150A version 6 or so BMS is giving me a bit of grief on my 48v 16s 280ah pack.
The unit has failed in the 2 or so years I've had it and 4 cell wires just stopped reading completely, and it was sent back for repairs (painful).
Since then it has mostly been "ok" but increasingly I am seeing 1 random cell (which changes until I "reset" it) starting to creep up high in voltage vs the rest, trip the HVD, drop back to same voltage as the rest of the cells instantly, then repeat. Especially prevalent on higher charge currents. I'd have thought if that cell was legitimately lower capacity/full it would not drop back to the same rest voltage as the others instantly, as this happens when the pack might be at 50%, not just near the top. Also, when this occurs the BMS SoC will jump from whatever it was, today 59%, straight to 100%, but the pack is still happily accepting charge as it's definitely not full.
To "fix" this, I have to turn the BMS off, I always double check the cell wire connection, remove/clean/retorque down etc and then suddenly that cell is perfect. A week or 2 later it's a different cell - repeat. The pack is also lightly compressed.
I have the balance function turn off, I use a 5a Heltech active balancer instead. I use the supplied busbars, single bar, studs into the cell terminals and nut/washer on top to ensure good connection. Have also tried copper grease to improve connection/reduce resistence.
I'd love to think it's as simple as a bad connection, but it's so consistent and the affected cell moves around. The cell wires are only crimped onto the ring terminals, but I've been over those and given them an extra crimp or 2 for good measure also.
Earlier today, pack lower capacity, charge power barely 1000w 1 cell was all over the shop, 3.3, 3.6v, later today, 2000w charging, that cell is still "high" but has settle way down and is not tripping the HVD anymore.Temp playing a factor? Balancer working hard? Still feels like a false positive?
Thoughts welcome, or suggestions on something better that's still common port also welcome.
The unit has failed in the 2 or so years I've had it and 4 cell wires just stopped reading completely, and it was sent back for repairs (painful).
Since then it has mostly been "ok" but increasingly I am seeing 1 random cell (which changes until I "reset" it) starting to creep up high in voltage vs the rest, trip the HVD, drop back to same voltage as the rest of the cells instantly, then repeat. Especially prevalent on higher charge currents. I'd have thought if that cell was legitimately lower capacity/full it would not drop back to the same rest voltage as the others instantly, as this happens when the pack might be at 50%, not just near the top. Also, when this occurs the BMS SoC will jump from whatever it was, today 59%, straight to 100%, but the pack is still happily accepting charge as it's definitely not full.
To "fix" this, I have to turn the BMS off, I always double check the cell wire connection, remove/clean/retorque down etc and then suddenly that cell is perfect. A week or 2 later it's a different cell - repeat. The pack is also lightly compressed.
I have the balance function turn off, I use a 5a Heltech active balancer instead. I use the supplied busbars, single bar, studs into the cell terminals and nut/washer on top to ensure good connection. Have also tried copper grease to improve connection/reduce resistence.
I'd love to think it's as simple as a bad connection, but it's so consistent and the affected cell moves around. The cell wires are only crimped onto the ring terminals, but I've been over those and given them an extra crimp or 2 for good measure also.
Earlier today, pack lower capacity, charge power barely 1000w 1 cell was all over the shop, 3.3, 3.6v, later today, 2000w charging, that cell is still "high" but has settle way down and is not tripping the HVD anymore.Temp playing a factor? Balancer working hard? Still feels like a false positive?
Thoughts welcome, or suggestions on something better that's still common port also welcome.
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