, the flat fee is $65.00. Before you contact us please read the following;

1- We only do custom cheat sheets for genuine branded batteries such as Lifeline, Trojan, US Battery, Northstar, Odyssey, Crown, Deka/East Penn, Rolls, Fullriver etc.. We do not make cheat sheets for batteries sold by “sticker application companies” such as auto-parts stores, West Marine, Costco, or cheaply made off-shore batteries such as Renogy or most any non USA made battery sold on Amazon. If the sticker on your battery is not an actual physical battery manufacturer, please do not contact us for a cheat sheet.

2- We DO NOT make custom cheat sheets for LiFePO4.

3- You must provide us with a complete description of how you use the boat, daily Ah consumption, all charging equipment including brand, make, model and amperage. Also, if you have an externally regulated alternator we will need to know what belt you are driving the alternator with and the amperage of the alternator.

Regulator Cheat Sheet Example

*Click on image to enlarge

In this image, and downloadable .pdf, we have an example of a regulator cheat sheet all filled out and ready to program the alternator for a GEL battery. This is simply an illustrative example of what a filled out programming cheat sheet might look like.

Regulator Programming Cheat Sheet Example Download

Why is Belt Load Manager a Tremendous Feature?

Belt Load Manager, formerly known as Amp Manager, is a feature unique to the Balmar family of regulators and is built into both the MC-614 and ARS-5. It is programmed using bEL in the regulator programming menu. I know of no other external regulator, other than Wakespeed, that offers any way to limit the alternators current output to accommodate a belt limit situation or to reduce the chances of the alternator from over-heating.

Lets use this alternator as an example:

This owner replaced his 80A factory alternator with a 110A Balmar, only his existing regulator was not a Balmar, but rather a an older Xantrex/Heart Interface. This was a very bad idea. The old Xantrex regulator, like most others out there, had no way to limit the alternators amperage output to better match the v-belts capabilities. The belt on this engine was a 1/2″ or 13MM single v-belt, the standard belt for this engine. Using the factory 80A alternator belt dust was tolerable but two factory alternators burned up trying to feed the massive bank of AGM batteries so the owner sought higher performance.

Once the owner switched to the 110A Balmar alternator he began chewing up alternator belts at a rate of one belt for every 16-22 hours of engine run time. Wow!!!! The belt dust was literally choking everything including the alternator. Alignment was spot on, pulleys were clean and rust/corrosion free and the belt wrap on the alternator pulley was actually quite decent too. The problem was simple, he was just overloading the belt and had no way to limit this issue other than dual v-belts $$$$, a serpentine pulley kit $$$$, or a better designed regulator $$. The owner chose a Balmar regulator and belt manager was set to level 5. Belt dust was nearly eliminated and he went three years on the next belt. Ideally this situation required dual v-pulleys, or a multi-rib / serpentine kit, but with the Balmar regulator and Belt Load Manager, he was able to make it work and at a much lower cost than a pulley conversion.

IMPORTANT: Just because you purchase a 100A alternator don’t be fooled into thinking this is its maximum output. When cold a typical performance based small case alt can pump out 5%-15% more than its face value cold rating or 105A to 115A +, for short duration’s, even with a 100A rated alternator. Some brands will deliver more than 20% over the rating when cold. This overage, even for short duration’s, wreaks havoc on belts. Only Balmar regulators offer the Belt Load Manager feature.

Belt Load Manager can be used to solve two important issues:

#1 Limit an alternators output to better match the v-belts HP drive capabilities.

#2 Limit an alternators output in high demand/long bulk situations to allow longer alternator life by running it at less than “full bore/full output”. Contrary to popular misconception I know of not a single small case alternator that can be run at full output for hours on end, unless;

1. The rectifier has been removed and the unit is rectified remotely
2. It uses liquid cooling
3. You are directly force feeding it ice cold air while also exhausting the hot air

For example, if your desire a hot alternator output of 85A – 100A then you would ideally want to purchase a 120A or larger small case alternator and use Belt Load Manager in order to limit the alternator output to your target amperage. Sizing this way keeps your alt running cooler and keeps it within its safe operating envelope, in regards to a safe working temperature.  Again, only Balmar regulators have the capability to limit the alternators field potential.

IMPORTANT: Small frame / small case alternators, even those sold as high performance, are NOT CONSTANT-DUTY RATED.

Don’t be fooled by less expensive regulators which lack features and lack the programming the Balmar regulators have.

Belt Load Manager Misunderstandings?

Below is a direct quote from the Balmar manual:

“The MC-614 provides the ability to manage regulator field potential, making it possible to govern the horsepower loads placed on the drive belt(s) by the alternator. The Belt Load Manager can also be used to protect the alternator from extraordinary load created by a battery load that’s too large for the alternator’s capacity.”

I have highlighted the words “field potential” for a reason and that reason is because Belt Load Manager (BLM), and how it actually works, is very often misunderstood.

Each step in BLM results in a 5% reduction off the maximum available field potential (click the image to enlarge it). It’s important to understand that BLM is not a 5% reduction in amperage output on a 100A alternator, or a 20% reduction in output for a 150A alternator making the 100A a 95A alternator and the 150A alternator a 120A alternator. This is not how it works, but it’s how many folks assume it works.

What is Often Assumed or Misunderstood

*100A Rated Alternator

BLM #1 = 95A Alternator

BLM #2 = 90A Alternator

BLM #3 = 85A Alternator

BLM #4 = 80A Alternator

BLM #5 = 75A Alternator

*100A alternator used as example only

The reality is this is not how BLM works. We have RPM, rotor core resistance, battery voltage, cold alternator windings and hot alternator windings etc. all playing a role in its overall output and field demand.

As an overly simplified example, consider BLM this way;

If your alternators field could pull max of 6A, at a given RPM, field voltage & stator/rotor temp, and you then set the regulator to BLM #1, the field potential (field voltage), the alternator could see, based on all the previous criteria, is reduced by 5%.  This 5% reduction, in avaible field voltage, would result in less than 6A driving the rotor.

What is “Field Potential”?

Field potential, for a Balmar regulator, is battery voltage (sensed voltage) minus about a 0.4V to 0.5V drop across the regulator FET’s. So a battery voltage of 13.5V, during bulk charging as voltage is climbing, results in a field potential of about 13.0V to 13.1V. If we follow Ohm’s law, voltage is what drives our current, and the same is true into a alternators rotor. BLM reduces the available field voltage, measured after the FET’s, by 5% for each step. If we reduce field voltage (field potential) we also reduce field current and alternator output *generally goes down.

*Generally - Occasionally a single BLM step will not reduce output because the regulator is slightly over-driving the rotor to begin with.

Keep in mind that if you set up belt manager, into a hot alternator,  it will still produce more current when it is cold. If you set it up at a low RPM it will be different than at a high RPM.

Bottom line is that BLM is a reduction in the avaible field potential (field voltage) not a reduction in alternator output based on it’s “rated output”.

There are a few ways you can program this:

•      Reduce BLM in steps, over a few week period, with good solid runs in-between that would be sufficient to generate belt dust. Reduce BLM until you no longer have belt dust or you are no longer bouncing in and out of alternator temp limiting.

•     Beg borrow or steal an inverter that can load your alternator to its maximum output and set your engine at cruise RPM. Now use a DC clamp meter or other ammeter to measure alternator output amperage. While the engine is running reduce BLM until you are at your desired maximum output at cruise RPM. It will still be higher when the alt is cold but not for very long. If concerned about cold start load, reduce BLM by one more step.

Belt Load Manager is just PWMing (pulse width modulating) the field output during periods that would otherwise result in 100% regulator field output.

Program The Regulator Off the Boat

One of the easiest ways to program a Balmar regulator is at home, with a 12V source. It is simple, and requires only 4 wires for the MC-614, or 3 wires for the ARS-5. You’ll also want a fuse or fuses to do so this safely. In this image I’m using a small 12V GEL battery. I use this battery for testing mast wiring during spring commissioning. I have added a fuse block and three fuses; Ignition, Regulator B+ and regulator Volt-Sense plus the yellow regulator B-/Negative lead.

Programming the regulator, in comfort, is much easier, less stressful and you can easily double or triple check your work all while not having a hose-clamp tail piercing your backside. I pre-program every single Balmar regulator I install, here in the shop, before I even get to the boat.

Required Connections for Bench Top Programming:

Regulator B-/Negative – Yellow or Black Wire Terminal #1

Regulator B+/Power – Red Wire Terminal #2

Ignition / Brown Wire Terminal #3

*Voltage Sensing – Terminal #9 (*MC-614 only ARS-5 does not have a terminal #9)

IMPORTANT: Battery or source voltage must be at a minimum of 12.5V in order to program the regulator & have the changes save.

TECH TIP: Please fuse all positive wires (+ volt-sense, B+ & Ignition). Hooking the regulator up backwards, without fuses, can destroy it.

Programming The Base Battery Type

It is best to tackle the programming in three distinct steps with battery type being first:

1- Program the base battery type; bA

2- Program the next three settings of the hierarchical menu; bEL, dSP & bDL

3- Program the Advanced Settings

In the first video the MC-614 is programmed for the base battery type or bA:

The reason for programming the base battery type first is to prevent confusion down the road.  Let’s assume you left the regulator programmed to UFP or “Universal Factory Program” but then went in and created a full custom charge profile, in the Advanced Settings menu for your GEL batteries. The first thing a tech will do, when there is an issue, is to look at the UFP setting, then look at your GEL bank, and change the battery type to GEL. They may do this despite the fact that you have proactively changed the GEL or AGM or FDC settings in Advanced Programming, to exactly match your brand & type of battery. Correctly setting the battery type just prevents confusion.

The Programming Hierarchical Menu

The menu you see in this image represents the top line menu items that you’ll scroll through to program the regulator. Each hierarchical menu item is a gateway to change what that top-line menu represents.

