BBS02B 750w mysterious problem

Hi all,

my second bafang unit, since first was stolen. This one has been runnin about 10 months now. But not without problems.

ATM I get no power to pedals, no PAS no throttle. Nothing happens. But sometimes i get a minute or two or 10 minutes of power and suddenly it disappears again. I Get power to my display DPC-18. When i get power I only get 600w maximum. I wonder what happened to max over 1kw, what it used to give.

When i get no power, i still see battery voltage, but green battery logo on upper right corner is lost, showing nothing but black there. Also, when no power is given, speedometer does not work.

Any ideas? Battery is fully charged and voltage is around 58v. This is a great mystery.

I have not connected brakes on this system.

recheck all connections


correctly bypass display

jumpstart motor controller

works under throttle

or top pas level

may help

rule in out display


test health of battery pack

not only voltage

current under load

Yes, possibly a bad connection between the battery and the motor. If you hit a bump or something and briefly interrupt the battery connection, the controller will sense low voltage and stop. This kind of problem is not uncommon with removable batteries on a quick release cradle.

Ok, more info.

I just got programming cable. It connects to controller, reads it and writes it.

I just noted that it is showing red empty batttery indicator. I went through contacts, and now it is green and showing full and 57v voltage. Still no response on throttle or PAS.

and more,bypassing display puts speed sensors red light on, but no power.

No error messages on the display?

Not sure what you bypassed. Sounds like you found at least one problem.

Now no error messages on display. It used to get error 30..

but for now, what i mean by bypassing display, i unplugged it and hotwired cable from controller

That is pretty strange. Since you can get the LED on the speed sensor to light up, at least the 5v regulator is working. And since it still doesn't run with the display bypassed, it's not just a display problem.

I'd suggest opening the controller and take a look. Look for signs of water damage and re-seat all the connectors. Be sure to disconnect the battery and discharge the main caps first.

Yes its really weird. It acts like there was brake on all the time blocking power, but then again what explains that i got that weird batteryindicator.. And now battery indicator is fine. I put pics later

https://ibb.co/LZtd737
https://ibb.co/yR1gh3G

if jumping correctly

no pas or throttle action

inclined towards duff controller

or perhaps internal wiring

check moisture ingress

More diagnostics. I took controller of. Checked wiring. There was some tarnish on plug that has red black grey white. Tarnish was on red contact surface, both female and male sides.

I put it together, and after that i could run motor on throtle for around 1 minute under no load (as i tested it), and suddenly it stopped again. Nothing moved between these 2 stages. It just suddenly stopped giving power to gears. And now it is again "no power".

Could broken controller do this. Just stop suddenly working and then work again..?

https://www.youtube.com/watch?v=Dc5VwvFPa30 Managed to take some video. After video, throtle stopped responding again