disconnecting and balancing batteries

[jessicadavis]

Hey there,

I've been having some trouble with my battery bank shutting off at night and SOK suggested the batteries (4x 100Ah 12V in 2S2P for 200Ah 24V) are likely out of balance. They recommended I get a victron battery balancer in the system which I just installed.

Two questions :

1. The victron battery balancer doesn't kick on until 27.3V is reached, which it hasn't yet (currently at 26.6V). Is there any way to get the voltage to increase aside from having a spectacularly clear sky at high noon?

2. I want to take the battery bank apart and charge each 12V battery individually from grid power just to kickstart the balancing process. Any advice for this process? It will be my first time taking apart the bank.
Also, thoughts on this charger? I'll be taking it to a friends house and using it with their AC power; I'm totally off-grid.

https://www.amazon.com/Lead-Acid-Portable-Maintainer-Desulfator-Motorcycle/dp/B09ZLD6RJ5/ref=sr_1_8?crid=24WL9OLQ6J00U&keywords=12v+LiFePO4+battery+charger&qid=1675380171&sprefix=12v+lifepo4+battery+charger%2Caps%2C208&sr=8-8&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc

Thanks so much in advance & apologies if these questions are too obvious - I'm very new to all this. There are more details about my system in my post history if you want to dig for more info but also you're welcome to ask directly

 

[sunshine_eggo]

Hello again.

With 400Ah of 12V, 20A charger may be a little slow.

What's the charge voltage on that charger?

 

[jessicadavis]

Hello again.

With 400Ah of 12V, 20A charger may be a little slow.

What's the charge voltage on that charger?

Hey! Not sure what you mean by the charge voltage - it plugs into AC and says a 12V 100Ah battery should take 3H - assume that's if starting from 0 SOC - which shouldn't be the case on mine

 

[sunshine_eggo]

Hey! Not sure what you mean by the charge voltage - it plugs into AC and says a 12V 100Ah battery should take 3H - assume that's if starting from 0 SOC - which shouldn't be the case on mine

It was meant to make a point. You need to charge the SOK batteries to a specific voltage for full charge, right?

Does that charger charge to the required voltage?

 

[sunshine_eggo]

Something like this that charges to 14.6V:

https://www.amazon.com/dp/B08Q3C8BYF

It's less versatile and a little lower current than the unit you linked, but you need a charger that you KNOW will hit 14.4-14.6V.

Edit: Found a 20A version:

https://www.amazon.com/dp/B08Q3NVBG3

 

[jessicadavis]

Something like this that charges to 14.6V:

https://www.amazon.com/dp/B08Q3C8BYF

It's less versatile and a little lower current than the unit you linked, but you need a charger that you KNOW will hit 14.4-14.6V.

Edit: Found a 20A version:

https://www.amazon.com/dp/B08Q3NVBG3

Wouldn't the first one have that capacity because its 12V/24V & therefore has internal capacity for at least 24V?

 

[sunshine_eggo]

Wouldn't the first one have that capacity because its 12V/24V & therefore has internal capacity for at least 24V?

12V/24V doesn't mean everything between 12V and 24V. It means 12V batteries and 24V batteries.

Again, you need to charge to 14.4-14.6V per SOK. Can you confirm with absolute certainty that the unit you linked charges to those levels?

 

[sunshine_eggo]

Assuming you do all of them in parallel at one time to reduce touch time, the charger (+) goes to the first battery and the charger (-) goes to the last battery... across the bank - hopefully like you have your 2S2P bank connected.

The charge is done when the batteries measure 14.4-14.6V or higher AT THE BATTERY TERMINALS for a full 2 hours.

 

[jessicadavis]

Assuming you do all of them in parallel at one time to reduce touch time, the charger (+) goes to the first battery and the charger (-) goes to the last battery... across the bank - hopefully like you have your 2S2P bank connected.

The charge is done when the batteries measure 14.4-14.6V or higher AT THE BATTERY TERMINALS for a full 2 hours.

I don't think I have the equipment available to link them all in parallel for the AC charge. Would need more cables, lugs etc. unless there's another (inexpensive) way. Was planning on 1 by 1

I don't see the capacity anywhere on the first charger's specs - ty for pointing it out!