TECH TIP: You do not need to go through each step each time. For example, if you made a mistake setting Belt Load Manager or bEL, but everything else is correct, release the magnet after “PRO” appears, then re-touch at bEL to set or change Belt Load Manager. Once you’ve fixed bEL just let the display scroll three times until you see SAU, which means SAV or SAVE, you’re now all set.

Hierarchical Menu In Scroll Order

bA = Set Battery Type –  The gateway to set battery type eg; AGM, GEL, FLOODED etc.

bEL = Set Belt Load Manger Percentage – The gateway to set BLM eg: level 4 is a 20% reduction in field potential

dSP = Set Display Mode – Two choices, long display or short display

bDL = Alternator Failure Advisory – Two choices ON or OFF

 — = Advanced Programming – The gateway into advanced regulator Programming which features 15 customizable parameters

This second video examines the hierarchical menu of the MC-614 Regulator:

The third video show how to use Advanced Programming

TECH TIP: For batteries such as LiFePO4 you may find it necessary to reduce the bv setting below the default low of 14.1V. When using the regulators menu in scroll-order this is not possible because Av is set to 14.0V and each step must be 0.1V apart. There is however a work-around for this.

If  you wanted to set bv to  13.9V & Av to 13.8V you would need to reduce Fv first, then Av and then you can reduce bv. Each constant-voltage stage, bv, Av or Fv, needs to be programmed with a 0.1V spread. In other words bv can not be set lower than Av or Fv. The work-around is simple, just start backwards by reducing Fv first, then reduce Av then set bv last. Now you can drop the bv, Av & Fv target voltages lower than the factory defaults allow for.

bv = Bulk Target Voltage

Av = Absorption Voltage

Fv = Float Voltage

Confusion Creates Communication Issues

“RC I am fed up with this piece-o-crap alternator.It is in “bulk” and this damn thing is only putting out 20A. How can I send it in for repair?”

The above quote is a typical day in my world. Because the manual and charge lingo Balmar has chosen are confusing at best, trouble shooting time is burned up over perceived issues that are not real all due to semantics.

This all really boils down to two things.

1- Boaters generally understand that “bulk charging” means maximum output from the alternator.

2- Balmar calls a constant-voltage or voltage limited stage of charging “bulk voltage”.

Once voltage is maintained at a constant limit by the voltage regulator ACCEPTED CURRENT DECREASES. Once at constant voltage “bv – bulk voltage” the alternator is not at maximum output. The Balmar charging graph above, and on the right side, has been edited to show what really happens before we attain bv or “bulk voltage”.

Balmar only shows two things happening before constant voltage;

START DELAY

SOFT RAMP

In reality it’s really;

START DELAY – In this stage the regulator is applying 0% field to allow oil for circulation in the engine

SOFT RAMP – In this stage, a max of about 2 minutes, the field (regulator blue wire) is gradually ramped up to the maximum so as not to “slam” the engine with a huge load all at once.

*BULK CHARGING – During bulk charging the alternator is delivering everything it can, in current, to the battery bank. This can take as little as a few seconds for a bank already at high SOC or as long as multiple hours for a large bank deeply discharged.

*This is essentially an entire stage of charging (bulk stage) that Balmar left out of the graph. It is part of what leads to the confusion.

Understanding Battery Charging Lingo

The marine charging equipment industry apparently likes to keep customers “confused“, especially on topics surrounding battery charging. I suspect this is because it keeps the mystique of the “complex wizardry“, that goes on inside the product, a big secret?

In the marine industry almost all manufacturers use what is referred to as CC > CV charging, and this includes Balmar. The DIN standard designations for  charging would be I > Uo > U.

CC>CV charging simply means: Constant Current then Constant Voltage

Constant Current = The maximum current the charge source can deliver to the batteries

Constant Voltage = Voltage is held at a constant value by the regulation circuitry

In the rest of the world there’s actually a DIN standards that defines the charging process and it looks like this; I  Uo  U

I = Constant Current, CC, Bulk or sometimes called Boost Charging

Uo = CV/Constant Voltage, Constant Over Voltage, Absorption, Acceptance or sometimes Topping Charge

U = CV/Constant Voltage, Float, Finishing Charge or sometimes Maintenance Charge

It is important to note that under all definitions, whether DIN or the US terminology bulk charging is not governed by voltage being held steady, it is limited only by the charge sources output capability. During bulk charging, using real definitions, not made up definitions by a marketing department, voltage is always rising during bulk charging.

BULK = MAXIMUM CHARGE SOURCE OUTPUT WITH VOLTAGE RISING

“RC can an alternator really deliver a constant current?”

The answer to this is essentially no unless the alternator and RPM are held perfectly steady and the temp of the alternator stays the same. Despite myself and many others often referring to bulk charging, with an alternator, as “constant current” it’s probably better described as the alternators maximum current potential.

An alternator is affected by many things that a typical fixed-current battery charger is not. An alternator needs a maximum RPM to deliver it’s maximum current output. As an alternator heats up its winding’s lose efficiency and it’s current capabilities drop off a bit. This is why an alternator, or solar for that matter, is really better described as a maximum current potential charge source during bulk charging.

All maximum current potential means is that the alternator is being driven as hard as it can be, by the regulator, and it’s delivering its maximum current potential based on RPM and temperature. The alternators maximum current potential will vary up and down based on RPM, temp etc. however, it is still bulk charging and voltage will always be climbing towards the constant voltage limit. Because Balmar leaves bulk-charging off of their “stages” chart, and the description in the manual is a bit misleading, it can be quite confusing for the average DIY and even marine techs. Whether you choose to call it; bulk charging, maximum current potential, constant potential,  constant current or “I” it’s really just a matter of preference. In any of these scenarios voltage is ALWAYS RISING to the CONSTANT VOLTAGE limit. It’s far more simple to just call it bulk but some manufacturers have muddied those waters, including Balmar by calling a Constant-Voltage stage “Bulk Voltage”.  Perhaps a better and less confusing term for Balmar’s “Bulk Voltage” stage would be “Absorption 1”, but I digress….

Bottom Line? DURING BULK-CHARGING BATTERY VOLTAGE ALWAYS RISING!

IMAGE = BULK CHARGING: In this image we have a hot 110A small case alternator, held at a steady cruise RPM, and it’s delivering a steady 85A of output (red line). As we can see by looking at the blue line the battery voltage is steadily climbing from the 12.1V it started at (approx 50% SOC) and at the end of BULK-charging it has finally approached the regulators 14.7V Constant voltage limit or the Absorption or Uo stage where voltage will now be held steady by the voltage regulator.

Balmar regulators essentially have two absorption or Uo stages and they are called bV and Av. Balmar’s terminology for BULK CHARGING is “Soft Ramp“… Confused? You should be because it makes little sense based on industry accepted terminology.

Constant Voltage Charging

Now that we have gone over what bulk charging is, it’s also important to know what CV/Constant Voltage charging is.

Constant Voltage = Uo, U, Absorption, Acceptance, Float & Equalization

All of the above words are examples of voltage being held steady or a CV stage of charging. DIN separates Absorption from Float by designating absorption as Uo where the “U” means constant voltage and the  “o” means over voltage. The “o” in Uo just means that this CV stage (absorption) can not be held indefinitely or over-charging will result.

The Uo or absorption stage of charging (bv and Av for the Balmar regulators) is one of the most critical charge stages to battery cycle life. The job of the absorption stage is to bring the battery to full charge or very near and to reconvert the lead sulfate, created during discharge, back into active material. The DIN term “U” means Float and lacks the “o” because float can be held for longer periods with minimal risk of over charging.

US Lingo For Three Stage: CC/BULK > CV/ABSORPTION > CV/FLOAT

DIN Lingo for Three Stage: “I”/BULK > “Uo”/ABSORPTION > “U”/FLOAT

To simplify this even more try to consider a voltage regulator as  a VOLTAGE LIMITER. All a voltage regulator is really doing, during CV charging, is limiting to a preset voltage point, once the battery bank has attained the targeted voltage.

IMAGE = ABSORPTION CHARGING: This graph is just a continuation of the charge process started in the previous image. To the left we can see the current still steady at 85A (max alternator current output) but the voltage is climbing up to the pre-programmed voltage limit of 14.7V.

Once the battery bank has attained the voltage limit, in this case 14.7V, the regulator switches / transitions from bulk/max current potential to constant voltage charging where the voltage limit of 14.7V is now held steady by the VR. The voltage regulator is now doing it’s job as a “voltage limiter” instead of just driving the alternator to its maximum potential output.

In the graph you’ll notice that once voltage is held steady the current begins declining. This current decline is simply the result of the relationship between terminal voltage, current & SOC (state of charge). In order for the regulator to hold voltage steady, with a climbing SOC, the current being fed to the battery has to decline or the voltage set point would be over-shot. During absorption charging (bv or Av) the battery is dictating what the current can be so as not to “over-shoot” the 14.7V limit. As the SOC of the battery increases less and less current is needed to not over-shoot the voltage limit.

Key Points:

#1 During bulk charging the amount of current available to a the bank determines the bulk duration.

*High Charge Current = Shorter bulk duration and a CC to CV transition point at a lower state of charge

**Low Charge Current = Longer bulk duration and a CC to CV transition at a higher state of charge

*A Lifeline AGM Battery bank charged at 40% of Ah Capacity (160A for a 400Ah bank) will be bulk charging for around 20 minutes. This means the maximum bulk duration is pretty short, the alternator is only at max potential for about 20 minutes and the rest is CV charging where current is steadily declining.

**If we cut the above charge current in half, and charge the same bank at 20% of Ah capacity (80A for a 400Ah bank), the bulk charging duration lasts about an hour and fifteen minutes. Asking any small-frame/small-case alternator to produce its maximum output for 1:15 is pretty tough and it will develop tremendous heat. This is why Balmar offers Belt Load Manager and an alternator temp sensor. Please use them if you have a large or high acceptance bank.

#2 During absorption/CV charging it is the battery that determines the time it takes to get to 100% SOC. The only way to change this relationship would be to increase the target voltage but most batteries have a reasonable limit as to the maximum target absorption voltage.

