Battery and charging systems

[dhays]

With the start of school (my wife is a teacher) we have used the boat less recently and I have been digging around in the various systems trying to figure things out. I am discovering and learning things all the time. Yesterday, I was looking at the batteries and charging system.

My boat still has the original 3 200AH sealed lead acid batteries that came with the boat back in 2010. The PO had replaced the engine start battery, and both thruster/davit batteries with Lifeline AGMs. All of those are 8D sized batteries I believe. Shortly after I bought the boat the genset start battery died, it was an original sealed lead acid as well and I replaced it with an AGM.

I was looking at the electrical system and found that originally, it looks like the boat had three Balmar Duo-Charge chargers. One each for the thruster batteries, genset start battery, and engine start battery. The chargers for the thruster and genset battery are working but the charger for the engine start battery wasn't. After some time, I discovered that the Duo-charger for the start battery was disconnected. Instead I found a BlueSeas ACR connecting the positive bus to the start battery.

So as near as I can tell, when the engine is running the alternator is providing charging energy to the positive bus, the 2 duo-chargers are connected there and then provide up to 30 amps of charging to the thruster batteries and the genset battery when it senses charge voltage above 13v. The ACR connects the positive bus to the engine start battery.

It appears that the Inverter/Charger also is connected the same way but with a solenoid that will connect it to the positive bus. I haven't yet figured out how the Genset is connected to provide charge but I would assume that it also is connected to the positive bus.

So I have a few questions. Does the above sound correct or am I missing something basic?

The Balmar Duo-chargers are set to the default charge profile which is for Lead Acid batteries (according to the little green LED light). They can be set for a charging profile for AGM (using some kind of magnetic probe I think). I don't think this was changed when the PO replaced the origina LA batteries. I am guessing that I should change those two Duo-chargers to an AGM profile for my thruster and genset batteries?

Any idea why the Duo-charger was disconnected for the engine start battery and the ACR used instead? The Duo-Charger will quit if the charge demand exceeds 30amps. Is is possible that if the start battery was severely depleted that the charge demand could have gone over the 30 amps and therefore never "turned on" to supply charge to the battery? Using the ACR, charging current will always be supplied to the start battery regardless of how high the demand would be.

Since the start battery and the house batteries are of different types (lead acid vs AGM) is there a problem using the ACR to connect those two types together for charging purposes? I am not sure what the charging profile is for the Inverter/Charger, but if the Duo-chargers are any indication my guess is that it is set for lead acid. Not sure if this will hinder the charging of my AGM start battery as I believe it could accept a faster charge than what the LA house batteries can.

Finally, if any of you have read this far, above the Genset solenoid, there is an On/Off switch. I can't figure out what this switch actually does and it has been in the off or open position since I have owned the boat. You can see the switch above the solenoid towards the right of the picture. The output from the Duo-charger goes to this switch as well. I don't know the function of this switch unless it is there to close the circuit if the solenoid doesn't have enough power to do it?

 

[O C Diver]

Complicated!

As far as the switch above the solenoid. That solenoid looks like it would parallel two batteries, maybe to start the generator off of another battery. The switch would likely hold the batteries in parallel, maybe for charging. looks like there is a wire coming from the Duo charge unit to charge one of the batteries. All of this is hard to figure out if you can't see where the wires are going. Can you verify where the wires are going from the solenoid? Usually the start solenoid is mounted on the starter motor or near by.

Ted

 

[dhays]

Thanks Ted. Yeah, hard to trace but I'll work on it. I have started to piece together a diagram bits at a time.

As near as I can tell, there are solenoids that interrupt the positive cable from the battery for each of the systems. ie, there is a solenoid which closes the circuit between the thruster batteries and the thrusters/crane. Same is true for the House panel, engine start, and genset start, and shore powered charger. Each solenoid is controlled by a switch on the 12v panel in the PH.

