Help troubleshooting odd ebike power issue

Joined
Aug 17, 2015
Messages
11
Location
Claremont, California
Wondered if any of you have experienced this.

My bike developed this issue and I cant figure out if the battery has lost capacity or my motor controller or BMS is burned out or what.

I have a 48V 15ah ping battery. It's about 3-4 years old. Last winter temperatures got really low and battery wouldn't charge. After that cold snap the battery charged up but I've had this issue:

I charge battery. I disconnect and test bike, lifting the back tire and running the motor. Everything works. Wheel spins and full power levels.

But then if I hope on bike and if bike is on high power it cuts out the second I hit throttle. If I put the bike on lowest setting I can cruise down the block but on the way back it cuts out. Bike is unresponsive.

If I then take bike back to charger and just plug it in. It turns on. I can disconnect and run motor. Everything works. But when I jump on, again it doesn't last more than 30 seconds on the road.

Battery readings show 50-57 volts. And all battery series look like they are charged and holding charge (Though I had a funny reading that should one of the packs was 0 but then it was fully charged)

My theory is that battery cells are depleted enough that though they hold charge and power the bike. The second weight is added and the motor pulls higher volts the battery cuts out. Or my BMS is failing and cutting out when more volts are pulled...or my motor controller?

Thank you for any insight our ideas you may have.
 
What is the voltage when it cuts out, *after* the cutout, before it lets you start up again? If it drops to something ridiculously low, then the BMS is shutting off to protect the pack.

If the pack ever got really low, it probably needs to sit on the charger for at least several days to let it re-balance itself. If you just take it off when the charger first shows "green", then it never gets a chance to balance. It can take days (or more) if the cells differ greatly in voltage, because the BMS is only intended to fix small differences during a normal charge cycle.

If you are curious you can open up the pack and measure the voltages at the cell sense wires, both before and after charging. There are numerous battery repair threads (and similar threads to this one) which discuss and show how to do that.
 
I helped a friend who had a very similar problem. Everything seemed to test out fine but the motor would cut out on any kind of decent load. So we suspected the controller first, and then the battery. But in the end it came down to a corroded wire connection (it had apparently gotten wet and the copper was corroded under the heat shrink wrap). I replaced the wire and all was fine. So with a bike with many years on it, this may be something to investigate.
 
Thank you everyone. Yes so far I've searched the bike for shorts or bad wires. Everything looks good. I've also tested the voltage of the pack and the cells in the pack. Voltage always looks good before and after incident but a few of my cells are underperforming big time and the pack is not balanced properly. It's a pingbattery and Ping Li has been very helpful troubleshooting. I'm going to try and charge the underperforming cells manually to 100% then connect everything again and put the battery to charge and balance. Will update the thread with my findings.
 
The bad connector my friend had also "looked good" - that is until I actually cut off the heat shrink wrap for the connector and saw all the green copper corrosion. Static voltage tested fine as well.
 
Ping batteries need to be left on the charger for a long time so the BMS can balance the pack. The charger will cycle on and off numerous times during the balancing stage as the BMS drains a little out of the highest voltage cells, so the low voltage cells can be brought up to full voltage. If you failed to charge in this manner during the life of the pack, then the lowest cells probably reached quite low voltages and were damaged.

The first thing I'd try is to leave it on the charger overnight or longer, and then give it a go. If there are no weak connections causing the cutout, then it's like the BMS tripping due to one or more cells hitting the low voltage cutoff under load. If giving the pack a chance to fully balance doesn't help, then it's time for a new battery or a repair of the old one.
 
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