Hi there,
I have a 10s2p battery without hard case (just shrink wrap). I dropped it, and now the negative terminal of one of the cells in the last pair on the positive end of the battery is dented. Photo attached.
I first noticed an issue when the battery voltage was suddenly so low that my ebike wouldn't even turn on. Multimeter said 24v.
I charged it up again, and it got back up to 42v like it should, but over night it dropped back down to 38v.
I unwrapped the battery, noticed the dent.
I tested each pair, working my way up from the negative end to the positive end. Except for the last parallel pair (positive end), every pair reads 4.14v +/- 0.01v; the last pair reads 0v. So it seems the cells are well balanced, but the last pair is defective.
Here's what I think happened, I'd just like you all to confirm:
- The dented cell is internally shorted out
- It self-drains to zero
- It's parallel neighbor then discharges into the dented cell until it also reaches zero
- When I charge it up to 42v, I'm only charging the non-dented cell in the pair, and as soon as I take it off the charger, they dented one discharges the non-dented one again.
Is that about right?
Follow-up questions:
- Do I only need to replace the dented cell? Or is the other cell in the pair damaged too by virtue of being discharged to zero?
- Is the battery safe to let sit like this, with the final cell pair at 0v? It should just be a 9s2p battery now, right?
- Why didn't I notice any kind of heat / get a battery fire if one cell is shorted out. Wouldn't that cause really high current?
Thanks!
I have a 10s2p battery without hard case (just shrink wrap). I dropped it, and now the negative terminal of one of the cells in the last pair on the positive end of the battery is dented. Photo attached.
I first noticed an issue when the battery voltage was suddenly so low that my ebike wouldn't even turn on. Multimeter said 24v.
I charged it up again, and it got back up to 42v like it should, but over night it dropped back down to 38v.
I unwrapped the battery, noticed the dent.
I tested each pair, working my way up from the negative end to the positive end. Except for the last parallel pair (positive end), every pair reads 4.14v +/- 0.01v; the last pair reads 0v. So it seems the cells are well balanced, but the last pair is defective.
Here's what I think happened, I'd just like you all to confirm:
- The dented cell is internally shorted out
- It self-drains to zero
- It's parallel neighbor then discharges into the dented cell until it also reaches zero
- When I charge it up to 42v, I'm only charging the non-dented cell in the pair, and as soon as I take it off the charger, they dented one discharges the non-dented one again.
Is that about right?
Follow-up questions:
- Do I only need to replace the dented cell? Or is the other cell in the pair damaged too by virtue of being discharged to zero?
- Is the battery safe to let sit like this, with the final cell pair at 0v? It should just be a 9s2p battery now, right?
- Why didn't I notice any kind of heat / get a battery fire if one cell is shorted out. Wouldn't that cause really high current?
Thanks!