So the solenoid simply connects the circuit between the genset and its start battery. I am thinking that the switch may override that solenoid in the event that the house bank, which supplies the 12v for the solenoids, is complete dead. That way you can connect the Genset to its start battery and and get it started. While that makes sense, I can't figure out how that would actually be wired. I have a question into North Pacific to be sure and should hear back soon.

 

[Bruce B]

Interesting charging system Dave.
Is there no person at North Pacific Yachts that you might be able to speak to about It? I find that if needed a system can be studied to find the answers but someone who has knowledge might be able to fill in the gaps pretty quickly...
Might save you some work.
Bruce

 

[dhays]

Interesting charging system Dave.
Is there no person at North Pacific Yachts that you might be able to speak to about It? I find that if needed a system can be studied to find the answers but someone who has knowledge might be able to fill in the gaps pretty quickly...
Might save you some work.
Bruce

There is, and I just asked on the NP website. I can always email or call Trevor Brice directly and he will get back to me right away. While I have done that a number of times, I don't like to be too much of a pest.
There are other NP owners who are more knowledgeable than I as well, Dan on "Rebel" being one them.

I was curious as to why the PO might have stopped using the Balmar Duo-Charge and gone with the ACR? The Duo-charge seems like a great way to charge the non-house batteries and was how it was setup from the factory. The PO's memory is even worse than mine so asking him wouldn't help and he wouldn't have done the work himself in any case. So if anyone has experience with the Duo-charge and could hazard a guess... Where is Mainsail when I need him.

 

[O C Diver]

Thanks Ted. Yeah, hard to trace but I'll work on it. I have started to piece together a diagram bits at a time.

As near as I can tell, there are solenoids that interrupt the positive cable from the battery for each of the systems. ie, there is a solenoid which closes the circuit between the thruster batteries and the thrusters/crane. Same is true for the House panel, engine start, and genset start, and shore powered charger. Each solenoid is controlled by a switch on the 12v panel in the PH.

So the solenoid simply connects the circuit between the genset and its start battery. I am thinking that the switch may override that solenoid in the event that the house bank, which supplies the 12v for the solenoids, is complete dead. That way you can connect the Genset to its start battery and and get it started. While that makes sense, I can't figure out how that would actually be wired. I have a question into North Pacific to be sure and should hear back soon.

What size generator do you have?

If the solenoid is as you describe, it needs to be engaged whenever the generator is running? Seems like an added layer of complexity (AKA additional failure point). Or are you saying that the solenoid is normally closed and flipping the switch interrupts the circuit?

Ted

 

[dhays]

What size generator do you have?

If the solenoid is as you describe, it needs to be engaged whenever the generator is running? Seems like an added layer of complexity (AKA additional failure point). Or are you saying that the solenoid is normally closed and flipping the switch interrupts the circuit?

Ted

6kw Northern Lights. I know very little but... in order to start the genset, there is a switch on the 12v panel that (I believe) closes the connection in the solenoid. If I forget to turn that on (which I have done) then the genset won't start as it has no battery power from the start battery. Flip the switch, solenoid closes, then the genset can be started.

 

[Rebel112r]

The switch on the 12 volt panel does exactly what you said. With it off, no voltage at the gen set. I figured it was done for safety reasons, same is true for the thrusters and main engine start batteries and the davit. No heavy cables carrying voltage when not in use. I have ACR's controlling charging, one for house and inverter charger, and another controlling charge from engine alternator. So all batts get charged, either off alt or off of invertor. Generator is stand alone, using its own batt and charging only itself. There is a way to connect house batts to gen to get it started, if genset batt fails. Dan

 

[O C Diver]

6kw Northern Lights. I know very little but... in order to start the genset, there is a switch on the 12v panel that (I believe) closes the connection in the solenoid. If I forget to turn that on (which I have done) then the genset won't start as it has no battery power from the start battery. Flip the switch, solenoid closes, then the genset can be started.

Hmmm. Think I would add at least 1 of those solenoids to my spares.