Programming Tips to Maximize Your Investment

IMAGE: This image is from a reputable deep cycle battery manufacturer and shows their suggested charge voltages for a 12V battery. The 12V battery at 77F  is highlighted by the blue arrows. Also note the temp compensation they show in this grid. The temp compensation for this brand is all based on a 5mV compensation (per cell) for each 1°C change in battery temp. If your battery manufacturer can’t provide this information, walk away.

Are you charging your deep-cycle batteries at the optimal voltages for a long cycle-life?

The Balmar regulator is an excellent tool for battery charging but sadly far to many of these regulators are not programmed to work as effectively as they can. These tech-tips can help.

TECH TIPS:

1- Small-Frame Alternators are Not Constant Duty – If you have a small frame alternator and a large bank please use Belt Load Manager AND an alternator temp sensor. Your alternator will last much longer when not pushed to it’s maximum every time it is used.

2- Setting Only bA / Battery Type is Inadequate Programming – Setting a base battery type, and walking away, is about as useless as buying a Bugatti Veyron Super Sport and then installing some 1940’s bias-ply whitewall tires.  You’re simply not getting your money’s worth out of the regulator by doing this.

3-  Use Alternator & Battery Temp Sensors – These regulators are not complete until you install the alternator temp sensor MC-TS-A, and the MC-TS-B battery temp sensors. Unless you bank is very small, in relation to the alternator, then an MC-TS-A will be a necessary insurance policy. Every battery manufacturer on the planet prefers temperature compensated battery charging, and most reputable manufactures require it. A Trojan battery that charges at 14.8V at 77F – 80F can not charge at 14.8V at 95F. Without a battery temp sensor you run a much higher risk of cooking your battery and causing accelerated plate erosion.

Battery temp Compensation Slope Adjustments: The battery temp compensation feature on the Balmar regulators is adjusted using the SLP or SLOPE feature  in the advanced programming menu. This allows the regulator to be programmed for exactly the temp correction the battery maker specifies. One area where folks often get confused is in thinking it is only adjustable from 0-8.3 mV per battery. The 0-8.3 mV is per cell and for a 12V regulator this is 6 cells.

In other-words the regulator setting is adjusting temp compensation slope on a per cell basis, in degrees Celsius, not based on 6 cells or a whole battery. If a battery manufacturer wants 0.002 mV per-cell, per-degree C, this would be 0.012V per battery, per degree C change, but the regulator would be set to 0.002 for slope per cell and would compensate the battery at 0.012 mV per degree C change because it knows it is a 12V regulator and automatically multiplies your setting based on 6 cells.

4- Avoid Premature Float – Setting an adequate absorption/CV duration, (time spent at constant voltage), is critically important to battery health. The factory settings of 18 minutes for bv and 18 min Av plus any “calculated” additional time are not going to help you get the most from these regulators. In a perfect world the “calculations” that can extend or shorten the CV time calculations would work perfectly, unfortunately they rarely do, and this is why there is an advanced programming menu. B1C (bv duration) and A1C (Av duration) can be extended or shortened in the advanced programming, and should be in almost every installation other than LiFePO4.

The algorithm for bv and Av works like this: Programmed time completed/elapsed, regulator field percentage below 65% (or what ever you’ve set it too), voltage has been stable for 2 minutes. Once these three criteria have been met the regulator can now move to the next stage. Please bear in mind that the alternator has NO CLUE what percentage of the field is being used to power on-board loads or to charge the battery! This is exactly why you will need to custom program it so you are getting your money’s worth.

As noted above B1C and A1C time settings, % field and voltage stability (why correctly wired volt sensing is critical) must be achieved before the regulator can move to the next stage, and this is most often a good thing. The factory “base battery type” settings allows for the regulator to drop to float far too early, and I say this with nearly 30 years of experience with these regulators as well as using them as teh default regulator on our alternator testing machine here at Compass Marine Inc… Unless you routinely motor for 6+ hours, when out cruising, you should rarely, if ever, see your regulator drop to float. If it is doing this, you can fix this in the advanced settings menu by extending the minimums on the B1C or A1C time clocks and / or adjusting the field percentages that allow a transition. The only parameter that cannot be changed is the voltage stability the reg is also looking for.

I will often set bv at 0.1V over max factory recommended absorption voltage for 6-18 minutes, depending upon battery type, then set Av to the maximum allowable absorption voltage for anywhere from 2 hours to as much as 5+ hours depending upon the bank and available charge current.

On 3/21/18 I capacity tested a 2014 100Ah TPPL AGM battery that has been charged “properly“. Properly defined as a minimum of .4C in charge current (40A for a 100Ah battery) per manufacturer minimum current guidelines. Bulk-voltage bv is set to 14.8V bv for 12 minutes, then to 14.7V Av for 5 hours. This is 5:18 at constant voltage, temp compensated and an alternator float of 13.8V. The other charging equipment on the boat is solar, set similarly but a 2 hour absorption vs. 5 hours (due to the low current), and with float set to 13.4V.

The battery delivered 96.54Ah out of it’s 100Ah rating. A month earlier I tested a 2016 version of the identical battery. It had been charged only by a stock Hitachi alternator only. It delivered 56.83 Ah’s. The correct absorption voltage and a long enough absorption duration matter and can make big differences in bank longevity.

Yes, the Balmar regulators “try” to maximize and deliver a correct constant voltage duration but, in most cases, they fall short and drop to float far too early. The reason for this is simple, all the regulator knows is voltage and % of field drive. Voltage is simple, but the % of field drive actually being used to charge the batteries is nothing more than a crap-shoot guess for the regulator. What I mean by this is the regulator only knows a voltage, as sensed by regulator + sense and regulator B-, and the percentage of field output. What if 60% of that field output was being used for a water-maker, refrigeration, inverter, or other house loads? What if there were no house loads on at all? What if they turn on and off throughout the charge cycle? You can spend lots of time messing with field percentages but they change and you may not be happy with the results.. The easiest way around premature float is to extend the constant voltage time parameters in either b1c or A1c.

“So what’s the bottom line?”

If your regulator is dropping to float before the batteries are accepting less than 1% – 2% of Ah capacity, at ABSORPTION voltage (NOT float) then it is dropping to float too early. Most AGM’s are between 0.5% of Ah capacity (Lifeline) and 0.3% (Odyssey, East Penn/ Deka etc.) of Ah capacity to use tail current as when to drop to float.. Control this via b1C or A1c or field percentages, if you decide to experiment with field percentage. Extending the A1c duration is generally the easiest method.

Charging Batteries Correctly is Critical

5 – Set Yourself Up For PSOC Success – Using the highest absorption voltage the battery maker allows for will result in the least PSOC (Partial State of Charge) damage to the battery. Even the fastest charging AGM batteries require approximately 5.5+ hours to go from 50% DOD to 100% SOC, and this is in lab conditions with no chance of premature float and with 20% to 40% of Ah capacity in charging current. Flooded & GEL batteries charge even slower so absorption times will need to be adjusted to suit the batteries. The worst efficiencies for charging are from 85% SOC to 100% SOC and this duration alone, the last 15%, even with AGM batteries, often takes 3 – 6+ hours depending upon battery state of health. In the ideal set up your batteries don’t drop to float until they are 100% full. With voltage regulated charging this is tough but we can certainly do better because the MC-614 and ARS-5 regulators can be programmed eight ways from Sunday with ample opportunity to minimize premature-floatulation.

6 – Over Charging Concerns – If you’re concerned about “over-charging” when you leave the dock “fully charged“, which is really more of a personal problem rather than a real problem, simply install a dash switch that interrupts the regulators brown wire or ignition feed to shut it down. If you want to further complicate a relative non-issue you can use a resistor in the battery-temp compensation circuit to trick the regulator into a lower voltage by making it think the battery is hot. I call this trick “switch triggered float”..

I’ve autopsied piles and piles of batteries, both sealed and non-sealed, and the number of “dried-out” VRLA batteries (GEL or AGM) I have seen have been an n=2 banks. Both of these banks were ruined by controller-less solar systems (no charge controller at all) pushing 15+V every day. These batteries were not ruined by voltage regulated alternators leaving the dock at 100% SOC. By far and away the biggest concern with marine batteries is chronic under charging. The Balmar regulators can be programmed to help you avoid this.

7- Utilize Balmar’s Advanced Programming Menu – If you’re not taking advantage of the advanced programming features, ones you’ve actually paid for,  you’re really only seeing a marginal, if any, gain in actual charging performance.

8- Wire the Voltage Regulator Correctly – I hear lots of belly-aching over short bulk charging. In every single case of this I find the voltage sensing circuit wired INCORRECTLY. In regards to charging performance, even the Balmar manual is incorrect on how to properly wire voltage sensing. This article cannot be over-looked: Alternators and Voltage Sensing – Why it Matters

9- Field % Transition Thresholds – For a DIY, with not a lot of electrical experience, I generally advise extending b1c and A1c time clocks and leaving the Field Percent Transition Thresholds, FbA (Bulk to absorption) and FFL (from float back to absorption) alone. However, please don’t take this as a blanket statement and don’t be afraid to experiment with the field transition percentages. They are easy to re-set to the factory default, if what you changed does not work.

The difficulty with field percentage transition thresholds is the regulator has no idea what percentage of the field is being used for charging the batteries and what percent of field is being used to power on-board house loads. It is, after-all, a voltage regulator not a current regulator. If your house loads are very predictable, you can easily get the field transitions to work well, but it may take some experimenting and time to dial it in just right. If you run large inverters while under way or have unpredictable loads, while charging, it may be tougher, but please don’t be afraid to experiment with it.

10- It’s All About the Correct Voltages – For years the flooded deep cycle battery industry was stuck in the dark ages as to how to correctly charge lead acid batteries that were used in a PSOC environment. This is because industry and stationary systems require slightly different charge profiles than do PSOC use situations. Today, thanks to folks like Tom Hund (retired), of Sandia National Laboratories Photovoltaic Department, we now know that in order to correctly charge deep cycle flooded batteries we need significantly more terminal voltage during absorption than the antiquated 14.1V to 14.4V old-school guidance used to suggest.

