Cell Failure or too impatient?

[randle p mcmurphy]

I've had 4 176ah cells for about 16 months, with an Overkill 4s BMS. Recently noticed that cells were far out of balance (battery shut down at about 50% power remaining). I'm attempting to start the top balance by bringing the lowest cell up to the highest (3.517v). The low cell has been:
4th 17h 3.316v
5th 06h 3.328v
5th 17h 3.349v
6th 06h 3.346v
All are resting voltages (haven't been charging overnight).

Should I keep trying to get this cell up, or is it just bad?

If it is bad, is there a way to reconfigure the pack/bms to utilize the remaining capacity?
If that is not possible, where can I find single cells? These were cells purchased thru a link on the mobile-solarpower.com site, BLS official store on alibaba:

Thanks.

 

[sunshine_eggo]

I've had 4 176ah cells for about 16 months, with an Overkill 4s BMS. Recently noticed that cells were far out of balance (battery shut down at about 50% power remaining). I'm attempting to start the top balance by bringing the lowest cell up to the highest (3.517v). The low cell has been:
4th 17h 3.316v
5th 06h 3.328v
5th 17h 3.349v
6th 06h 3.346v
All are resting voltages (haven't been charging overnight).

Should I keep trying to get this cell up, or is it just bad?

Unknown.

You haven't indicated how you are bringing that cell up.

Assuming it's 50% behind the others, divide 88Ah by your charge current. That's how many hours it will take to charge it. The voltage curve is very flat until it approaches near full, where the voltage then shoots way up, so the very slow increase in voltage through the bulk of charging is expected.

If it is bad, is there a way to reconfigure the pack/bms to utilize the remaining capacity?

No. Either the cells will work together to some degree, or they won't.

Setting the BMS to optimal balancing with balance above 3.40V, 20mV difference and during charge only will help maintain balance if the cells are healthy enough.

If that is not possible, where can I find single cells?

Probably the same place you bought the four.

Is this battery used regularly or was it allowed to sit for an extended period?