Ted

 

[dhays]

The switch on the 12 volt panel does exactly what you said. With it off, no voltage at the gen set. I figured it was done for safety reasons, same is true for the thrusters and main engine start batteries and the davit. No heavy cables carrying voltage when not in use. I have ACR's controlling charging, one for house and inverter charger, and another controlling charge from engine alternator. So all batts get charged, either off alt or off of invertor. Generator is stand alone, using its own batt and charging only itself. There is a way to connect house batts to gen to get it started, if genset batt fails. Dan

Thanks Dan, I appreciate the clarification. Sounds like ours were setup differently. I actually like the Duo-charger but am unsure why it was disconnected in favor of the ACR for the engine start battery. The only thing I can think of is if possibly they had the situation where the AGM start battery was asking for more than 30amps of charge. In that situation the Duo-charge will simply shut off and try again later. In that situation, a really dead battery might never get a charge.

There is another way of wiring them so that they will go ahead and provide the 30 amps of charge even if the battery wants more. I should look into it some more and give Trevor a ring.

 

[Rebel112r]

OC I have had a bow thruster solenoid go out, temp fix was to move the cables to one side. Thruster then had juice all the time. OK, till another problem arises.

 

[dhays]

Hmmm. Think I would add at least 1 of those solenoids to my spares.

Ted

That is an excellent suggestion. All of the solenoids are the same and it would really suck if one of them failed. A spare would cover me for all of them. Thanks!

 

[CMS]

Dave,

Hard to tell what is going on there without a diagram. The relays look like the Tyco EV 200's or they are also sold under the Blue Sea label. These are 500A relays so should be plenty robust even for most thrusters.

The Duo Charger is designed to be able to drive a manually operated contactor if the loads are regularly going to exceed the 30A rating of the Duo. I can't tell where your ground wires go but they may be driving one or more of those relays via a switch somewhere.

The reason the duo may no longer be operable on the main engine is the draw of some of these big engines often exceeds 30A. At idle, in cold water which takes the engine a long while to warm up, the battery bank can still be discharging even with the engine running.

I have had more than one large diesel with a pre-heater that could pull upwards of 200A with a cold engine. At idle, with cold Maine water, it could suck the owners start battery dead while the engine was running due to the high cut-in speed of the stock alt. In a situation like this an ML-ACR is a much better choice than a Duo Charger. We were able t use the 2nd engine mounted alt, a high performance alt, to charge at low idle and keep the bank slightly over 13V until the pre-heater shut down..

You really need to figure out what your engine loads are. In other words, what does the engine consume in DC current just to run? This is where you may find the answer as to why the Duo was replaced by an ACR...

I also notice that none of the Duo's are utilizing their temp sense circuits...

As for that battery switch? Looks to be a manual override of the EV 200 contactor below it. Again, we really need a diagram to know more.

 

[CMS]

Since the start battery and the house batteries are of different types (lead acid vs AGM)

They are both "lead acid" batteries though they may require differing charge voltages.

is there a problem using the ACR to connect those two types together for charging purposes? I am not sure what the charging profile is for the Inverter/Charger, but if the Duo-chargers are any indication my guess is that it is set for lead acid. Not sure if this will hinder the charging of my AGM start battery as I believe it could accept a faster charge than what the LA house batteries can.

I know I have likely beat this horse to death but the battery type (in words on a charger eg; AGM, GEL, Flooded) is quite often pretty irrelevant. What is relevant is the batteries recommended absorption and float voltage.

As a group boaters really need to stop looking at the words on a chargers pre-set list and instead look at the VOLTAGES behind the words. AGM, GEL, Flooded, FDC etc. are words and they mean absolutely nothing without knowing the VOLTAGES behind those words.

One manufactures voltage for AGM will NOT always be the same as the next thus you should only focus on the VOLTAGES the words represent. Sometimes you can also see different absorption times behind the words and this too is very useful information. For some AGM batteries you will be much better served using the FDC setting than an AGM setting but a custom setting will always better be able to match the manufacturers recommended absorption & float voltages.

For example Trojan's are best charged at 14.8V absorption & 13.5V float for a PSOC type use. If an installed starting battery can also be charged at 14.8V & 13.5V then the charger can charge both even if one is flooded and the other AGM.