Sadly no-one has keyed in the majority marine charge equipment manufacturer’s about this “breakthrough” information. In their defense, we’ve only known this for 20 or so years. (grin) With a Balmar regulator you can program to your hearts content and get it right.

If you’re not charging deep-cycle flooded batteries at 14.6V (bare minimum) to 15.0V, for PSoC use (boats, RV’s or off-grid solar), they’re simply not getting properly charged. Even many AGM batteries are capable of being charged as high as 14.7V and their health is vastly improved by doing so. With all that said, use your battery manufactures recommended voltages but stick to the maximum of the safe-range not the low side. For example if your battery maker suggests an absorption setting of 14.4V to 14.8V you’ll want to be at 14.8V end of the spectrum not at the 14.4V end.

Proper Programming, It’s Your Choice

IMAGE: Pictured here is a typical automotive voltage regulator the type found on most marine engines as they ship from the factory. I busted it open and extracted all the potting material so you could see the difference. With this image it is easy to understand why an external regulator, with all the features the Balmar’s offer, can lead to better and healthier charging for deeply cycle batteries and to better protection for the hard working alternator.

In the end it is your boat, and you’ll need to decide how you want to program your regulator, for your own piece of mind. All I can say, as a marine energy management specialist, is that I find far too many external regulators inadequately programmed & wired for the owners to be “getting their money’s worth”. Get your money’s worth and venture into the advanced settings!

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A Deep Cycle Battery Assassin

The alternator pictured here helped to destroy a very expensive bank of TPPL AGM batteries in under two years. These batteries need an absorption voltage of 14.7V. The highest voltage I recorded on this vessel was 13.58V at the battery terminals. At this rate it would have taken days not hours to fully charge these batteries. Both voltage drop and a “thermistor” auto type alternator were to blame.

Internal automotive type voltage regulators are one of the most often misunderstood devices out there. They are simple but they also vary quite a bit in how they regulate or limit voltage. All a voltage regulator does is limit voltage but some go a step further and try to protect the battery or protect the alternator itself.

Just because an alternator comes standard on a marine engine does not mean it is a marine duty or high performance alternator. In most every case these alternators are nothing more than a light duty automotive alternator slapped onto a marine engine.

Unfortunately, for boaters, automotive batteries are vastly different in the way they need to charge, when compared to a deeply-cycled marine battery bank. The auto battery sits in a hot engine bay, think summer time stop & go traffic, and the alternator is in there too. The auto industry and battery makers know that heat is a prime assassin of batteries. If the charge voltage is not compensated for when the batteries are hot they can become dangerously over charged.

In order to address these issues, in a rather Band-Aid like fashion, alternator manufacturers such as Hitachi, Mitsubishi, Denso, Delco, Paris Rhone/Valeo etc., etc. began adding a simple thermistor to the voltage regulation circuits as automobile load demands went up throughout the 70’s, 80’s and 90’s. The internal thermistor causes the regulators target voltage to decrease, as the alternator temp increases. The Hitachi/Yanmar voltage reduction is one of the most severe I’ve measured.

Unfortunately these reductions in the regulation limit voltage occur based on alternator or ambient alternator temperature regardless of whether the alternator is too hot from being over worked or not. Take for example a small engine bay on a typical sailboat, it is not uncommon to measure engine room temps of 145°F or more.

If we assume 145°F with a typical Yanmar / Hitachi alternator, based on the thermistor temp gradient built into the regulation circuit, we can see that at 68°F it should produce 14.4V +/- 0.3V (BTW +/- 0.3V is horribly SLOPPY). However, for every degree rise above 20°C/68°F, it reduces the regulation voltage limit by -.01V per degree Celsius. An engine bay temp of 145°F correlates to 63°C. An ambient temp of 63°C is a temp increase of 43° Celsius beyond the thermistors baseline of 20°C / 68°F.

43° X .01V = -.43V

With just an engine room temp of 145°F the highest regulation voltage we can attain is 13.97V. Keep in mind I have not even included for any heat generated by the alternator itself here, just the engine room temp.

This Band-Aid approach is marginally acceptable for an automotive battery, which is accepting a few amps of charge current in a 130°F engine space, but absolutely horrible for a deep cycled battery at 70°F accepting more current than the alternator can produce, while trying to get to a proper and healthy absorption voltage.

In an automotive application this feature serves to protect the battery, but in a marine application it serves to protect the alternator, (reducing charge voltage reduces accepted current the battery can take) but then serves to murder the batteries. Not all marine alternators use thermistor limited regulation circuits but more and more do as the years go on. Alternators such as the Motrolola style units on early Westerbeke and Universal engines, or the Leece-Neville 8MR series have simple “dumb regulators”.

Lets examine at some of the crude definitions often applied to factory (automotive) alternators:

Dumb-Regulated – A simple dumb regulated alternator does BULK and ABSORPTION and that is it. There is no thermistor protection for over heating or battery temp compensation and they do “burn-up“, quite frequently, when used to charge large battery banks. If the voltage regulation point is 14.4V it will bring the bank to 14.4V and simply hold it there. If the regulator senses that it’s below 14.4V the alternator is in BULK mode putting out all the current it can based on rotor RPM and copper temperature. A healthy and long absorption charge is actually good for deeply cycled marine batteries and is the part of charging that serves to reconvert lead sulfate.

Super-Dumb-Regulated – Basically the same as above but they have an additional thermistor self-protection feature that reduces alternator regulation voltage based on alternators ambient temperature. These alternators are a poor match for deeply cycled batteries because they chronically under charge them, especially with the short duration engine run times sailors prefer when out cruising. When you reduce the voltage limit of the alternator you also greatly extend charging times. Voltage is the pressure that allows current to flow into the battery, low voltage = lower current and considerably slower charging.

Lowering the regulation voltage limit has the net outcome of reducing current output thus allowing the alternator to now cool off a bit and hopefully not cook itself. Thermistor type alternators are just basic inexpensive automotive alternators. Reducing voltage using a temp gradient is the least expensive way to get these alternators through the warranty period and not destroy hot automotive batteries in a few months. As applied to the marine market the alternator maker could care less about your batteries or how fast you destroy them, they only care about making it through the warranty period.

Certainly with 20+ hour motor runs, which are about as rare as fish with legs, getting back to 98-100% SOC is possible even with a “Super-Dumb” alternator regulator but this is many, many, many hours longer than it would take with a simple dumb-regulator or with an external smart-regulator set up correctly.

What about external regulation?

Smart Regulation – Smart-regulators handle the alternator a bit differently, in terms of protecting the alternator or reducing terminal voltage, to temp compensate the battery. Balmar and some other smart regulators, reduce the field voltage, which in turn reduces alternator current output. They can do this based on a high-limit for alternator temperature while still keeping the voltage limit set point exactly the same. The smart regulator does not begin reducing field voltage UNTIL the alternator hits the high-limit.

For example, the current output of a 100A alternator may be reduced to just 70A, to keep it below 230°F, but the pre-set voltage limit still remains at 14.4V – 14.8V, or where ever you set it at for your particular batteries. By temp protecting the alternator it does take slightly longer to get to the designed target voltage, but the target voltage has not changed or been reduced based on ambient engine room temps and the alternator is still climbing towards that voltage at the maximum safe temp it can do so. The only change in regulation voltage is that the time to get to the limit voltage is slightly extended so as not to cook the alternator.

Important: Not all external voltage regulators are created equal in regards to alternator temperature protection. The Wakespeed WS500 regulators utilize an “predictive” alternator temp sensing algorithm that can “predict” where the alternator temp is going based on rate of temperature rise. This means the WS500 can run the alternator to within a 2-4 degree window of the alternators safe temp. In other words the WS500 can extract the maximum current that is safe for the alternator at all times. No other regulator can do this.

Other external regulators cut the field by 50% or 100%, wait for the alt to cool, and then go back to 100% output. This results in a ping-pong match between the regulator and alternator that looks like this.

100% > 0% > 100% > 0% > 100% > 0%

or

100% > 50% > 100% > 50% > 100% > 50%

Because the WS500 regulator is always seeking the maximum safe running temp of the alternator it yields the best continuous output performance. Expensive? Perhaps, but you really do get what you pay for.

Contrast how a WS500 regulator maximizes alternator output to a stock Yanmar / Hitachi alternator which reduces the regulation voltage limit/target based on ambient alternator temp, and there is no comparison in terms of charging performance. With smart-regulators the voltage limit is not reduced, just current output via the voltage applied to the brushes is reduced. Reducing current output slows charging a bit but nowhere as much as reducing the limit voltage based on ambient alternator or engine room temp. While reducing the current output does extend bulk charging time you still get a healthy absorption stage and you still get to the target voltage significantly faster. This type of regulation is more expensive and thus why cheap automotive type alternators don’t use it.

How is This So?

This image is a typical spec sheet for a Yanmar/Hitachi alt:

The regulation voltage is specified at +/- 0.3V which, in and of itself is pretty pathetic, but this is what you get from a $6.25 regulator. If the design voltage is for 14.4V then this means you could possibly get one at 14.1V or one at 14.7V. Kind of a luck of the draw of specification. D’oh..

Of course the regulation voltage limit only tells part of the story. You then need to subtract a voltage gradient caused by the thermistor, of -0.01V for every degree rise in Celsius above a 20°C baseline, which is 68°F (see red arrow & red box in image). If the alternators set point was 14.4v by the time the alternator gets to 200°F the limit voltage has been reduced to just 13.67V and this does not even consider any voltage drop in the system wiring between the back of the alternator and the battery bank. It is not at all uncommon to see an alternator charging large deep cycle banks at 225°F – 230°F so 200°F is actually being kind.

