My Ebike uses a 70 pack of batteries 18650, 10 in series to make 42 volts with 7 parallel batteries per series. One parallel row registers zero volts after a winter of not being charged, I also suspect that the motor control has a small drain even with the key on the off position.
And I'll be attempting to get that row to hold a charge again.
I've seen tutorials where you can take a dead 18650 battery and make it able to take a charge by jump starting it with a good 18650 battery by parallel charging.
Since the batteries are spot welded I will disconnect the BMS(battery management system) and try to parallel charge a parallel row with good 18650 batteries.
But I seen it done with a 1 good to 1 dead set up but can I do that with multiple parallel batteries? Or is that dangerous or even pointless?
If all goes well every row will have a charge to give the BMS the input it needs to charge the pack and see if it works.
[UPDATE] I tried this setup and the wires were getting (can't hold on to them) hot. The volt meter when charging reads .7 volts still not getting a reading after 4 * 10 second charges.
Batteries stay cool on both sides tho.
If all fails I will have to tear apart the row and figure how to safely solder them back together.