Battery Question - Combiner with different types of batteries

Just helped a dock mate replace a group 31 starting battery on his new (to him) trawler. The house bank is a relatively new set of 4 trojan 6V's. The failed battery was installed in 2013. The new one tested out with a full charge at the store.

The two banks are on a Blue Sea combiner. The green "combined" light is on whenever the Heart inverter/charger is powered, or the alternator is running (single engine, Balmar 150A, externally regulated.)

It's now 6-7 hours after the install. The inverter is still showing "charging" at 13.8V, although the current is less than 1 amp to either bank. It never went to "accept" or "float."

As I understand it, the combiner connects the two banks whenever there's charging current, and disconnects them otherwise.

Is this a good thing? I was under the impression that two banks with different battery configurations shouldn't be charged together. Then again, with just a single engine, how else would you make sure both were charged while underway?

CaptTom said:

Just helped a dock mate replace a group 31 starting battery on his new (to him) trawler. The house bank is a relatively new set of 4 trojan 6V's. The failed battery was installed in 2013. The new one tested out with a full charge at the store.

The two banks are on a Blue Sea combiner. The green "combined" light is on whenever the Heart inverter/charger is powered, or the alternator is running (single engine, Balmar 150A, externally regulated.)

It's now 6-7 hours after the install. The inverter is still showing "charging" at 13.8V, although the current is less than 1 amp to either bank. It never went to "accept" or "float."

As I understand it, the combiner connects the two banks whenever there's charging current, and disconnects them otherwise.

Is this a good thing? I was under the impression that two banks with different battery configurations shouldn't be charged together. Then again, with just a single engine, how else would you make sure both were charged while underway?

Click to expand...

Tom, when you reference the Blue Seas combiner, is the product name 'ACR', Automatic Charging Relay?

I assume the Trojans are LA wet cells. What type of battery is the group 31? If the start battery is an AGM, my weak understanding is that is not ideal as both batteries (house and start) will be getting the same charge profile.

If it is an ACR, it will combine the batteries whenever it senses a terminal voltage greater than about 13.0v for a given period of time. The exact period of time varies with the terminal voltage. Then when the terminal voltage drops below a certain level, about 12.75v for a period of time, the ACR will disconnect the two batteries. Again, the length of time varies with the low voltage. I think mine is 30 seconds or less.

I don't believe this would have anything to do with the inverter not going to float. That is determined by the amount of charge that the battery banks are accepting isn't it?

I phoned Blue Seas on this question a number of years ago, and they didn't recommend combining batteries for charging purposes unless they were the same type of battery. At the time, I had put in 2 Group 24's for a start bank and Trojan 105's made up the house bank. They did not recommend combining different types of batteries in 2 different bank configurations particularly if the house bank was significantly discharged.

Jim

Could one of the electrics experts come in on the differences if any charging flooded LAs and AGMs? I had the impression the charge profiles were close, though charging both kinds at one time with one charger might raise different issues. I`m thinking of a boat with LAs for start and house, and hard to access AGM(s) for thrusters.

Both banks are wet LA. The difference is age and capacity. Obviously form factor, too.

Not sure about the Blue Sea combiner. Will dig through the manuals, and also see what happens underway today.

CaptTom said:

Just helped a dock mate replace a group 31 starting battery on his new (to him) trawler. The house bank is a relatively new set of 4 trojan 6V's. The failed battery was installed in 2013. The new one tested out with a full charge at the store.

Click to expand...