Want to make this debacle even worse?  Imagine for a minute that somewhere along the way the PO or boatyard installed a diode isolator in the path of an automotive grade alternator. On top of the already low output voltage you now have an additional  -0.6V to -1V drop in the alternators path. I have seen and measured 80A factory alternators barely able to deliver 10 or 12 amps to the batteries in what should be “bulk” charging. Low voltage at the battery terminals = low amperage output. Ouch!!

Proper Absorption Voltages:

The absorption stage and absorption voltage set point or limit are critically important to maintaining healthy batteries. Attaining the proper voltage and then keeping it at the desired set point, for the proper duration, means faster & healthier overall charging.  Thermistor type alternators rarely if ever reach the proper absorption voltage, on deep-cycling banks. If they can’t even get to the proper absorption voltage, due to heat, then holding these voltages for the correct duration is simply a pipe dream. The correct absorption voltage and absorption duration are one of the most important aspects of deep cycle battery charging.

The reason the Yanmar/Hitachi alternators charge so slowly, and you rarely see anywhere close to rated output, except for a few minutes after a cold start, is because the regulator in them is actually not suitable for charging deep-cycling banks.

If you want to protect an alternator, to make it through the warranty period, reducing regulation voltage can work okay. If you actually want to charge batteries, used in deep cycling applications, and do so in a healthy manner, alternators with internal thermistor regulation are really quite pathetic.

In a marine application the regulator inside them is only about one thing, protecting the alternator from melt downs. It’s not about charging performance nor does it care about your batteries. Slap it in a car, where the batteries are always full, and you’re good to go. Put it in a boat with deeply cycled banks and they really perform horribly.

Cooked…!!

Just because an alternator regulator has a thermistor in it does not mean it will always protect your alternator from cooking itself. This alternator was charging a large bank of flooded batteries, almost 900Ah. It got so hot that it had cooked the stator as well as melting the seal out of the front bearing. An external regulator with alternator temp protection could have saved this customer from an expensive repair where even the thermistor regulation circuit could not.

If you want to protect an alternator, to make it through the warranty period, reducing regulation voltage can often work okay, but it did not here. If you actually want to charge batteries, used in deep cycling applications, and do so in a healthy manner, alternators with internal thermistor regulation are really quite a poor choice.

New vs. Fried

In case the context of the last photo was lost, this is a new stator and a fried stator. This alt was also thermistor protected but the battery bank was simply too large, and regularly over discharged, for the alternator to adequately self protect itself. In this case a properly installed external regulator with an alternator temp sensor, would have saved this alternator.

Voltage Profile – Temp Protected Auto Alternator

So what does the charge voltage actually look like with a thermistor protected alt charging a deep cycle house bank? It looks something like this.

This alternator was 80A rated feeding a 400Ah bank. In just 13 minutes the alternator was surpassing 225F (Fluke 289 with temp probe). At that point voltage stopped climbing and became somewhat steady. Once voltage was held steady the amperage output started to decrease slightly thus allowing some cooling of the alternator. About 18 minutes later the voltage rose to just under 13.7V but the alt temp had increased again so it continued to bounce along somewhere between 13.64V and 13.69V.

I data logged this voltage for 1.5 hours and it never exceeded 13.81V. Needless to say the batteries were getting chronically under charged and charging extremely slowly.

Voltage is the pressure that allows current to flow into the batteries and without a sufficient charge voltage only so much current will flow into the battery. This of course is based on its state of charge, internal resistance and actual terminal voltage. By reducing the terminal voltage you also reduce how much current the battery can accept.

The mooring sailed boat I created this graph from destroyed a set of AGM batteries, using a Hitachi internally regulated alternator, in just 18 months. Ouch, expensive mistake. The owner blamed it on the AGM’s when in fact the AGM’s would have been fine had they been properly charged.

Voltage Profile – Smart Regulator

This boat has a large bank of Trojan flooded batteries and the alternator, with smart regulator, is sized at 20% of the banks Ah capacity (cold rating). With the smart regulator it took approx 75 minutes, at full output (though temp protected), of continually rising voltage during bulk, for the batteries to attain the absorption voltage limit of 14.8V. Once at 14.8V the voltage was held steady by the regulator while current began to decrease. By sizing your alternator to 20-25% of the banks capacity, using its hot rating, your can rather drastically reduce the bulk charge time.

This is what a healthy charge voltage profile looks like. The other bank, previously shown, never exceeded 13.81V in 1.5 hours yet this bank attained 14.8V at 75 minutes and then continued to hold the proper absorption voltage for these Trojan Batteries. These batteries were in their 8th year.

Do I Really Need a High Performance Alternator?

Large Banks:

Pictured above is a Balmar AT Series “small case” alternator. This one uses Denso licensed hairpin stator / rotor design. For a small case alternator it was a very good performing alternator. Balmar has since re-designed its highest performing small frame alternator with the new Balmar XT-170.

Because most sailboat auxiliary engines use small-frame alternators, owners are often limited in amperage from 80A to around 175A. Anything over 100A will require a serpentine or a dual-v belt system. Still, an externally regulated 80A alternator will run circles around an 80A internally regulated alternator in terms of  healthy charging performance.

When ever possible, when charging large Ah banks, it is best to try and fit a large frame alternator designed specifically for a heavy duty applications. Small case alternators, even “high performance” models, despite what many folks think, are not constant duty rated, not even the Balmar XT series is “constant duty”. If your bulk charging will be longer than about 30 minutes even a Balmar XT will need to be current limited, via the external regulator, to make it last.

Medium Banks:

Other options for higher performance small case alternators would include the Balmar 6-Series alternators. The 6-Series alternators are a bit less expensive than the Balmar XT series and are suitable for many medium sized banks, and even larger banks, with a properly current limited external regulator such as a Balmar ARS-5 or MC-614..

Small Banks:

For a bank in the 150Ah to 400Ah range you may not need the performance of a Balmar XT or a 6-Series alternator. To fill this niche Compass Marine Inc. has developed the cost effective, Yanmar fit,  CMI-80-ER. There are many others too: MHT Alternators & Regulators

What you need for an alternator will depend entirely on your actual use and battery bank chemistry. Despite everything I have just written above, the answer may actually be;

No, you may not need a high-output alternator.

What you need will depend largely on use, bank size and desired daily Ah consumption as well as battery chemistry type. You will also need to consider your maximum desired engine run time. If you only day sail, and tie to the dock every night with shore power charging, converting the factory alternator, to a higher performance model, will gain you little. This is why; it’s all about use.

What should I do if I have a….?

Dumb Regulator With Low Voltage Set Point – If you have an old 13.6V – 13.8V regulator, and wet cells, ditch it and get a regulator that is a minimum of 14.2V – 14.4V or even 14.6V and you will charge a lot faster. Battery gassing generally begins above 14.3 volts, though is temp dependent, so a dumb reg that does 14.5V – 14.6V will cause your batteries to need water added more often. 14.4V would be better maintenance wise but 14.6V will charge even faster and is arguably going to fend of sulfation better. If you are a coastal cruiser doing 40 engine hours per year this is a perfectly adequate option. Best case here is to convert the stock alternator it to external regulation or consider one of the entry level externally regulated alternators offered by Compass Marine Inc..

MarineHowTo.Com – Alternators & Regulators

Dumb Regulator – (Non-thermistor model) This can do marginally well provided you have flooded batteries, minimal voltage drop in the system and it regulates to around 14.4V or so. It should match closely to the specified absorption set point of your batteries. While a single absorption voltage is arguably less than ideal, if you are not a full time cruiser, and tie to the dock regularly, an arrangement like this can suffice. Be aware that with a medium to large bank you can very easily burn up a “dumb-regulated” alternator, if you discharge too deeply.

Super-Dumb Regulator – (thermistor compensated) If you tie to a dock after each sail and put the vessel on a  shore charger, you can probably keep this alternator. If you actually cruise regularly, & deeply cycle the batteries, do yourself a favor and convert it to external regulation or upgrade to a higher performance alternator & regulator.

Voltage Sensing Improvements:

Stacked on top of the voltage gradient issues, stock alternators also suffer horribly from voltage-drop between the alternator and the battery bank. Some stock alternators can be set up or wired to provide better external voltage sensing, at the battery terminals, as opposed to the back of the alternator itself. Please do not try this if you don’t know what you are doing. Any good alternator shop can help you with this and it can make a difference in charging performance. The only way to get accurate voltage sensing is for the negative regulator lead and the positive sense lead to be direct wired to the battery bank. This is not always possible with factory alternators and you only typically get a positive volt sense lead to work with. For more information on the role accurate alternator sensing makes to performance please read:

Alternators & Voltage Sensing (LINK)

How do I Measure the Voltage Set Point/Limit of My Existing Regulator?

• Make sure the batteries are at 100% state of charge
• Make sure the alternator & engine room are cold/ambient temp
• Turn off all DC loads & charge sources including solar
• Start the engine and using a DVM test the voltage at the alternators B+/Output terminal & B- or case of the alternator
• Wait for voltage to stabilize
• Voltage should be somewhere around *14.2V & *14.4V

*Many regulators on Universal engines were factory set at 15.0V to try and compensate for the horrible factory wiring. Many Delco regualtors are also as high as 14.8V – 15.0V. I do not recommend using single point voltages, with this high of a voltage set point especially when charging into full batteries such after leaving a dock after being on shore charging.

When do I Need a High Performance Alternator & Regulator?

Did I over Think My System?

In my opinion, a lot of coastal & weekend only boaters, with inexpensive automotive type G-24, 27 & 31 flooded batteries, who are tied to shore charging all week, can & do sometimes over think and over blow charging systems. There is nothing wrong with this, it is not at all going to harm anything, so long as your wallet can handle the punch.

What Battery Chemistry Do You Have?

