New cells seem out of balance

[loverofpeace]

This is after top balancing using wills method, and about 24hrs in parallel. Now hooked up in series. Could it be that they are grade B cells? Some of the terminals looked scratched up when they arrived.

 

[loverofpeace]

 

[loverofpeace]

 

[Pierre]

The cells delta is only 78mV. Should get better after a few cycles. Also check your cells delta setting in the balance parameter. There you can set it as well as when it should balance. You will also find that the cells start drifting apart when approaching the ’knees’ on the discharge curve.

 

[loverofpeace]

The cells delta is only 78mV. Should get better after a few cycles. Also check your cells delta setting in the balance parameter. There you can set it as well as when it should balance. You will also find that the cells start drifting apart when approaching the ’knees’ on the discharge curve.

Thanks Pierre! Was starting to freak out a bit here

 

[mandrews44]

This is after top balancing using wills method, and about 24hrs in parallel. Now hooked up in series. Could it be that they are grade B cells? Some of the terminals looked scratched up when they arrived.

All batteries I've touched so far will be further out of balance over 3.4 than once you start using them. After applying a load, they almost immediately drop into a delta of 0.003v. also, that BMS defaults for % charged needs some realistic adjustments and can't be used out of the box. Do a cycle to 13.1 / 13.0 (12v) and you will notice a big difference.

 

[tictag]

I would be interested to hear about your results after cycling. I'm personally struggling to understand why after balancing they would be any different at all.

I personally would be considering a full discharge test on cell if I had found this level of terminal voltage discrepancy.

 

[mandrews44]

I would be interested to hear about your results after cycling. I'm personally struggling to understand why after balancing they would be any different at all.

I personally would be considering a full discharge test on cell if I had found this level of terminal voltage discrepancy.

After 2 weeks cycling from 100% to 50% over 2 days to 90% to ~65% daily cycle, the new 2 packs delta is 0.002v without balancers or balancing of any kind. The two ShunBin batteries are 0.002 and 0.020. Each are approximately 400ah with a total usable capacity of about 17kw. I've recorded as much as a 10kw during my tests after building / installing the new cells and changing the BMS on the ShunBin packs.