An ACR just applies the same charge voltages to each bank because they are charging in parallel.. This is really no different than most all so called "smart-chargers" which feature multiple outputs. If the float voltage requirements are also the same, or very similar, then one charger can feed two different battery types without issue. All batteries should be charged temp compensated..

VOLTAGE (and time or timer algorithm) is the key not the words.


While a smart charger may have outputs for "three-banks" it is still one charger with one single voltage setting used at a time. You can't for example put a GEL battery that needs 14.1V on output #2 and a Trojan that needs 14.8V on output #1 and then set the charger to FLOODED because you will cook the GEL battery. If you set it to GEL then you chronically under charge the Trojan and also ruin it.

Here is a prime example of ignore the words and focus on the recommended VOLTAGES

Here are some manufacturer suggested charging voltages:

AGM's - Which AGM Preset works?:

Lifeline AGM's = 14.4V & 13.4V = AGM Preset #1
Odyssey TPPL AGM's = 14.7V & 13.6V = Neither AGM Preset
Firefly AGM =14.4V & 13.2V = Neither AGM Preset
Mastervolt AGM = 14.4V & 13.2V = Neither AGM Preset
Full River AGM = 14.7V & 13.7V = Neither AGM Preset
Rolls AGM = 14.7V & 13.7V = Neither AGM Preset
East Penn/Deka = 14.6V & 13.6V = Neither AGM Preset
US Battery AGM = 14.4V & 13.4V = AGM Preset #1
Trojan AGM = 14.4V & 13.5V = Neither AGM Preset

This is why boaters should always focus on buying chargers that have a custom setting. Please do not focus not on the words but instead focus on the voltages that the words are representing..

How about Trojan Flooded batteries? Which Flooded preset works for Trojan flooded batteries??

Trojan Flooded = 14.8V & 13.5V = Neither are ideal. So you use custom and set it at 14.8V and 13.5V

How about Deka / East Penn Flooded

Deka Floded = 14.7V & 13.8V = Neither are ideal. So you use custom and set it at 14.7V and 13.8V

* This is but one example of one charger. Some so called smart chargers are so dumb as to only have three options AGM, GEL or FDC.

You will generally be best served to use the same brand and type of battery with a multi-output charger or ACR/VSR/Combiner etc. and set the charge voltages for those batteries correctly but they can certainly be mixed if the voltages align. If you have a mixed use scenario, always set the voltages for the most expensive bank....

 

[Ski in NC]

Best thing is to draw an actual schematic of the whole DC system showing major bits like batts, alts, ACR's, switches, panel feeds, starters, inverters, chargers. With that on one sheet of paper, the system can be reviewed.

Some of these boats start out with complicated systems, then folks add more stuff and you end up with a birds nest of cable. Then half the stuff is redundant and nobody really understands the thing as a whole. Run into this all the time.

 

[dhays]

Hard to tell what is going on there without a diagram. The relays look like the Tyco EV 200's or they are also sold under the Blue Sea label. These are 500A relays so should be plenty robust even for most thrusters.

Yeah, I am working on the diagram. I may be able to get a starting point from the manufacturer and then go from there.

The Duo Charger is designed to be able to drive a manually operated contactor if the loads are regularly going to exceed the 30A rating of the Duo. I can't tell where your ground wires go but they may be driving one or more of those relays via a switch somewhere.

The reason the duo may no longer be operable on the main engine is the draw of some of these big engines often exceeds 30A. At idle, in cold water which takes the engine a long while to warm up, the battery bank can still be discharging even with the engine running.

Currently the Duo Chargers are all wired in the conventional way and not with a manual override. I never thought about the possibility of increased electrical draw on a cold engine at idle. My primary thought was the amount of draw that a low SOC start battery would demand for charging. Still way too much that I don't know about these larger and more complicated systems. I will see if I can find out some information on possible current draws from my Cummins QSB 5.9.

The engine draw makes sense in that I was confused as to why a start battery would require more amperage to charge than a bank of 2 thruster batteries. I tried to find out what charge demand a Lifeline 8D start battery may have but didn't have any luck.

