Bafang bbs02 problem

[Acho123]

Hello, two days ago i built my first ebike with a Bafang bbs02 750w mid drive motor and a custom 13s5p battery with 50A cont BMS.
It was workings wonderfully these two days and ive drove more than 40kms without any problems whatsoever. Yesterday was my first battery charging, everything went smoothly and with no heating on any parts.
Today i went out and drove around my town with normal speed and low gear ratio. I even stopped several times to check for any warm parts or mechanical faults, but there were no such things.
The problem stared when i stopped to make a call, i was at PAS 2 and i think the lowest gear possible, the call went on for around 10 min. The motor has switched off because the 5 min timeout has passed, so when it was time to go i powered the motor and....nothing happened, not even a flash.
I tried unplugging the display, the main cable with all the connections but with no avail.
I got home with pedalling and removed the heat shrink from the battery connection and unplugged the battery. When plugged in it made the normal spark and the motor turned on. I was happy and turned around so i can leave my tools and the moment i looked back at it it was already dead again. I did the unplug/wait/plug procedure several times and the display just flashed for 5 sec and went dead again. I measured the battery with my multimeter and the voltage was normal, i then pluged everything again and probed the connection between the battery and the motor. The voltage wasn't 50v but 30v and slowly climbing, after 7 min the voltage was around 48v and after powering it up it went down to 0.
One strange thing i noticed was that the bms was heating up without it actually doing something.

Is the problem bms related or is it the motor controller?

Thanks in advance!

 

[docw009]

Could be your BMS. I installed one over the winter and tested it with a hair dryer. Worked fine at 5A. First time on the bike, it went chugga chugga and blew up. Well past the aliexpress warranty by the time I found out. Lost $20.

Check the voltage on the cells. Make sure than none of the 13 cell groups is undervoltage and making the BMS shut off. If they're all at a normal charge level, you could temporarily bypass the BMS (run the controller wires right off the +/- terminals) just to show that the controller works. If it does run, this says your BMS is bad.

 

[Acho123]

Update:
Just found the problem. I took out the battery and saw two holes on the bottom of the heat shrink caused by the screws holding the box onto the frame. Two of the balancing wires were cut in half. After bridging them together everything works fine.
So problem solved