So here's my current working theory on battery fires. I get the "cheap" battery with no BMS or thermal cutout, OK. But:
Batteries have VOLTAGE and CURRENT. Most ebike batteries are 36, 48, or 52 volts. But as the battery is drained by riding, the voltage drops, and the controller / BMS has to supply more current to keep a constant level of power to the motor. That increases the battery temperature.
Make sense so far, right ?
So at very low voltage levels, if the battery is drained to say 10 % and then you put it on the charger and leave it powered on, that could cause a thermal runaway resulting in a fire.
I seldom drain my bike's battery below 20% and I don't leave it charging unattended. The charger gets noticeably warm but I keep an eye on it.
if you leave a battery charging unattended and plugged into a power strip with crappy / old house wiring, or overloaded outlets, then all bets are off.
"UL Approved" won't solve that problem. I'm thinking too of that auto transporter that sank off portugal last year taking 100s of electric Porsches and mercedes with it. What do you suppose happened there ?
I think somebody got in a car to listen to the radio or turn on the heated seats, got out and left the power on.
anyway that's my theory ! I'm sure I'll get "flamed" in the responses.
/markp