You really need to figure out what your engine loads are. In other words, what does the engine consume in DC current just to run? This is where you may find the answer as to why the Duo was replaced by an ACR...

I will see what I can find out.

I also notice that none of the Duo's are utilizing their temp sense circuits...

Yup, I noticed the same thing that that is something that I'll want to add. The Genset and Engine start batteries are both in the ER so they are the ones that I think would be the most critical.

As for that battery switch? Looks to be a manual override of the EV 200 contactor below it. Again, we really need a diagram to know more.

That is my guess as well and will see about tracing wires.

I know I have likely beat this horse to death but the battery type (in words on a charger eg; AGM, GEL, Flooded) is quite often pretty irrelevant. What is relevant is the batteries recommended absorption and float voltage.

As a group boaters really need to stop looking at the words on a chargers pre-set list and instead look at the VOLTAGES behind the words. AGM, GEL, Flooded, FDC etc. are words and they mean absolutely nothing without knowing the VOLTAGES behind those words.

Excellent point and one that I obviously needed to be reminded of. While the Duo Charger offers 4 profiles for different battery types, it is also possible to program the lower and upper voltage limits for those. I will see if I can figure out what the Duo Chargers preset settings really mean and see if they match up with the recommended voltages for the Lifeline AGM. If not, I can try and program them into the Duo Charger.

An ACR just applies the same charge voltages to each bank because they are charging in parallel.. This is really no different than most all so called "smart-chargers" which feature multiple outputs. If the float voltage requirements are also the same, or very similar, then one charger can feed two different battery types without issue. All batteries should be charged temp compensated..

This is why I am wondering about the ACR. It is paralleling a house bank of old flooded LA batteries outside the engine space and a Lifeline AGM located in the ER. Both sets of batteries would be getting the same charge if I understand how my system is setup correctly. This is where going back to using the Duo Charger would give some advantages as I would then have different charging profiles for each and they each could be temperature compensated.

Thanks for the help Rod, I really appreciate it. I will dive back into the boat again this next weekend and see what I can come up with.

 

[Capt.Bill11]

It all sounds stupidly complicated to me.

I'd set it up where the gen charger just charges the gen battery. The thruster charger just charges the thruster battery and the other charger just charges your starting batteries.

You must have house batteries? What charges those? Or are your starting batteries used as house batteries?

Then I'd set it up so the gen alternator just charges the gen battery. And the mains just charge the starting batteries and house batteries through a combiner.

If your starting batteries are your house batteries I'd set up a simple on/off switch that can parallel your gen battery in to you start batteries if you need a quick jump start.

I'd just let a charger take care of the charge on thruster battery.

 

[dhays]

It all sounds stupidly complicated to me.

I'd set it up where the gen charger just charges the gen battery. The thruster charger just charges the thruster battery and the other charger just charges your starting batteries.

You must have house batteries? What charges those? Or are your starting batteries used as house batteries?

While it does sound complicated, and to look at it it can be confusing but the basic design I think is relatively simple. All charging sources go the house bank (separate bank of LA batteries). From there, each other battery has its own Duo Charger that will send up to 30 amps of charge current to it.

I do like this setup in that the charging profile can be configured for each battery individually which is nice when you have a mix of different types of batteries. In my case, I don't know that the PO ever changed the charging profiles when he changed out the batteries. While there doesn't seem to be any temperature compensation, the Duo Chargers mean that each battery can be setup with its own temperature compensation. My genset battery is in the ER but my thruster batteries are in the aft lazarrett. Entirely different temperatures.

The ACR that was added likely is there to solve a problem that the PO found with the Duo Chargers 30amp cutoff, ie if the charge demand is higher than 30 amps it shuts down. There is a feature in the Duo Charger than provides for a manual override for this cut off but the PO decided to go with the ACR instead. That is fine other than it means that my house bank and engine start battery are paralleled for charging purposes even though they are of two different types and in two very dissimilar locations.