Keep in mind that most G-31 starting batteries are an inexpensive automotive grade battery with a "marine" sticker. The plates are thin, separators thin, very little room for shed sulfate to build up before an internal short occurs and the grids are very thin. They don't handle the vibration abuse a golf cart battery can. On some power boats & go fast flat bottomed racing sailboats, these starting batteries can suffer short lives due to plates cracking/fracturing with chunks of plate dropping to the bottom of the case & creating an internal short.. Starting batteries are also far too often installed in engine bays where temps can hoover far above where the battery would deliver a suitable life. Heck no battery should be installed in an engine bay, but boat builders could really care less about battery cycle life after it leaves their factory. If one must buy a G-31 flooded battery, even for starting, it is best to stick with the "deep cycle" version as they are slightly more ruggedly built. Course this is no guarantee and a G-24, 27 or 31 flooded battery is really not a "deep cycle" battery when compared to a golf cart battery. In my experience Crown, Trojan and US Battery all build a decent G-24, 27 or 31 "deep cycle" battery.

Also any battery manufacturer can have a bad one in the lot. The replaced G-31 could have just been the bad apple.

CaptTom said:

The two banks are on a Blue Sea combiner. The green "combined" light is on whenever the Heart inverter/charger is powered, or the alternator is running (single engine, Balmar 150A, externally regulated.)

Click to expand...

This is how a voltage sensing relay should work. It is really nothing more than an automated BOTH/PARALLEL device that either parallels or un-parallels the banks based on voltage levels.

Parallels @ 13.6V after 30 Seconds
Parallels @ 13.0V after 90 Seconds

Un-Parallels @ 12.35V after 10 Seconds
Un-Parallels @ 12.75V after 30 Seconds

CaptTom said:

It's now 6-7 hours after the install. The inverter is still showing "charging" at 13.8V, although the current is less than 1 amp to either bank. It never went to "accept" or "float."

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If that 13.8V is being held steady it is likely already in float. Float may also be being temp compensated up if the batteries are cool. That said if float is set for 13.8V, and there is no temp sensor, float is a bit high for the Trojan's, if this boat is dockside most of the time. Trojan wants to see 14.8V for absorption and 13.5V for float both of these temp compensated. Most older Heart I/C's only had dip switches for cool, warm etc. not a real temp sensor. If the unit is connected to a LINK remote then charge set points should be adjusted to suit the Trojan's.

CaptTom said:

As I understand it, the combiner connects the two banks whenever there's charging current, and disconnects them otherwise.

Click to expand...

Not on current, the ACR combines based on system voltage. As long as the batteries remain above 12.75V, and don't drop below that for more than 30 seconds, the batteries will be in parallel. 12.75V is right at the 100% SOC range for most lead acid batteries so you're not "discharging" in parallel just charging.

CaptTom said:

Is this a good thing? I was under the impression that two banks with different battery configurations shouldn't be charged together. Then again, with just a single engine, how else would you make sure both were charged while underway?

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Most 12V flooded batteries can be charged in parallel without any issue. The thing that matters is the recommended charging voltages. With system voltage at XX.XX the batteries on the charge bus will simply take the current that need at XX.XX volts and XX SOC. Heck even when an AGM and flooded batteries share the same charging profile there is really no big deal in charging using a voltage sensing relay.

The real problem in the industry are crappy so called "smart" chargers that do not allow users to properly configure them for manufacturer recommended charging voltages, lack temp compensation, used simple "egg timer" algorithms and do not allow absorption times to be modified.

One of the biggest issues surrounding VSR/ACR/Combiners is an incorrect installation for the application, which leads to relay cycling.

Any time you have a large deep cycle bank and a small start battery all charge sources (wind, solar, alternator, battery charger etc.) should feed directly to the house bank not the start battery. The prevents relay-cycling (the in-built delays do not always prevent this) and ensures the VSR/ACR/Combiner is passing the least amount of current across it at all times, a best practice.

BruceK said:

Could one of the electrics experts come in on the differences if any charging flooded LAs and AGMs? I had the impression the charge profiles were close, though charging both kinds at one time with one charger might raise different issues. I`m thinking of a boat with LAs for start and house, and hard to access AGM(s) for thrusters.

Click to expand...

They use different charging voltages in deep cycle format. If you go to the manufacturer's website, they will generally tell you what voltages they want the battery to be charged at for absorption and float. I'm sure there's some latitude on the voltage, but many chargers have you select the type of battery, so it's likely fairly significant if you're deep cycling the battery. It's probably much less significant for start only batteries.

