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Old 02-23-2021, 12:00 AM   #1
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Equalizing two battery banks

I've rummaged around that inter-web thingy a bit and can't find if it's possible to equalize two battery banks at the same time. Something tells me you shouldn't, or can't, but maybe someone here knows for sure?

We have four flooded 6 volt golf cart batteries in series parallel and a flooded 4D starting battery.

Can you equalize them at the same time, or is that asking for all kinds of crazy psycho physics chain reaction thermo plasma shredding trouble?

Should the golf cart batteries be equalized, then the 4D separately?
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Old 02-23-2021, 01:06 AM   #2
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It's kind of like mixing your bar drinks. Then you don't know which one made you sick.

Since equalizing is an uncontrolled constant voltage charge, you should be able to equalize parallel banks, if the recommended voltages and times are the same. But like bar drinks, personally I'd do one at a time so if there are exceptions I'd have a clue why.
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Old 02-23-2021, 01:27 AM   #3
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It's kind of like mixing your bar drinks. Then you don't know which one made you sick.

Since equalizing is an uncontrolled constant voltage charge, you should be able to equalize parallel banks, if the recommended voltages and times are the same. But like bar drinks, personally I'd do one at a time so if there are exceptions I'd have a clue why.
Yeah, I've never done it before so probably not a good idea to mix it up. It'll be stressful enough without overcomplicating things
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Old 02-23-2021, 01:37 AM   #4
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I tried to find it, as I did read some where NO you should not. Mostly find not recommended to charge different types of batteries or different brands of the same ah together. So it stands to reason you should not try to equalize two different types.

Also do it in a well ventilated area wearing goggles, topping up fluid checking with hydrometer. and wear old clothes keeps coming up do to the mist of acid in the air.

I know I will not press the equal button any time soon on my charger
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Old 02-23-2021, 01:50 AM   #5
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Thanks, and yes, will definitely be reading up and getting my A game ready for this process before starting!
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Old 02-23-2021, 09:00 AM   #6
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Here's a related question. When equalizing batteries that also have batteries that are charged through an ACR, should the ACR be disabled?
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Old 02-23-2021, 09:13 AM   #7
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Depends, are the banks each on a different leg of the same charger? (i.e, a "two bank" charger). One would hope so if they are different battery types. So yes, disconnect the ACR.

Read the charger manual!!
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Old 02-23-2021, 09:21 AM   #8
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In equalizing you raise the voltage so the electrolyte is gassing. This agitates the electrolyte and causes precipitated lead sulfate to go back into solution, avoiding loss of capacity and possible plate shorting if it is left sitting on the bottom.

That takes a fair amount of current for a big battery bank. So I would prefer to do them individually so you can get the maximum effect on each bank.

That begs the question: how much current is necessary and how long. I don't really know, but I would monitor the electrolyte level while equalizing. At first it will go up because of the gas produced. Then it will start to go down. That is when I would stop.

And a confession- The foregoing is entirely theoretical (well the part about electrolyte level going up and down), I have never done it.

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Old 02-23-2021, 09:45 AM   #9
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One of the nice things about a Smart ACR, it would auto disconnect from the house bank during the equalizing process.
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Old 02-23-2021, 09:53 AM   #10
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I would do them separately mostly because as different battery types they are likely to require different amounts of equalization.


You will experience crazy psycho physics chain reactions, but no thermo plasma shredding.


As you equalize, monitor battery temp and electrolyte level. Also be sure the area is well ventilated, and free of anything that might spark like a light switch. You will be off-gassing hydrogen which is highly explosive.



I find it's convenient to eq in 1 hour sessions. That helps keep temps from rising too much, and let's you check the specific gravity with a hydrometer after each session. The goal is to get the SG back in spec. Your initial readings will tell you how far off you are to begin with. Keep the fluid level above the plates, but not full since the EQ will cause bubbling and spill.



Be sure the have the manufacturer's specs on hand for fully charged SG. Typical would be 1.260. And also the EQ voltage. Also be sure to adjust the SG readings based on the electrolyte temp. 1.260 would be for 25C, but after an EQ session your temps will be higher.
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Old 02-23-2021, 11:20 AM   #11
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Quote:
Originally Posted by Soo-Valley View Post
I tried to find it, as I did read some where NO you should not. Mostly find not recommended to charge different types of batteries or different brands of the same ah together. So it stands to reason you should not try to equalize two different types.
Charging is a voltage and current regulated process, no way on parallel banks to determine or control which bank the current is headed. Equalization is a fixed voltage overcharge, if charge capacity is sufficient there is no need to know where the current is going so parallel or not doesn't matter. In theory.

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Here's a related question. When equalizing batteries that also have batteries that are charged through an ACR, should the ACR be disabled?
Many ACRs (most of the Blue Seas ones for example) have a high voltage disconnect and may disconnect themselves at equalizing voltages. So without looking at the documentation for your particular model, you can't depend on the ACR either way.
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Old 02-23-2021, 12:54 PM   #12
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Murray,
I am with the others. Do the batteries (banks) separately. When putting a bank together, the experts always recommend using the same brand, size, age, batch, etc. of batteries and DO NOT MIX. Probably if a person were totally an-l, they would equalize each battery in a bank separately, but I have not done that or heard that any gain is worth the effort.
I equalize my FLA (6 golf cart) house bank 2 times per year. Once in the fall before "putting the boat to bed" for the winter. Start with the bank fully charged, with the fluid level well above the plates. I turn off all 12V loads (including ER lights) and monitor the batteries throughout the (usually) 3 hour process. I have solar so the batteries are fully charged all winter. I do not use the solar for equalizing. In the spring, to prepare them for "battle", I equalize them again, but this time only for about 1 hour. To ventilate I leave most windows and doors open and run a 120V fan in the ER (batteries are in ER) to blow fumes out the ER vents. Definitely take precautions (like glasses, old clothes, ventilate, etc.) but it is not that scary to do.

Most of what I do when it comes to batteries, I have learned from Rod on marinehowto.com.
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