With certain battery types though you really do need to design and install a proper alternator based charging system. The reality for us here at Compass Marine Inc. is that we see less than 35% of the boats out there using AGM, GEL or AGM TPPL batteries, yet nearly 50% of the coastal/weekend cruisers have a fully gourmet 1.5K+ alternator charging systems. Many who are dockside most of the time and as a result have no dire need for a system this fancy. Money wasted? Some times yes, when based on actual use. Like anything, be realistic about your usage. Bottom line? If you’ve spend good money on AGM, TPPL AGM, GEL or LiFePO4 batteries then yes, you do need a proper alternator charging system!

When Should I Use External Regulation?

Flooded Cell Batteries – If the bank exceeds the hot rated alternator capacity by more than 80% I recommend a smart regulator & temp sensing of both the battery bank and alternator. Eg; a 400 Ah flooded bank is comfortable with about 100 amps in bulk so a 70 amp alternator, using its hot rating, would get external regulation with alternator temp sensing at the least.

TIP: We generally recommend installing an alternator that is one or two size larger, than is desired in output, & then derate the max current output in the regulator. This allows the alternator to work less hard , run cooler & live a longer life. This can be done with Balmar regulators by using the Belt Load Manager feature.

AGM Batteries – I always recommend external regulation with alternator and battery temp sensing at a minimum. I have seen a number of dumb & super-dumb regulated alternators burned up by the high acceptance rates of AGM batteries. On battery temp compensation is a minimum requirement for all AGM batteries, and factory alternators don’t do this correctly.

GEL Batteries – I always use external regulation with alternator and battery temp sensing at a minimum. GEL’s require specific voltage ranges that dumb regulators just can’t accommodate very often. On battery temp compensation is a must have with GEL batteries.

TPPL AGM Batteries – Same as AGM except that some TPPL AGM batteries want to see a minimum charge current (MINIMUM not maximum) of 40% of rated Ah capacity or a 160A alternator for a 400Ah bank (hot rated output not cold). Charging at less than 40% of Ah capacity can negatively impact the cycle life of TPPL AGM batteries. At a bare minimum you want to be hitting these batteries with 30% of Ah capacity or more in bulk charging current.

Dumb Regulator / Temp Compensated (Hitachi/Yanmar etc.) – These factory alternator regulators are horrible for deep-cycling applications. Almost every Yanmar engine with a Hitachi alternator, if used regularly in a deep cycling application, should be converted to external regulation or convert to a new alternator & regulator.

Dumb Regulator / Low Voltage Set Point – If your alternator regulator is set to less than 14.2V it would be wise to invest in a better regulator.

Inaccurate Voltage Sensing – This piece of the charging puzzle can not be over looked. Many factory systems have horrendous voltage drop between the battery bank and alternator. These alternators are what is commonly referred to as self-sensed meaning they measure system voltage at the alternator BEFORE ANY VOLTAGE DROP has even occurred. This will cause the alternator to go into the absorption/CV (constant voltage)/ voltage limiting stage prematurely. External regulators correct for this by allowing positive and negative regulator wires (volt sensing) to be routed directly to the battery terminals. This can yield significant increases in charging performance. For more info on this see: Alternators & Voltage Sensing (LINK)

A Stock Leece-Neville 8MR Alternator

Many boats, both power and sail, come equipped with, or have have used, the 5″ small-case Motorola/Prestolite/Leece-Neville style alternator. There are literally thousands of these alternators out there. Even large Caterpillar and Cummins engines have used the 8MR alternators.

This Motorola style alternator is currently being manufactured by Leece-Neville and they are a darn good small frame alternator, for their size. Be careful however as there are many shifty / shady on-line retailers selling clone 8MR’s that are not genuine Leece-Neville and they are nowhere near the quality. If you intend to use one of these on a boat please use only a genuine Leece-Neville product. The 8MR series, pictured here, is specifically marinized to meet USCG & ABYC ignition protection standards. After you convert it to external regulation you technically lose this “USCG certification” but the same gasket, the part that makes it ignition protected, is used in the external regulation kit.

NOTE: Leece-Neville 8MR alternators do not ship with pulleys or the 1″ to 2″ fit kits that make them work with most marine engines. Because these alternators use an odd-ball shaft size, we are custom machining, out of billet steel, both 3/8″ and 1/2″ single v-pulleys so you can build a complete alternator.

Accessories needed in addition to the alternator:

CMI 3/8″ Belt, Single V, Billet Machined Pulley

CMI 1/2″ Belt, Single V, Billet Machined Pulley

CMI 1″ to 2″ Fit-Kit

8MR External Regulation Kit (Discontinued Part – No Longer Available)

The 8MR series is available from 37A to 105A & available in a 2″ single foot or a 1″ single foot. Some models are a single adjuster ear and others come with a universal ear configuration. The regulators though are all the same old design. While many modern alternators including Denso, Delco, Valeo, Mitsubishi, Hitachi, Paris-Rhone, Bosch etc., use an internal thermistor circuit to reduce voltage as the alternator heats up, for self preservation, the 8MR series does not. Install these alternators on a large enough bank and they will literally cook themselves.

The voltage regulator, that comes equipped on certain new 8MR series alternators, feature an adjustable voltage but they are still only single-stage (really a two stage BULK & ABSORPTION) not a three stage regulator with no temp protection at all. The stock internal regulator lacks temp protection, float modes and a myriad of other features external smart-regulators can offer. This regulator has an adjustable output range from 13.8 – 14.6 V. They ships from the factory set at 14.2V.

In this article we’ll show you how to convert a Motorola/Leece-Neville 8MR style alternator to external voltage regulation. Once you’ve done this conversion you can then use a Balmar, Wake-Speed or other external smart regulator.

Our favorite external smart regulators are the Balmar regulators. Why? Because Balmar offers more features and programming options than any other regulator on the market at that price point. They also have excellent tech support and answer the phone using human beings.

The Xantrex XAR regulator was also made by Balmar for Xantrex, but it has been discontinued. We suggest sticking with Balmar. You get what you pay for with a Balmar regulator and the MC-614 is our hands down favorite.

This particular alternator is a 90A Leece-Neville 8MR2070TA. It features a 1″ foot and universal adjusting ear. It fits most Universal and Westerbeke engines (except those that use a a dual-foot 50A Mitsubishi alternator) as well as many others.

Remove These Four Screws

The first step in this conversion is to remove the four machine screws holding the stock-regulator onto the alternator. They are pictured here loose so it’s easy to see which ones they are.

Flip The Regulator Over

The next step is to remove the four wires that connect the voltage regulator to the alternator. For the 8MR-2070-TA this means one red wire, two yellow wires and one black wire. This is as easy and as straight forward as it sounds.

Once the wires have been disconnected simply tilt the regulator up to expose the internal brush connections. You’ll need a set of needle nose pliers to pull the connectors off the brushes. This is quite simple and takes about 20-30 seconds to complete.

Spark Arrestor Gasket

This gasket is what makes the factory 8MR ABYC & USCG compliant for ignition protection.

This gasket prevents errant sparks from the brushes from igniting any potential fumes and keeps the brush box sealed. With most diesel engines ignition protection is not technically required, but it’s still a good idea to use this gasket upon reassembly.

The External Regulation Conversion Kit

IMPORTANT: As of June 12, 2017 Compass Marine Inc. was notified that Leece-Neville has discontinued this external regulation kit. We spent an entire year  tracking down every last bit of inventory, of these kits, and actually re-imported over 150 of them from Europe. We then talked Leece-Neville into doing one last production run for us before the machine was scrapped. This allowed Compass Marine Inc. to continue supplying these kits to our readers. The supply is dwindling.

Leece-Neville used to manufacture an external regulation conversion kit for the 8MR series of alternator. The original was a design done for Balmar and then, when Balmar discontinued the Model 81, they added the conversion kit to their product line. We’ve taken the hassle out of finding these kits (now obsolete) and made them available right here: Leece-Neville 8MR External Regulation Conversion Kit.

What’s In The Box

The external regulation conversion kit comes with everything you’ll need, including the wires, bolts and insulators, to make this a simple process.

Step 1

The first step in assembling the kit is to slide the ring end of the wires over the carriage bolts as shown here.

Step 2

Now slide the black plastic insulators over the carriage bolts with the flat side facing the ring and the side with the smaller square facing up as shown.

Step 4

Because voltage & current is running through these wires it’s rather critical they be installed and insulated correctly.  If the insulators are not installed correctly, you can literally create a dead short and ground out on the alternator case. This could ruin your day.

In this image the small square is properly oriented to prevent the machine screw from making contact with the cover plate.

Back Side View

Here’s what it looks like from the back.

Step 4 – Install External Insulators

With the studs, and the internal insulators pressed in place install the large insulating washers over the studs. Next drop the two small washers supplied on top of the insulators, add the nuts and tighten them down.

Inside View

Here’s the view from inside the cover plate with the insulators & studs installed & snugged tight.

Step 5 – Install The Spark Arrestor Gasket

Place the spark arrestor gasket over the conversion plate before connecting the wires to the brush holder.

Step 6 – Slide The Connectors Onto The Brushes

Slide the contacts onto the brushes male studs, in the reverse order you removed the stock regulator wires. It does not matter which way you connect these green wires because one will become the field contact and the other will be connected to the alternators ground stud.

Step 7 – The External Wiring

One last detail you will need to do is to create a jumper wire from one terminal of the plate to the B- / Negative stud on the alternator. This is the black wire in the photo with the yellow crimped ring terminals.

Leece-Neville recommends a 12GA to 14GA wire for this jumper. We’d recommend using a 105C tinned marine wire. 14GA is more than adequate for this jumper.

IMPORTANT: If you do not connect one of the cover plate studs to the alternators negative / B- terminal the alternator will not work. The alternators B- / Negative terminal must also be grounded to the ships DC negative bus. Because many of the 8MR alternators are isolated ground the B- stud is 100% isolated from the case. This is why you can’t just connect the negative brush to the alternator case. It must be connected to the B- stud as shown here.

For future reference, we advise permanently labeling the + field stud so it’s easy to wire and remember which is which. The alternators B+/Output stud gets wired directly to the positive side of your boats electrical system. For best performance we recommend wiring this directly to a battery bank,  preferably the house bank. One reason for this is so you don’t risk blowing the alternator diodes by turning off the battery switch when the motor is running and teh alternator is producing current.

