I have built an 8s2p 24v pack with SAB 60280 cells. I built two packs one works perfectly charges and discharges great and all cells stay together within .010v while charging and discharging.
The second pack will become unbalanced both charging and discharging by over 300mv differences. while discharging the cells. The values cell #4 will drop to 2.6v. While cell #1 3.258, Cell#2 3.207 cell# 3 3.113 while the cell#'s 5, 3.282 cell6, 3.282 cell#7 3.283 , cell# 8 3.276. So cell #4 lowest with Cell#7 highest. Cells number 1, 5,6,7,8 are all within .020 thats fine. Cells number 2 and 3, (2) 3.207 and (3) 3.113 are about .080 difference. So cells 3 and 4 are the worse with #4- 2.6 and #3 - 3.113. Does this mean cells 4 and 3 are the bad cells? I have discharged and re-charged the pack with same results.
When I built the pack , I charged all cells to 3.5v then put them in parelle for a week and let them sit. Then placed them in their final series parallel combination and fully charged them. I'm only getting 87ah from the 110ah pack and all cells are new.
How do I find the bad cell to replace? what type of test to determine the bad cells causing the imbalance? SHould I break the pack apart into two 8series packs to find which row has the bad cells? I'm using a BMS from overkill BMS for all my packs and the BMS are all the same in the program structure so I'm confident it's not a BMS issue. Need help on how to ID the bad cell to replace.
When charging cell #4 is always behind in the charging if that helps.
The second pack will become unbalanced both charging and discharging by over 300mv differences. while discharging the cells. The values cell #4 will drop to 2.6v. While cell #1 3.258, Cell#2 3.207 cell# 3 3.113 while the cell#'s 5, 3.282 cell6, 3.282 cell#7 3.283 , cell# 8 3.276. So cell #4 lowest with Cell#7 highest. Cells number 1, 5,6,7,8 are all within .020 thats fine. Cells number 2 and 3, (2) 3.207 and (3) 3.113 are about .080 difference. So cells 3 and 4 are the worse with #4- 2.6 and #3 - 3.113. Does this mean cells 4 and 3 are the bad cells? I have discharged and re-charged the pack with same results.
When I built the pack , I charged all cells to 3.5v then put them in parelle for a week and let them sit. Then placed them in their final series parallel combination and fully charged them. I'm only getting 87ah from the 110ah pack and all cells are new.
How do I find the bad cell to replace? what type of test to determine the bad cells causing the imbalance? SHould I break the pack apart into two 8series packs to find which row has the bad cells? I'm using a BMS from overkill BMS for all my packs and the BMS are all the same in the program structure so I'm confident it's not a BMS issue. Need help on how to ID the bad cell to replace.
When charging cell #4 is always behind in the charging if that helps.
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