IMO, battery combiners for different battery types with different purposes (house versus start) is just a bad idea as only one is going to be charged in the optimal way. If I were configuring two banks like that, I would charge the house bank and then use a a 12 volt to 12 volt charger to maintain the start battery.

Ted

CaptTom said:

Both banks are wet LA. The difference is age and capacity. Obviously form factor, too.

Not sure about the Blue Sea combiner. Will dig through the manuals, and also see what happens underway today.

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Tom, did you sit out the "weather" yesterday. It sure didn't amount to much at my house, but is typical of the weather false alarms we get too often here in East TN.

It was good meeting you guys. Thanks again for the meal and safe travels.


EDIT: I just spoke to Tom after seeing him running downriver in Chattanooga as I was crossing the Olgiati bridge (what are the odds?). Gorgeous day to be running the "Grand Canyon of the Tennessee River."

I installed an extra battery switch to take the combiner out of the system when desired..

I rarely use my start bank (2 31 case batteries), and almost exclusively on the 4 GC wet cells.

Heron said:

I installed an extra battery switch to take the combiner out of the system when desired..

Click to expand...

If you want to disable an ACR a simple on/off toggle switch or a contura switch etc., in the neg lead, will do just that.

CMS...Thanks for the very thorough writeup.

I think that there is much too much concern about charging house and starting battery systems with a combiner. First let's define the problem:

A combiner is typically a voltage sensitive relay that combines (connects together) two battery systems using relay contacts when the voltage of one system reaches about 13.0 volts. The concern is that one battery system, typically the house needs almost all of the charging current and that can lead to overcharging of the other system due to the high voltage needed to fully charge the house bank.

This is what i have on my boat: two 6V golf cart batteries for house use and one group 31 starting battery. Both systems use flooded cell batteries but only the house batteries have filler caps. The starting battery is sealed.

I also have an old gel cell group 27 genset starting battery connected through the Echo Charger feature of the Freedom.

When the house batteries are discharged significantly, when I plug in to shore power, my Freedom 20 inverter/charger goes through its typical three steps. The bulk takes about 30 minutes, the acceptance takes about an hour as the voltage rises to about 14.5 volts and then it switches to float.

During this period I close the battery switches so that both the house and starting batteries see the same charging voltage. This is similar to a battery combiner, but I do it manually.

The concern is that this 14.5 volts needed for full charging of the house battery system is also applied to the starting battery, which is fully charged long before it reaches that voltage. This can lead to gassing- disassociation of water in the electrolyte to hydrogen and oxygen. So how bad is this.

It might be bad if you were a full time cruiser and discharged your house batteries every night and recharged both systems with a genset or externally regulated alternator every day. in that case there are a couple of things you could do. I can't put my finger on it right now, but I have seen very smart ACRs that have a lower voltage output for the start battery. Another way is to buy starting batteries with filler caps so you can periodically add water if necessary. I believe that as long as you can deal with the electrolyte level, over charging FLA batteries is ok.

But for most of us, it is not a problem if you occasionally run your house batteries down and charge both systems up and let the voltage go up on your starting battery for an hour or less.

My sealed flooded cell group 31 starting battery is still going strong after three years of service. And back to the gel genset starting battery. It is now at least 6 and maybe 10 years old and is still going strong even though it is exposed to the wrong charging voltages.

David

CMS said:

If you want to disable an ACR a simple on/off toggle switch or a contura switch etc., in the neg lead, will do just that.

Click to expand...

I had thought that a BlueSeas ML-ACR could be disabled by using the manual switch on the top of it, ie turn it to the right and it will "lock" in the disabled position. However, I have done this on mine but every 10 minutes or so I here a "click" from back in the lazarette where it is located. I am bit confused by the ACR specifications but I am beginning to suspect that even when disabled, the ACR still "checks" the voltage and makes an attempt at combining.

Am I nuts or is this still happening with the switch in the locked off position?

