Ar you sure that keeping charger & BMS connected to even slightly unbalanced cells for a week might fix unbalance?
I got cells but keeping cells connected for days BMS does not balance them all equally - to 4.19v.
Battery pack 30Ah, 72v. Cells are in a good state but before stacking them to battery pack they were not charged up equally.
The BMS I'm using: https://goo.gl/cGZhWP
According to description BMS balance current is 50 mili amps.
The BMS does not balance cells even after a few days. After charger finishes charging, charger switches off / goes idle. Some LEDs stays for ten minutes or so, and then all LEDs one by one switch off. I doubt that BMS is doing anything to get cells equal charge ie discharge highest cells to be equal to lowest, and start whole battery pack charging again.
4,17
4,16
4,18
4,16
4,17
4,18
4,18
4,19
4,18
4,17
4,18
4,17
4,16
4,18
4,15
4,15
4,16
4,18
4,17
4,16
Later on these two cells with with 4.15v where charged up separately each; ~3Ah charged to each 4.15v till they
become 4.19v. After that regular 72v charger & BMS connected to the battery pack and it does not balance all 20 cells to 4.19v.
Will it be differently if I keep connected charger & BMS for weeks, I doubt.
I don't think that this BMS is faulty unless they are all faulty. I've tried few similar cheap BMS and they all do the same ie they do not balance.
At the beginning I was thinking that the BMS is discharging highest cells (when LEDs off) to be equal to lowest ones but after few days waiting I don't think so anymore.