Rescuing an 80 volt battery...

[julianthegypsy]

The charger accepting it, does not make it safe, you essentially bypassed a safety feature. Extreme care required, keep it quarantined while charging and after charging in a fire proof place.

It is likely the bad cells will discharge quicker or result in the pack becoming out of balance. I would be giving it some use and checking again in a few weeks time.

Example, a waterproof outdoor container, filled with sand, well away from building or vegetation. If it goes up in the night, no lasting damage will be caused.

Good advice. It had 75 volts in it when I put it in the charger and it took ten minutes to charge it completely. Nothing got hot while the individual cells were charging or when the whole thing was charging but I'll definitely be keeping an eye on it and storing it somewhere safe. We're still not sure why some cells drained while most were at full charge, it may be related to the transistors that divert current from fully charged cells when it was left for a long period, but I doubt we'll ever really find out.

 

[Ross365]

While the individual 18650 cells are fairly amenable to work with, if you see videos of Li-ion batteries burning, they are very scary indeed. More than any other battery in the past, they need the battery management system to be working perfectly, so sorting the battery doesn't just mean the cells, but the BMS too.

 

[julianthegypsy]

While the individual 18650 cells are fairly amenable to work with, if you see videos of Li-ion batteries burning, they are very scary indeed. More than any other battery in the past, they need the battery management system to be working perfectly, so sorting the battery doesn't just mean the cells, but the BMS too.

I'm guessing we'll see if the BMS is working fairly soon. I made the mistake of leaving the battery in the mower for too long over winter and I'm hoping that's what caused the problem. There were no obvious physical faults anywhere so fingers crossed.

 

[Ross365]

I don't have the mower yet, but I have Li-ion hedge trimmer and a strimmer and I like them very much indeed!

 

[julianthegypsy]

I don't have the mower yet, but I have Li-ion hedge trimmer and a strimmer and I like them very much indeed!

This mower has worked very well. We have a big untidy meadow of a lawn at the back and a small one at the front and it will do both on a single charge. Extraordinary really.