bluetrepidation
New Member
- Joined
- Jun 25, 2021
- Messages
- 16
Hello,
I have a 2p8s pack of 100Ah Fortune cells from Electric Car Parts Company. I've fully cycled the cells maybe 40 times. Recently I've noticed that I can't run my loads as long as in the past. When charging I noticed my BMS seems to be cutting off the pack early. So I decided to investigate with a multimeter and log the min/max voltages on particular cells. When charging at 70 amps (0.35 C) cells 8, 6, and 5 reach 3.6 volts well before the other cells. So I re balanced my pack twice and kept testing over the last two weeks. Then I noticed something that made my heart sink. When running a decent load of 90 amps (0.45 C) cells 8, 6 and 5 also sag in voltage. The cell imbalance on my BMS shoots up to 300 mA. To me this is a sign of high internal resistance. Any ides on what I should do? Or just call it a $2k loss and move on?
I've checked the following....
- Looked for loose connections between cells.
- Verified that my multimeter and the voltages displayed by my BMS matched and are accurate.
- Verified that my BMS cuts off discharge when any of the cells hit 2.5 volts.
- Verified that my BMS cuts off charge when any of the cells hit 3.6 volts.
- Max discharge the pack has been exposed to is 121 amps for 3 seconds averaging 11 amps over the long term.
- Max charge has been 70 amps.
Thanks,
A.J.
I have a 2p8s pack of 100Ah Fortune cells from Electric Car Parts Company. I've fully cycled the cells maybe 40 times. Recently I've noticed that I can't run my loads as long as in the past. When charging I noticed my BMS seems to be cutting off the pack early. So I decided to investigate with a multimeter and log the min/max voltages on particular cells. When charging at 70 amps (0.35 C) cells 8, 6, and 5 reach 3.6 volts well before the other cells. So I re balanced my pack twice and kept testing over the last two weeks. Then I noticed something that made my heart sink. When running a decent load of 90 amps (0.45 C) cells 8, 6 and 5 also sag in voltage. The cell imbalance on my BMS shoots up to 300 mA. To me this is a sign of high internal resistance. Any ides on what I should do? Or just call it a $2k loss and move on?
I've checked the following....
- Looked for loose connections between cells.
- Verified that my multimeter and the voltages displayed by my BMS matched and are accurate.
- Verified that my BMS cuts off discharge when any of the cells hit 2.5 volts.
- Verified that my BMS cuts off charge when any of the cells hit 3.6 volts.
- Max discharge the pack has been exposed to is 121 amps for 3 seconds averaging 11 amps over the long term.
- Max charge has been 70 amps.
Thanks,
A.J.