[Request for advice] Looking for an appropriate charger

Not good news. Depending on the chemistry it shouldn't be lower than about double that. At 20V it's telling you that most of the cells are way below their spec'd minimum voltage or that one or more cells are dead. Low cell voltage can lead to early cell, and therefore, battery failure. Can't really say if that's all ready happened or not. You could take the pack apart and check individual cell voltages. If none are dead and you're willing to spend a few $ on the charger you can test the pack by charging it up. If the voltage comes up, you're good to go. Otherwise you've got a new charger and a dead battery.
Ok, thanks, I'll disassemble it and see.
 
I started disassembling the battery, but there were many little blocks to disassemble and I didn't think I would be able to put it all back together, so I went and bought a new battery and a charger for it at a local e-bike store.

Thread closed, I guess, thanks to everyone for the answers and help.
 

harryS

Well-Known Member
TC, did the shop sell you a battery that is the same as the original Jetson? Then you might be able recharge that with your new charger.

FYI. If the battery's BMS is working right, it isolates the internal cells from the battery terminals when they go below minimum voltage. Your 20V reading is just residual charge on the circuit. It's not measuring the cells. A 48V battery will show the true cell voltages down to about 40 volts. Any lower than that, the BMS shuts off the output, Then it's like what you see if your battery had an on/off switch and is switched off. It's just residual charge.

A lithium battery that really got to 20V would likely go up in flames if it were to be recharged.