Dead battery pack

[destructimo]

Hi All,

I hadn't used the bike for a while and stupidly left the battery in it and the battery switched on (not the whole bike).

The bike wouldn't power on and the battery wouldn't hold a charge. Around 2.6V ish on the output.

I did try bump starting the BMS with a quick charge through the output of the battery and it did charge to 41V. I didn't have time to test it on the bike and it soon dropped out again (2.65V on the output again).

I guessed the BMS was dead so I ordered a new one which I fitted today. Plugged it in and it was charging. Success I thought. Charging stopped after about 30 minutes and again down to 2.65V on the output.

With the new BMS with it's larger connector I could actually probe the voltages of the cell groups of the 10S 36V pack.

The results between the pins are:
1
4.16V
2
3.80V
3
3.75V
4
.741V
5
.753V
6
.736V
7
3.80V
8
2.96V
9
4.15V
10
1.271V
11

Rightly or wrongly, I've rigged up a trickle charger via the balance plug, delivering 1A / 4.2V to see if the dead cell groups can be coaxed back into life.

Any thoughts?

 

[Nealh]

Yes, the battery is trash now.
You have four cell groups below 2v, anything that self discharges that low is not to be trusted.

Trying yo recover low cells at about 2.5v -2.8v is possible and within manufacturers specs but at low V's some of yours are well outside and will likely suffer from very high resistance, sag and capacity loss.
Even 1a is a bit high and you should be looking at a lower trickle something like 300/400ma until cells are above 3v, I wouldn't trust the battery now.

 

[destructimo]

No it's not looking too clever and charging the individual groups gets up to around 3V and then decays with the charger still connected.

I suspect more is going on so I have boxed it up and sent it off to Insat for a proper repair.


Thanks

 

[Nealh]

Beyone repairJimmy will strip it out and recell.