Can I use a Battery Balancer on this 3X 24V LiFePo4 battery bank?

[pierreb]

This bank is set-up as 3 X 24V batteries connected in parallel. Each battery positive and negative is individually connected to the shunt. Those 3 batteries were all installed at the same time and each have their own internal BMS. Lengths of cable between batteries and shunt are all equal.

I have had issues where 1 or 2 of the batteries go inactive after a while, when that happens the 3rd battery remains active with the charge/discharge load. In a discharge scenario when I see this issue, the voltage on the active battery starts going down, while the 1 or 2 inactive batteries maintain their higher voltage, they are like sitting there in standby mode. I know this because I've been monitoring the current flowing in/out of the individual batteries, so easy to see when a battery goes inactive, all of the charge/discharge current going through the active battery/es.

Questions -- Would a battery balancer help keep those 3 batteries active and balanced? If not, any other ideas on how to fix this?

Thanks

 

[sunshine_eggo]

I don't see how. When you have batteries connected in parallel, they are always at nearly identical voltages. Battery balancers seek to equalize voltages... but they're already equalized.

If you're seeing voltage differences at the BMS, that means the batteries are completely isolated from the circuit, i.e., it doesn't matter what you put on the battery terminals, it can't do anything because the BMS won't let it.

Why do these batteries go inactive? Is it some BS feature of Renogy that they go dormant after 24 hours, or is there some other problem?

A battery "going inactive" is extremely atypical. Figuring out WHY this is happening is the way to solve the problem. You're taking aspirin for a sore arm when what you need to do is figure out your arm is broken, and put it in cast, i.e., treat the problem, not the symptom.

 

[TacomaJoe]

A work around might be a timer that loads the battery every 8 hours to keep them awake. Stupid yes but what else is there.

 

[pierreb]

I don't see how. When you have batteries connected in parallel, they are always at nearly identical voltages. Battery balancers seek to equalize voltages... but they're already equalized.

If you're seeing voltage differences at the BMS, that means the batteries are completely isolated from the circuit, i.e., it doesn't matter what you put on the battery terminals, it can't do anything because the BMS won't let it.

Why do these batteries go inactive? Is it some BS feature of Renogy that they go dormant after 24 hours, or is there some other problem?

A battery "going inactive" is extremely atypical. Figuring out WHY this is happening is the way to solve the problem. You're taking aspirin for a sore arm when what you need to do is figure out your arm is broken, and put it in cast, i.e., treat the problem, not the symptom.

Ok I understand, since they are dormant, nothing the balancer would do could make a difference, get it.
Those batteries are from Lithium Valley. Been asking the manufacturer for help, they first asked that I fully discharge them, then recharge together. which I tried that. They played well together for a while (~1 week), until 1 of them goes dormant. Other than that, they don't have anything else to offer.
As soon as I load them "seriously" those dormant come online, Serious load 150+ Amp. (typical load=5-10A
Is it possible that the load is too small for long periods for this large combined battery capacity?

 

[sunshine_eggo]

Ok I understand, since they are dormant, nothing the balancer would do could make a difference, get it.
Those batteries are from Lithium Valley. Been asking the manufacturer for help, they first asked that I fully discharge them, then recharge together. which I tried that. They played well together for a while (~1 week), until 1 of them goes dormant. Other than that, they don't have anything else to offer.
As soon as I load them "seriously" those dormant come online, Serious load 150+ Amp. (typical load=5-10A
Is it possible that the load is too small for long periods for this large combined battery capacity?

It sounds like they just have some undesirable "feature." Renogy has a battery that will go dormant after 24 hours and actually requires a charge to wake up. So stupid.

It sounds like the manufacturer is dealing with an unintended consequence of a feature that wasn't entirely thought through. I'd ask for a refund or replacement with batteries that don't screw with you.

 

[HarryN]

Interesting challenge.

I am guessing that the batteries go inactive to save on power consumed for the BMS and displays.

It would not "fix it", but if your goal is to spread the "use" around to all three, then one possibility is to put a switch or breaker in the line between each battery and the (+) bus bar. Sort of rotate usage around.