BTW, I agree with Ken, thanks for the great explanation. I appreciate your participation.

dhays said:

I had thought that a BlueSeas ML-ACR could be disabled by using the manual switch on the top of it, ie turn it to the right and it will "lock" in the disabled position. However, I have done this on mine but every 10 minutes or so I here a "click" from back in the lazarette where it is located. I am bit confused by the ACR specifications but I am beginning to suspect that even when disabled, the ACR still "checks" the voltage and makes an attempt at combining.

Am I nuts or is this still happening with the switch in the locked off position?

BTW, I agree with Ken, thanks for the great explanation. I appreciate your participation.

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I installed one of these on my old sailboat. As I recall the relay continues to operate even with the battery switch turned off. That allows you to power down the boat but still have it charging batteries (both banks as needed.)

Richard

Britannia said:

I installed one of these on my old sailboat. As I recall the relay continues to operate even with the battery switch turned off. That allows you to power down the boat but still have it charging batteries (both banks as needed.)

Richard

Click to expand...

In this case I'm not talking about the battery switch, but the ACR that I have has a switch on the top that allows you to manually turn it on, off, or lock it off.

dhays said:

In this case I'm not talking about the battery switch, but the ACR that I have has a switch on the top that allows you to manually turn it on, off, or lock it off.

Click to expand...

Ok sorry - I misunderstood. I should have read your post more carefully!

Richard

CMS said:

If you want to disable an ACR a simple on/off toggle switch or a contura switch etc., in the neg lead, will do just that.

Click to expand...

I have a similar setup with my Yandina combiner.

I have a G31 start and a 6xGC house, all LAs. Each alternator charges one bank...port 55A to the G31 start and stbd 110A Balmar to the house. No load or charge sharing is normally needed there, but the option of charge sharing exists through the combiner. Any load sharing or battery isolation would be accomplished by two Perko battery switches located outside the ER and clearly labelled.

The single bank 55A shore charger is connected to the house bank and a switchable Yandina 160A combiner shares this charge with the start G31.

I have a STST switch installed in the helm header that connects the combiner green remote wire to ground. This allows me to remotely defeat the voltage sensing feature that combines the banks. I use this to prevent the banks from combining during heavy charging of the house bank, typically at anchor.

I could have installed a SPDT-center OFF switch to allow a manual ON position without regard to voltage sensing but I felt that would not be useful and could lead to an inadvertent combining of the banks if left in that position. I have not regretted this decision yet and suspect I won't.

Since the combiner switch is ON for defeat or OFF for combine, I installed the switch inverted so the functions ON/OFF would seem more logical...UP for COMBINE (ON), DOWN for ISOLATE (OFF). Here's my overhead switch panel.



Normally when I return to my slip, my house bank is at or near float stage. In this case I leave the boat in the slip with the combiner on to keep a float charge on the start battery. If the house bank is in absorption stage, I disable the combiner (switch down) to avoid overcharging the now-full start battery. It's fine without a charge for the week or so that I'll be away from the boat.

Looking good after 9 hours or so running. The "charge" indicator on the Heart Link eventually changed to "float" and I think everything is as happy as it's going to be, given that nothing's perfect. Sitting at anchor now, we'll see how everything looks in the AM.

Thanks to all who contributed, always good to learn more about batteries.

Yes, we delayed our start one day for the forecast potentially bad weather. Glad we did, the squall line that went through did quite a bit of damage around the marina, but luckily we came through it fine. Very nice ride down the Tennessee from Chattanooga, through two locks and to the anchorage at Raccoon Creek, which seems pretty nice.

Update:

The BlueSea ACR turns out to be causing problems charging on shore power or generator. The Heart Interface sees the (combined) bank as fully charged and goes to float very quickly, even if the house bank is down 150AH (as it was today.)

Pulling the negative lead from the ACR (there is no switch) solved the problem, but leaves the starting bank with no way to recharge.