If you wire the alternator directly to a battery, there needs to be a fuse within 7″ of the batteries + terminal post. This fuse should be rated at 150% +/- of the alternators amperage rating.

For a diesel engine tachometer, if the tachometer is alternator sensed,  simply wire to either of the studs marked “AC Tap”. An AC Tap is also called a “Stator Tap”, Stator terminal or “stator pulse”.  On this particular 8MR these stator taps are redundant, so either one is fine. Just don’t use both simultaneously, pick one or the other. You may need to re-calibrate your tachometer after the installation of a new alternator. The8MR series of alternators are a 12 pole alternator.

The Conversion to External Regulation is Complete

This 90A Leece-Neville alternator is ready to be installed and wired to an external multi-stage regulator such as a Balmar MC-614H or Balmar ARS-5H.

IMPORTANT: If installing this alternator to charge a large flooded, AGM or GEL bank you will definitely need a Balmar MC-TSA-80 alternator temp sensor. You will also want to use Balmar’s Belt Load Manager feature and set it to at least level 3 or 4. You can read about programming a Balmar regulator at the link below.

Programming a Balmar Alternator Regulator

Belt Load Manger is a permanent reduction in the maximum field voltage to essentially current limit the alternator to a lower output. This helps the alternator survive driving large loads where maximum output could be required for 30 minutes or more. These are great little alternators but they are definitely not a true high-performance alternator. They need and require adequate protection from overheating events in order to survive charging large battery banks.

DISCLAIMER: While these are good alternators, provided you get a genuine Leece-Neville and not a clone, they are still not a true high output continuous duty alternator. They are really a medium duty alternator. They can be quite reliable but, when pushed hard, they will not last nearly long a as a purpose built high performance alternator.

Here at Compass Marine Inc. we custom build these alternators for less than half the price of a purpose built high output marine duty alternator. The CMI-105-ER is a completed unit that can save you both time and money. If you protect it from over-temp situations you will get long life.

Once converted in this fashion this alternator will be a “P Type” or positive field alternator and can be used with external regulators such as Ample Power, Balmar, Xantrex & Sterling. My personal preference for external regulation is Balmar.

Check out our alternator offerings if you need componets for your self built 8MR such as pulleys, fit kits, spacers etc.

MarineHowTo.com Web Store – Alternators & Regulators

Does This Look Familiar?

This is a genuine Balmar Model 81, not the alternator you saw above just painted white. We have had both a Model 81 and a Leece-Neville 8MR apart on the bench and they share many similarities both on the inside and out. When we build our CMI-105-ER it is built to the same standard as the alternator below.

Balmar no longer sells the model 81, it has been replaced by the newer and very excellent Balmar 6-Series alternators. The 6-Series is a very, very good alternator, with better performance, and a more robust build than the the Model 81. For many years Leece-Neville has been one of the OE suppliers to Balmar, and they still are, for some alternators. Today, most Balmar alternators are physically built in-house by Balmar.

If your goal is pushing an alternator hard, with a large battery bank or you have AGM, GEL or LiFePO4 batteries you would be wise to consider a better & more robust alternator than an 8MR frame unit.

The newer Balmar 6-Series or the new XT-Series small frame alternators are a big leap forward in terms of better cooling, and higher output for longer periods. If you don’t need that type of performance the 8MR is a very good low cost option to pair with a Balmar regulator.

When setting up a Balmar regulator, for the 8MR series, we recommend Balmar’s Belt Load Manager be set to at least level 3 or 4. This will de-rate the available current output of this alternator and allow it to run into large loads for longer periods of time with less risk of over heating.

Running these alternators wide open/full field into large loads, for long duration’s, will eventually cook them. Use alt temp sensing as added insurance and Balmar’s Belt Load Manager as your primary tool to keep these running cool.

Good luck & happy boating!

Regulator Sensing Voltage at Alternator End

The topic of wiring a high performance alternator regulator, and doing it correctly, comes up a lot. One of the most confusing and often misunderstood areas, that can bite into your charge performance, is incorrect voltage sense wiring. This short article deals only with correcting voltage sense wiring mistakes for the Balmar MC or ARS regulators as well as the discontinued Xantrex XAR (made by Balmar).

With a high performance voltage regulator, such as the older Balmar MC-612 or current MC-614, and some others, they include a dedicated voltage sensing circuit. This is a great feature, if you wire it correctly..

NOTE: The Balmar ARS-5 and Xantrex XAR regulators do not have a dedicated positive volt sensing lead. On these models voltage sensing is done between regulator B+ (red) and regulator B- (black). If these wire runs are extended to the battery bank care must be taken to account for the voltage drop in the red wire which can carry as much as 6A +/- to drive the field current. For the best performance you’ll want voltage drop in the regulator B+ wire to be as close to zero as possible. If you’ve not already purchased a regulator, then consider the Balmar MC-614 for it’s added positive voltage sensing wire..

A voltage sensing circuit is a circuit intended to carry minimal to no current so there is minimal voltage drop in this measurement circuit. The voltage sensing circuit should really be considered a voltage correction circuit or a voltage drop compensation circuit.

The voltage sensing circuit works by utilizing these smaller sensing wires in order to compensate for the voltage drop in the larger alternator output wires. The larger alternator positive & negative are actually carrying the high current and even if large will suffer from some voltage drop. Voltage sensing is supplied on these high performance alternator regulators so we can achieve the correct regulator set point voltage, at the battery itself, not just at the back of the alternator. These sensing wires measure the actual battery terminal voltage and allow the regulator to drive the voltage at the battery end to the correct point.

Voltage is the pressure that allows current to flow into the batteries. Incorrect voltage sensing causes your regulator to prematurely begin limiting voltage. Once voltage is held steady current has to decline in order to not over shoot the voltage limit of the regulator. The issues of voltage drop and incorrect voltage sensing leads to longer charge times. Sail boats, more so than power boats, simply want to pack as much energy back into the bank and do so in the shortest time possible. If you have incorrect sensing this can rather dramatically cut into how much capacity you can return in a given period of time.

The voltage drop numbers seen in these three illustrations are the actual voltage drops measured on a boat I worked on two years ago. The alternator output wires, both positive and negative, according to the owner, were sized for a 3% +/- voltage drop. However terminations, fuses etc. were not accounted for in the voltage drop calculation and the length wound up a bit longer than anticipated in the owners original calculations.

In this illustration we have the alternator regulator prematurely limiting voltage to 14.4V because it is sensing the voltage BEFORE THE VOLTAGE DROP OCCURS.. The alternator volt sense circuit is seeing 14.4V, at the alternator, and the regulator is now limiting or holding the voltage steady at 14.4V. Now take a look at what is going on at the battery end. At the battery end the voltage is just 13.79V and considerably less current can flow into the bank at 13.79V than it can at 14.4V.

If you are buying a high performance alternator and regulator some of your performance improvements come from the alternator no longer being what is referred to as “self sensed”. Part of the performance improvements, when moving to external regulation, come from the ability to directly sense the battery terminals, instead of the back of the alternator.

“But RC it’s only a 3% voltage drop?”

While 3% sounds good, 3% on a voltage limit of 14.4V = 0.43V drop. This wire drop is on top of any terminations or fuses these wires pass through on the way to the bank. The net result is an alternator regulator limiting voltage to 14.4V and the batteries seeing just 13.97V. That .4V makes a big difference in how much current your batteries can take at XX SOC…

“But RC as current declines, when the battery approaches full, there will be little to no voltage drop. The batteries will eventually get to target voltage, so what’s the big deal?”

Yes, this thinking is in-fact correct. However there are a few issues with it.

#1 Yes, voltage drop is directly related to the current flowing through the wires. In an ideal world we’d have all the time we’d want, or need, to charge the batteries. With cruising boats we simply don’t have this time or the luxury of 10+ hours to do this. For the reasons of time alone voltage drops, in system wiring, cut into the charge speed of the high performance system you just paid buku bucks for.

#2 Once the regulator attains 14.4V+ the time clock or cycle algorithms begin running on the absorption cycle. Batteries need a good absorption charge cycle for optimal health. If the regulator is dropping to float just about the time the batteries physically come up to 14.4V+, due to the incorrect voltage sensing issue, we really get a shorter and poorer absorption cycle despite the regulator thinking the bank did. This, compounded on the many other charging problems I see, can lead to chronic undercharging. An inadequate absorption cycle can result in the effects of sulfation setting in sooner than it should.. With voltage drop the regulator has been in what it thinks is absorption for longer than the batteries have. Think about this. Incorrect placement of the voltage sensing wires is easy to address and fix with external regulation.

If you think voltage sensing impacts lead acid batteries in a bad way, the impact on LiFePo4 batteries, a very fast growing technology, can result in almost no charging performance at all, when you have too much excess voltage drop.

Don’t let your regulator enter absorption before your batteries get there!!

Regulator Volt Sense to Battery – Positive Side Only

In this illustration I have run the regulators dedicated positive voltage sense wire direct to the house bank. As we can see the regulator is now compensating by 0.29V. This is the voltage drop in the alternator outputs positive wire. The regulator is now producing 14.69 volts, across B+ & B- in order to get what it thinks is 14.4V across the voltage sensing circuit.

Because we have not completed the voltage sensing circuit, and the negative wire is still connected to the back of the alternator, we have not compensated for all the voltage drop, only half of it.

I know, I know “Balmar says to connect regulator negative to the alternator.”

What they actually say is this:

“In most applications, this wire can be connected directly to the alternator’s ground terminal post.”

For a cruising sailboat they are giving you very general information in this regard. The key word in that sentence is “most”. Heck most boats in this country are power boats who run engines long enough for incorrect voltage sensing to not matter as much. If you own a trawler or power boat you probably fall into this “most applications” scenario. However if you want to run your engine for a maximum of 1 hour per day, and get the absolute most from your charging system in that time, then you really don’t qualify for the “most applications” discount….