 

[dhays]

Some of these boats start out with complicated systems, then folks add more stuff and you end up with a birds nest of cable. Then half the stuff is redundant and nobody really understands the thing as a whole. Run into this all the time.

This is kind of where I'm at. I think that once I put in the time to figure out a schematic then it will start to be more clear. Part of my problem is my native ignorance of all things electric.

 

[CMS]

This is why I am wondering about the ACR. It is paralleling a house bank of old flooded LA batteries outside the engine space and a Lifeline AGM located in the ER. Both sets of batteries would be getting the same charge if I understand how my system is setup correctly. This is where going back to using the Duo Charger would give some advantages as I would then have different charging profiles for each and they each could be temperature compensated.

Thanks for the help Rod, I really appreciate it. I will dive back into the boat again this next weekend and see what I can come up with.

The Duo Charger is a relatively simple "voltage follower", though with slightly more control than an Echo Charger..

This means it follows the voltage of the house banks charge source. You really don't get an independent float or a buck/boost feature to boost voltage to another bank. It is not an independent 3 or 4 stage charger it is simply a voltage following device with a voltage cap setting..

There is a lot of misunderstanding regarding what the Duo will do and what it won't do:

"It will float the start battery when it senses it needs float." = INCORRECT

"It will charge the start battery with its own 3 stage charge profile." = INCORRECT


What you actually can control:

Turn On/Excite Voltage is adjustable. This is the voltage at which it activates and starts passing currenr to the start battery.

Output Voltage Limit/Cap can be reduced below the house bank voltage but it can not and will not go higher than house voltage. This is nothing more than a voltage limit for the start battery or output side of the DDC.

It will not drop to a float voltage unless the house bank has dropped to float.

An ACR works similarly only it is bi-directional, passes lots more current, but it can not have a voltage limit on the output side, meaning don't connect a GEL starting battery to a bank of Trojan's... If both banks charge with similar voltages the DDC really gains you very little.

 

[dhays]

There is a lot of misunderstanding regarding what the Duo will do and what it won't do:

"It will float the start battery when it senses it needs float." = INCORRECT

"It will charge the start battery with its own 3 stage charge profile." = INCORRECT


What you actually can control:

Turn On/Excite Voltage is adjustable. This is the voltage at which it activates and starts passing currenr to the start battery.

Output Voltage Limit/Cap can be reduced below the house bank voltage but it can not and will not go higher than house voltage. This is nothing more than a voltage limit for the start battery or output side of the DDC.

It will not drop to a float voltage unless the house bank has dropped to float.

An ACR works similarly only it is bi-directional, passes lots more current, but it can not have a voltage limit on the output side, meaning don't connect a GEL starting battery to a bank of Trojan's... If both banks charge with similar voltages the DDC really gains you very little.

Best explanation I have seen yet Rod, thanks.

I need to do some digging to find more information about my system's configuration. There are some major pieces that I haven't yet figured out.

 

[Capt.Bill11]

While it does sound complicated, and to look at it it can be confusing but the basic design I think is relatively simple. All charging sources go the house bank (separate bank of LA batteries). From there, each other battery has its own Duo Charger that will send up to 30 amps of charge current to it.

I do like this setup in that the charging profile can be configured for each battery individually which is nice when you have a mix of different types of batteries. In my case, I don't know that the PO ever changed the charging profiles when he changed out the batteries. While there doesn't seem to be any temperature compensation, the Duo Chargers mean that each battery can be setup with its own temperature compensation. My genset battery is in the ER but my thruster batteries are in the aft lazarrett. Entirely different temperatures.

The ACR that was added likely is there to solve a problem that the PO found with the Duo Chargers 30amp cutoff, ie if the charge demand is higher than 30 amps it shuts down. There is a feature in the Duo Charger than provides for a manual override for this cut off but the PO decided to go with the ACR instead. That is fine other than it means that my house bank and engine start battery are paralleled for charging purposes even though they are of two different types and in two very dissimilar locations.

The page below may indicate what the ACR is all about.