 

[sunshine_eggo]

I don't think I have the equipment available to link them all in parallel for the AC charge. Would need more cables, lugs etc. unless there's another (inexpensive) way. Was planning on 1 by 1

With 2S2P, you should have enough cables to do at least two at a time.

I don't see the capacity anywhere on the first charger's specs - ty for pointing it out!

Capacity is different. That's how much the battery holds. You need to know the charge voltage.

 

[sunshine_eggo]

Something you might consider...

It seems like you don't have enough solar to reliably charge anyway. since you're 2S2P, you could potentially take half the bank over at a time leaving 2S running things while working on the other 2S at the friend's house.

 

[jessicadavis]

Something you might consider...

It seems like you don't have enough solar to reliably charge anyway. since you're 2S2P, you could potentially take half the bank over at a time leaving 2S running things while working on the other 2S at the friend's house.

That's def an interesting idea. I'd like to just knock it out all at once though. I should theoretically have enough solar ; 800W at 6 hrs should be 4800W (obviously unlikely optimal conditions). someone suggested in another thread that it's due to low sun horizon during winter ; my panels are mounted flat

 

[sunshine_eggo]

That's def an interesting idea. I'd like to just knock it out all at once though. I should theoretically have enough solar ; 800W at 6 hrs should be 4800W (obviously unlikely optimal conditions). someone suggested in another thread that it's due to low sun horizon during winter ; my panels are mounted flat

it's possible that you may be down for SEVERAL hours. I was just thinking of a way to allow you to continue to operate the system. Having a smaller battery means the 2S string remaining might get fully charged and require very little charging individually.

 

[jessicadavis]

it's possible that you may be down for SEVERAL hours. I was just thinking of a way to allow you to continue to operate the system. Having a smaller battery means the 2S string remaining might get fully charged and require very little charging individually.

Forsure. I'll see what makes sense - do you have any thoughts on the first question at the top of the thread? & assuming you have lots of experiences with solar, is it typical for people to need to break down their banks and charge individually as a kind of ongoing maintenance?

 

[sunshine_eggo]

Forsure. I'll see what makes sense - do you have any thoughts on the first question at the top of the thread? & assuming you have lots of experiences with solar, is it typical for people to need to break down their banks and charge individually as a kind of ongoing maintenance?

I gave my opinion on the Victron balancers in your other thread.

Manually charging your batteries should allow them meet or exceed the minimum voltage required to start balancing. Hopefully, the victron balancers can maintain them moving forward.

Healthy batteries that are REGULARLY charged to full should stay in balance and not need individual charging. The individual/parallel charging of the 12V need to be done before they are wired in series for 24 or 48V. They do not ship fully charged and even small deviations in the charge can cause notable deviations.

 

[toms]

Rather than the balancer, I’d reconfigure the PV to have a 12V SCC for each battery.

That way it doesn’t matter if the batteries go out of balance.

 

[jessicadavis]

Rather than the balancer, I’d reconfigure the PV to have a 12V SCC for each battery.

That way it doesn’t matter if the batteries go out of balance.

Sorry, I don't quite follow this suggestion. Can you elaborate?

 

[jessicadavis]

I gave my opinion on the Victron balancers in your other thread.

Manually charging your batteries should allow them meet or exceed the minimum voltage required to start balancing. Hopefully, the victron balancers can maintain them moving forward.

Healthy batteries that are REGULARLY charged to full should stay in balance and not need individual charging. The individual/parallel charging of the 12V need to be done before they are wired in series for 24 or 48V. They do not ship fully charged and even small deviations in the charge can cause notable deviations.

I think this is where I messed up. I should have charged them to full using AC power before hooking them up in teh system. I made the misguided assumption they were likely all charged up from the factory I hope this misstep didn't drastically mess with the lifespan

 

[sunshine_eggo]

I think this is where I messed up. I should have charged them to full using AC power before hooking them up in teh system. I made the misguided assumption they were likely all charged up from the factory

Hazmat regs require that they ship at or below 30%.

I hope this misstep didn't drastically mess with the lifespan

Nope. Just annoying as hell for you in operation. Once you get the 12V individually charged to full, you'll likely have trouble free operation.

 

[jessicadavis]

Hazmat regs require that they ship at or below 30%.



Nope. Just annoying as hell for you in operation. Once you get the 12V individually charged to full, you'll likely have trouble free operation.

30%???? GASP