If you pick up the phone, call Balmar, and talk to Dale etc. they will confirm exactly what I have just shown you here. It simply needs further clarification in the manual for those who want the utmost in performance..

Positive & Negative Regulator Volt-Sense to Battery End = Correct

Finally we now have correct voltage sense wiring. As can be seen the regulator is now driving the alternator to 15.01V in order to have 14.4V at the battery end. The voltage sensing circuit on Balmar and the Xantrex XAR regulators is a CIRCUIT. This means the red wire and the regulator negative wire both need to see battery terminal voltage for optimal performance.

NOTE: In the spirit of simplicity of the illustration these drawings lack an alternator output fuse. This fuse would be within 7″ of the battery banks positive terminal. They also lack a positive volt sense wire fuse, also within 7″ of the battery banks positive terminal…

Get all the speed & charge performance you’ve paid for by wiring your alternator positive & negative output direct to the house bank. After you’ve done that wire the volt sensing circuit direct to the positive and negative bank terminals as well. Like anything it’s all in the little details..

Balmar MC-614 Voltage Sensing Terminals

These are the actual terminals used by the Balmar MC-614 regulator to make the voltage sensing circuit work. It requires both the regulator B- terminal and the + volt sense terminal to get accurate voltage sensing.

“But RC, the black wire in the regulator harness is powering the regulator and field current so it will have voltage drop.”

While I like the way this reader was thinking, I can explain why this thinking misguided. The regulator black wire in the “Ford Plug” is not carrying the negative field current. The field current, on the negative side, is carried by the alternators B-/Neg. The red wire in the Ford harness supplies positive field current and it returns via the alternator B- not the regulator B-. On average, with a typical marine alternator at full field, we measure 0.1A to 0.3A on regulator B-/Black. On the standard Balmar harness this amounts to roughly a 0.03% voltage drop.

If you extend the harness you can always bump the wire gauge but with so little current carried on regulator B- it is easy to see why voltage sensing is so vastly improved by moving regulator B- to the bank being charged.

No Voltage Sensing at Battery – 1 Hour Charge

In order to try and show what the impact can be on a high performance charging system I set up to recreate a scenario I had on a customer’s boat.

This was a race boat and light and fast was the game. As such the bank was designed to be cycled to approx 35% SOC as opposed to 50% most cruisers would do. The cost of the batteries was not the issue for this owner. Battery weight and getting as much energy back into them, in the shortest time was the main goal. He chose TPPL AGM’s (thin plate pure lead) for their ability to take a high charge current rates yet he was not happy with how long his batteries were staying in bulk.

With a .5C charge capability on-board (.5C = 50% of bank Ah capacity) and Odyssey TPPL AGM batteries he should have been doing better than he was. I ran his alternator in bulk charge and measured a .73V drop from the alternator end to the battery end. Not a good find on a boat demanding the utmost in fast charging…. I fixed this issue by addressing the placement of the voltage sensing wires and beefing up both the positive and negative alternator output wires.. Performance increased, and all was good.

For this article I took a brand new Odyssey PC2150 battery (Group 31 12V AGM), that I had just tested at 100.2Ah’s of capacity at the 20 hour rate.. I then discharged the bank down to 11.85V at 77F and the 20 hour rate of 5A. This left the battery at 35% SOC or about 65% discharged. The battery was then recharged with an approx .7V drop at 50A. I set the charger for a 14.7V absorption voltage. The results are in the graph above. Click on the graph to make it larger.

Points to Ponder:

*In 1 hour of charging, at a .5C charge rate, the battery never exceeded 14.3V.

*At just 14.0V, measured at the battery terminals, the charger began limiting voltage. When measured at the charger end, it was seeing 14.7V and it began holding the voltage steady.

*Once the voltage is held steady current tapers off and charging speed reductions are happening.

*Maximum bulk time was limited to 30 minutes at 50A, due to the voltage drop. This resulted in just 41.93 Ah’s delivered to the battery in the 1 hour recharge period.

Voltage Sensing at Battery Terminals – 1 Hour Charge

Do you think it looks a little different with good voltage sensing..?

*In 1 hour the charge source delivered 49.37 Ah’s to the battery. This is an improvement of 7.44 Ah’s in just a short 1 hour charge cycle. This equates to a percentage increase in charge performance of approx 17.7%, just by moving two small wires.

*Bulk charge, at 50A, increased by 20 minutes to a full 50 minutes of bulk charging. Remember this was a 100Ah battery charged at 50A for just 1 hour.

*The battery actually attained the absorption voltage set point of 14.7V. This is healthier for the battery than stopping at 14.3V. It can help limit some of the effects of sulfation, even in a short 1 hour recharge.

*In the previous test, with no voltage sensing, that battery would suffer performance issues considerably faster due to never even attaining the 14.7V target with daily 1 hour recharges.

Note: Every system and battery bank will perform differently and these graphs may not be representative of the system on your boat. As batteries age the charge acceptance ability diminishes and they will attain absorption voltage faster & easier and will thus begin limiting current sooner in the SOC range.. Getting a good long absorption cycle, with the correct terminal voltage, is but one piece of the battery charging puzzle and good voltage sensing circuit can help with this.

Voltage Sense Wiring Blunders

We’ve discussed the importance of good voltage sensing, in relation to charging performance, but it is not always as easy as it appears.. Let me try and sum it up in one line..

YOU CAN ONLY SENSE VOLTAGE AT THE BATTERY TERMINALS IF THE ALTERNATOR IS ALSO CONNECTED TO IT!!!

I know some will still not understand what that means so we are going to delve deeper. Unfortunately I see and correct this blunder far more than I ever should and this one is a battery destroying blunder.

On the typical factory wired boat the alternator output, also called B+, is wired over to the big post on your starter motor. From there it picks up the large wire that comes from the “C” post or “common” post of your 1/2/BOTH battery switch. This is how the alternator gets current to your batteries, by sharing the same wire the starter motor uses.

This method of wiring a factory alternator is cheap, easy and saves the builders lots of money. Some builders do a better job and do direct wire the alternator to the house bank but these are usually high quality builders, not your average production builders.

In this overly simplified illustration we simply have the alternator wired direct to the “C” post of the battery switch. It is easy to see how the battery switch becomes a charge directing switch in this scenario.

Set it to #1 and the alternator charges bank #1

Set it to #2 and the alternator charges #2

Set it to BOTH and the alternator charges BOTH

Now what happens if we add a high output alternator, and leave it wired this way? What happens if we leave it wired this way and then run volt sensing to the house bank??

Volt Sense Wiring Blunder – Charging House

Okay in this illustration everything appears to be working fine, and so long as we never move the switch to #2, it will be..

The Lifeline AGM battery is at its target voltage of 14.4V and is getting charged via the 1/2/BOTH switch directing charge current to the HOUSE bank denoted by the orange switch line to position #1.

In this scenario the HOUSE comes up to proper voltage and everything works. HOUSE at 14.4V START at resting open circuit voltage of 12.6V or so.

NOTE: This diagram assumes no Echo Charger, Duo Charger or Combiner to charge bank #2..

Volt Sense  = FAIL !!!!!

“Mission control, we have a problem”… Follow the orange line and try to figure out where we’ve made a mistake?

#1 The regulator is sensing voltage at the HOUSE bank and waiting to see a change.

#2 The alternator is feeding directly to the START battery but the voltage being sensed by the regulator is not budging, on the house bank, and why would it?

#3 In this scenario the regulator remains in FULL FIELD (full output mode) driving the voltage of bank 2 through the roof! We have an alternator being told to stay in bulk charging and a START battery that was nearly full to begin with. The result is the bank 2 voltage rising uncontrolled and frying the battery.

I have seen far too many batteries destroyed by this particular blunder over the years and the manuals apparently do not make this clear enough, for all installers.

Volt Sense = Correct

If you must leave your new high performance alternator wired through the 1/2/BOTH switch then this is the correct wiring for the voltage sensing.

#1 Negative regulator or regulator B- goes to HOUSE bank negative terminal.

#2 Positive volt sense goes as close to the bank as it can be without the ability to decouple voltage sensing from the bank receiving charge current. This means the “C” post of the battery switch is the absolute closest you can get to the battery terminals and be safe.

Is this ideal? No, but if you choose to leave the alternator output/B+ wire passing through the starter cable, via the “C” post of the battery switch, this is the best you can do without toasting the start battery, at some point in time.

Service Disconnect Switch

When you do wire your alternator direct to the house bank please consider installing an alternator service disconnect switch. A service disconnect switch is a switch placed visibly in the engine space, and clearly labeled, so a service technician can isolate the alternator from the battery bank, while working on the engine, without having to remove a fuse to do so.

This is a Blue Sea Systems m-Series #6006 battery switch in the positive alternator feed. This switch is rated for 300A continuous. During normal use this switch always remains in the ON position. The only time it is turned off would be when a service technician is working on the engine. I prefer to mount this in the engine space so it is out of sight and out of mind of guests on-board who are; “just to trying to help.”.

IMPORTANT: If wiring a service disconnect switch it is critically important to place the Balmar MC-614 B+/Power/#2 terminal and alternator B+/Output on the alternator side of the service disconnect switch. The reason for this is simple. If you or a tech forgets and leaves the switch in the OFF position, the regulator can’t boot up without the alternator connected to the battery bank. Allowing the regulator to boot into a zero load alternator can destroy the alternator. A regulator that has a separate positive volt-sense wire and a regulator B+ is yet another reason why the MC-614 is a better choice than the ARS-5 regulator.

Please remember that any wires leading to the house bank, or another +12V source, will get fused at the banks positive terminal or within 7″ of it. This includes the alternator B+, regulator positive, volt sense positive and the brown ignition wire. The alternator B+ feed should be fused at a minimum of 150% of the alternators output rating.

Wire safe, wire it correctly and your system will perform as it should and in the manner you paid for..