"All charging sources go the house bank (separate bank of LA batteries)."

Does that mean all the Chargers and alternators feed to the house bank?

 

[dhays]

The page below may indicate what the ACR is all about.



"All charging sources go the house bank (separate bank of LA batteries)."



Does that mean all the Chargers and alternators feed to the house bank?

As near as I have been able to determine so far, yes the engine alternator and the charger feed the house bank.

 

[JDCAVE]

Hey Rod: great commentary, thanks!

Dave: in my setup, when the the start battery is isolated (99% of the time), it can only start the engine and run the windlass. In your setup, I would imagine the draw from the windlass could/would exceed the 30 amp maximum of the duo charge, thus the use of the ACR. The PO used the Blue Seas ACR to charge the start batteries, which were two deep cycle Trojan T-105s. In my "wisdom" I replaced them with high cranking Group 24's and I didn't realize the function of the ACR, which I had switched to "off", as I had thought the Duo Charge charged the start battery when in fact its role was to charge the thruster batteries. It was just coincidence,that I had an electrician go through my system to explain the setup to me that he discovered that I was not charging my starter batteries at all when the batteries were I combined with the ACR. I now have a Mastervolt voltage regulator to charge the house, starter and generator batteries from the alternator charging source. Actually the generator battery has its own dedicated Prosport charger so there is redundancy. I also have a Prosport charger on the starter batteries. The only occasion I use the Blue Seas ACR is to combine the house and starter systems when dropping and raising the anchor. We then switch it back to the "off" position. Combining the batteries is probably not necessary but the windlass is a large Plath, so it's what we do.


Jim
Sent from my iPad using Trawler Forum

 

[dhays]

Hey Rod: great commentary, thanks!

Dave: in my setup, when the the start battery is isolated (99% of the time), it can only start the engine and run the windlass. In your setup, I would imagine the draw from the windlass could/would exceed the 30 amp maximum of the duo charge, thus the use of the ACR. The PO used the Blue Seas ACR to charge the start batteries, which were two deep cycle Trojan T-105s. In my "wisdom" I replaced them with high cranking Group 24's and I didn't realize the function of the ACR, which I had switched to "off", as I had thought the Duo Charge charged the start battery when in fact its role was to charge the thruster batteries. It was just coincidence,that I had an electrician go through my system to explain the setup to me that he discovered that I was not charging my starter batteries at all when the batteries were I combined with the ACR. I now have a Mastervolt voltage regulator to charge the house, starter and generator batteries from the alternator charging source. Actually the generator battery has its own dedicated Prosport charger so there is redundancy. I also have a Prosport charger on the starter batteries. The only occasion I use the Blue Seas ACR is to combine the house and starter systems when dropping and raising the anchor. We then switch it back to the "off" position. Combining the batteries is probably not necessary but the windlass is a large Plath, so it's what we do.

Thanks Jim.

It does seem a little odd to me that my thruster/davit batteries are 2 x 8D Lifeline AGMs. That is over 500AH of batteries! They seem very happy however with the Duo-charger which tells me that they do not consistently ask for more than 30amps of charge. It may be possible that when both bow and stern thruster are being using a lot that the current draw is greater than the 30amps and the Duo Charge will stop sending charge to that bank. However, when done using the thrusters the bank must ask for less than 30amps since those batteries have always remained charged even though at times I have used the thrusters a LOT.

Of course, I just realized that I have absolutely no idea what battery is used to power the windlass. If I had to guess it would be the same bank that is used by the thrusters/davit.

For grins, I may change back to the Duo Charger for my start battery and see what happens. It is a simple change from the ACR as all the wiring is in place. If the Duo Charger is able to keep the engine start battery charged I see no reason to use the ACR instead of the Duo Charger. I do have a combining switch that will combine the 600AH house bank with the engine start battery if there is a problem with the start battery.

My guess is that I should probably look at installing some type of decent battery monitors. I have a monitor for the house bank, but nothing that I have found for any of the other batteries. Maybe I can do that when I install temperature sensors on the batteries.