What e-bike BMSs lack balancing? My Radmission cost $500 new. If the BMS didn't balance, two years of differing cell self-discharge would have greatly reduced my range. According to my log, it's the same as it was new.
Radpower's balancing instructions were the same as for my Radrunner in 2020. Leave the charger on 12 hours. Ride even a short distance. Leave it on another 12 hours. Ride again. Leave it on 12 hours a third time.
It said you would need to do the balancing process again someday but didn't say when. That was daffy to me, so used a watt meter. I think it was in 2023 that Radpower's instructions changed, saying to turn off the charger as soon as the green light showed, and no other balancing was necessary.
I think that came from their legal team as charging 12 hours would entail leaving it unattended.
I didn’t understand when you said passive balancing can continue briefly after the charger is removed. Now I see, thank’s to
@PCeBiker 's chart. Suppose the MOSFET trips when source-drain voltage is exactly 4.20. Source-drain voltage will immediately drop by the product of resistance and bypass current. It will switch off and on. With a voltage slightly over 4.20, the cell will trickle charge. When the charger is removed, the gate will continue to switch on and off until the cell voltage is down to 4.20.
That can explain what I've observed. Suppose the BMS will shut off charging current at 54.6 V (13 cells x 4.20 V.) Suppose 1 cell is undercharged, and trickle charging has brought the other 12 to 4.28 V. The BMS will stop charging when the low cell is at 3.48. After the current is shut off, battery voltage will drop as the 12 overcharged cells come down to 4.20. If the BMS shuts off, that will turn the charger light green and my AC meter will show a watt or less. If I give the charged cells an hour to come down to 4.20 and then turn on the charger, a current draw will show that there are still cells that aren't fully charged.
When this happens, the charging light may be red or green, depending on how much current the BMS is drawing.