Looking at the option of installing a manual switch. Or better yet, a relay off the engine power ("ignition") switch.

I disconnected my ACR and am using a Balmar Duocharger. It doesn't combine the banks but simply sends a charging current to the start battery when the voltage is high enough on the house back (as it when it is being charged).

It would be worth considering. Cost is about $250 and then you can just leave it on all the time.

The Blue Seas ACRs do need to have the ground opened when you are on shore power or generator. If you have the Blue Seas battery charger you can hook up the ACR to the charger and it will turn the ACRs off when using 120V charging. The problem is that Blus Seas doesn't make a very large charger. I think that 40 amps is their largest. I put a manual switch in my last boat to open the ground when on shore power.

Comodave said:

The Blue Seas ACRs do need to have the ground opened when you are on shore power or generator.

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Wait... What?

Edit... I just went and read the directions and the only mention of a switch on the negative wire was for long-term storage. I assume to stop the sensing system from trickling down you battery.

Please explain what you are talking about.

If you have 3 banks combined with 2 ACRs, if one bank is down and 2 are up to charge your battery charger will see the charged batteries and cut down on charging. Most smart chargers sense which bank is low and sends more amperage to the low bank. If they are combined with the ACRs the charger can't determine which bank is low. So you open the ground when you are on shore power and the ACRs do not combine the banks and your 120V charger will act normally. Their documentation does not address this instance well. I was wondering about it when I did my previous boat so I called Blue Seas and asked about it. They confirmed that the ground needed to be open when on shore power charging.

Comodave said:

If you have 3 banks combined with 2 ACRs, if one bank is down and 2 are up to charge your battery charger will see the charged batteries and cut down on charging. Most smart chargers sense which bank is low and sends more amperage to the low bank. If they are combined with the ACRs the charger can't determine which bank is low. So you open the ground when you are on shore power and the ACRs do not combine the banks and your 120V charger will act normally. Their documentation does not address this instance well. I was wondering about it when I did my previous boat so I called Blue Seas and asked about it. They confirmed that the ground needed to be open when on shore power charging.

Click to expand...

Got it... Certainly a very good argument for only having two banks and combine all three circuits of the charger to a single and full power output. That is the way mine is and why I didn't understand what you were talking about. All good.

I reviewed the instruction card (can't call it a manual) that came with the BlueSea ACR. It doesn't show a switch, but the diagrams are very simplistic. It shows an outboard for the engine.

I think this was an add-on totally separate from the otherwise decent inverter/charger/regulator install.

I'll recommend a switch or maybe a relay once the delivery is done. Thanks for all the help, I thought maybe I was missing something obvious.
My conclusion is that the combiner should be de-energized on shore or generator power. In other words, not all that user-friendly.

Useful discussion. For the past year I have been using the remote switches in the pilothouse to isolate the start batteries at anchor. Previously I just left on 'Auto', but I found that as loads came and went the battery switches would click on or off. Even though they are in the ER, the sound was load and annoying.

Then, after engine startup I would set the ACR's to Auto. It seems this is not a good idea as the start batteries wont be discharged much at all in comparison to the House bank. I may well have shortened the life of the start batteries. Next time I'm out and anchoring I'll check the voltages of each bank, and leave the ACR's in 'Manual' until the House bank is nearly charged or I'm only 30 minutes from arrival and engine shutdown.

Top row of switches are the RBS. Normally i leave them all on. Bottom row is the ACR - up is On, centre is Auto and down is manual.

Insequent said:

...It seems this is not a good idea as the start batteries wont be discharged much at all in comparison to the House bank. I may well have shortened the life of the start batteries....

Click to expand...

I suspect you're correct. I don't think it's a coincidence that the starting battery (see original post) had to be replaced on this boat. I suspect tying it with the 600+AH house bank during charging did it in. I did notice a couple of gallons of spare distilled water in the ER left by the PO.

I was hoping someone could explain it more scientifically, this is just my "gut" feeling at this point. But I trust the evidence of my own eyes.