Balancing Epoch B48100A batteries?

[jdege]

I have pair of Epoch B48100A batteries, driving a pair of Elco EP9.9 outboards, on my boat.

These are 48V 100AH marine batteries.

I did a range test, the other day, running on motor on one battery, to see how far I could go.

The battery shutdown after about 70AH, throwing a cell under voltage warning. And checking the cell levels in the app, yes, one cell was very low.

All the cells except one were between 3.288 and 3.291V. That one was at 2.809V.

After plugging into shore power, I put the battery on its 20A AC charger. After a night on the charger with no load, the battery was full.

But the cells weren't very balanced.

All the cells but two were between 3.336 and 3.356V.

The one that had been low was still relatively low, at 3.302, and one cell was relatively high, at 3.374V.

VDIFF when the undervolt error triggered was 0.482V, which AIUI is quite reasonably a reason to shutdown.

But after the charge, VDIFF was 0.072V. A lot better, but not where it should be.

Should I be balancing this battery?

Does anyone know how to balance an Epoch B48100A?

 

[HRTKD]

The key to balancing cells is to not charge to 3.65 volts per cell. Try charging to 3.5 volts and use lower current at first. This gives the BMS more time to balance the problem cell(s).

Many BMS will not initiate balancing below cell voltage of 3.4 volts. Your "charged" cell voltages tell me that the BMS may not have had the opportunity to actually balance the cells. You need to charger higher. Maybe you need a better charger.

 

[jdege]

I've been using the 20A charger that Epoch sells for use with their B48100A battery. It has a communication link between the charger and the battery, and if it had been designed the way I would have designed it, the charger would have recognized the imbalance and done a top balance.

But if pigs had wings...

I have a bench top power supply that will provide up to 60V at up to 5A. It should work.