Old eBike cutting power after 2 seconds, need help

My neighbor asked me to cleanup and sell their 2016 X-Treme Trail Maker e-bike. It appears to have been sitting through winter. The LifePo4 24v battery indicator shows full charge and reads 29.26v which held full charge overnight so far.

The motor will run fine with no load (wheel off the ground) but during a ride it will run 2 seconds and cut power. After turning ignition switch off/on it will do the same.

The 24v (model yk70b) controller has 4 wires coming from the controller that are unplugged. Two are red (male and female) and are both connected to the same black. Two are white, one male one female. Do we know what these are for? Should they be plugged in?

Could this be an unbalanced battery issue?

Yes, its a battery issue. Most likely the battery died during the winter. Lithium batteries need a top up on the charger about monthly all winter.

My guess, nobody told them that. We get this all spring, every year. Sellers need to tell the customers to top up a few times each winter. Many wont anyway, but it will at least help those who do listen.

Yeah that's what we're thinking, thanks Dan.

If you plug the battery pack in to the charger and leave it for days, the BMS system will balance the cells, but in this case that would be a long shot- the battery is probably toast. I would be interested in the old pack for parts if it is being sold off.

Lithium cells are generally VG about not self-discharging. Technically it is the drain of the BMS system which flattens them over a long storage period. Perhaps someday the switch on the battery box will be smart enough to kill the controller power when the battery is not in use. The only odd thing is that you would need to turn the output on in order for charging to work.

JBurdman7 said:

If you plug the battery pack in to the charger and leave it for days, the BMS system will balance the cells, but in this case that would be a long shot- the battery is probably toast. I would be interested in the old pack for parts if it is being sold off.

Lithium cells are generally VG about not self-discharging. Technically it is the drain of the BMS system which flattens them over a long storage period. Perhaps someday the switch on the battery box will be smart enough to kill the controller power when the battery is not in use. The only odd thing is that you would need to turn the output on in order for charging to work.

Click to expand...

More intelligent bms only balance above a threshold, and some cheap bms only balance while charging (active vs passive balancing).