ultimatenic
1 mW
I've been having some issues with my ebike battery. It is a 48V 15AH ping with high rated BMS (continuous discharge of 60amps). My bike is a 1500W and likely pulls 30-50AMP at full throttle. I've had the battery about 2-3 years and have always ridden full throttle, always.
The issue is that the low voltage cut off is being triggered due to voltage drop but through testing I have not been able to narrow down any low cell group. Basically I can run the bike motor at full throttle with no rider (back wheel propped up and wheel spinning freely). They second there is a rider on the bike at full throttle the battery cuts off within seconds. Plugging the battery back in for a second brings the system to life again. I've tested the battery within about 2 minutes after cut-off and all the cells read 3.4-3.5, so I cant narrow it down to one cell group over another. My theory is all the cells are degraded but just not showing so at rest.
I guess the most illuminating question for me is this: Is it possible for a degraded cell pack to read 3.5 volts per cell, and 56/58v for entire pack at rest (even after a cut-off)? Is it possible for the battery to still be able to output 20amps or 30amps but under full load(with a rider on the bike) pulling 50amps the battery just doesn't have it and it triggers the shut down? Is this behavior conducive with an aging LiFePO pack?
The other theory is that there is a fault on the BMS?
(PS I was able to test this battery on another bike and I saw the same behavior. Bike would run fine but at full throttle we saw voltage drop to below 48V triggering a shutdown. Then battery returned to nominal voltage of above 52V)
New Battery? More testing? BMS?
Any insight is greatly appreciated.
The issue is that the low voltage cut off is being triggered due to voltage drop but through testing I have not been able to narrow down any low cell group. Basically I can run the bike motor at full throttle with no rider (back wheel propped up and wheel spinning freely). They second there is a rider on the bike at full throttle the battery cuts off within seconds. Plugging the battery back in for a second brings the system to life again. I've tested the battery within about 2 minutes after cut-off and all the cells read 3.4-3.5, so I cant narrow it down to one cell group over another. My theory is all the cells are degraded but just not showing so at rest.
I guess the most illuminating question for me is this: Is it possible for a degraded cell pack to read 3.5 volts per cell, and 56/58v for entire pack at rest (even after a cut-off)? Is it possible for the battery to still be able to output 20amps or 30amps but under full load(with a rider on the bike) pulling 50amps the battery just doesn't have it and it triggers the shut down? Is this behavior conducive with an aging LiFePO pack?
The other theory is that there is a fault on the BMS?
(PS I was able to test this battery on another bike and I saw the same behavior. Bike would run fine but at full throttle we saw voltage drop to below 48V triggering a shutdown. Then battery returned to nominal voltage of above 52V)
New Battery? More testing? BMS?
Any insight is greatly appreciated.