5k miles Rear Wheel Hub motor stalls a lot and runs in reverse


10 kW
Mar 25, 2021
My hub motor was working great for about 5k miles. Then I suddenly started having problems. I will send input from the throttle and it will stall. Then it will spin in reverse. It was working fine until a couple days ago. IT feels like the phase sensors are having difficulty trying to figure out which is the proper way to spin. Also the halls no longer work but using a meter detects proper voltage. Halls are fine, just not being used. It might be that I have a little split in the hub axle wiring, but I looked and nothing is shorting. And it's been just like that for thousands of miles. I highly doubt it's that. The bike has been sitting. I have OVERHEATED THE MOTOR BEFORE. I got it REALLY REALLY HOT, burn your skin hot. So it might be that. I haven't tried to plug in different combinations of the phase wires. Not sure if that would help because these controllers don't require it I believe. They don't need to a wire to plug in to learn. It's the voilamart hub motor off ali express. It's a 9c clone.

Ok here is what I have done so far to trouble shoot.

1)shorted phase wires together without power. There is cogging in the wheel.
2) tested hall sensors. They all read correctly between 0 and 5v spinning backwards
3) tested with a known good controller. Still the same problem
4)tested with a model specific computer for error codes. An error code popped up.
5) check for loose connections. I jiggled everything. No dice.
6) Tested with a different throttle. Still problem
7) unplugged everything but throttle computer. Still having problems

This leads me to believe the motor has something going on inside it. I need to crack it open. This video looks like the best way to get it open. I will bang it on a 2x4.

I need to acess the wire side too, but I guess the wire side can just be unscrewed because it doesn't have magnetic force behind it. Like I said I got it really hot a few times. And then I let it sit.

Edit: I was able to switch rotation by unplugging hall sensor, and then switching the green and yellow phase wires. However, the motor still stalls sometimes, and sometimes it even switches back to reverse. Scary. Also the halls aren't working in reverse mode. I haven't tried to plug in the halls with the phase wires switched.

IS it possible that the yellow phase wire shorted on the axle? IT was touching it. There was a gouge in the wiring.
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It turns out, the controller was busted. IT still works but the wiring has to be switched around. Pretty sure I shorted something somewhere, these controllers are very susceptible to shorting out.

I had tested with another controller, but forgot the hall sensor was broken with that controller. That is why it was spitting out an error code. All my controllers now have busted hall sensors in the controllers. IT's awful.

It's kind of scary using a controller where it suddenly reverses direction. It doesn't feel like I am getting nearly as much power as I was before. IS it even safe to use controllers like these?
Well...? I got the motor running foward. The halls no longer work. I had to switch the phase wires G to Y. ITS RUNS in sensorless mode only. Can I damage the motor this way?
Can I damage the motor this way?
No. You already did that.

If it runs (relatively) smoothly and at the right speed, and delivers the expected amount of torque, then you have normal sensorless operation.
Having a spare sensorless controller is important, along with the fuses, 9v, a spare throttle or 2 and perhaps some halls, maybe a spare multi meter. I would buy the sensorless controller without any of the display crap.
Having a spare sensorless controller is important, along with the fuses, 9v, a spare throttle or 2 and perhaps some halls, maybe a spare multi meter. I would buy the sensorless controller without any of the display crap.
Can I get a link to that controller? My problem is I keep shorting out controllers. Its probably just because I shove the wires into a bag and dont cap them

Yeah I'm not riding that bike. Occasionally it sputters like it wants to switch directions.

I want a controller that can do 48v to 102v and can handle 40 amp
Well I road the bike a little bit. Sometimes I can feel the motor cog or get a little jerky at high speeds in sensorless mode. IT's kind of scary. It feels like the controller is trying to reverse itself.

Where is the instruction manual on troubleshooting motor noises on here? I can't find it anywhere. I stopped riding the bike for now.

To retiterate it's like the motor is "hesitating" but it does it at 28 mph occasionally.
What is FOC?
Field Oriented Control. Rather than arbitrarily approximating the motor's rotating field as a trapezoidal wave or a sine wave, it uses closed-loop feedback to juice the stator coils to match the rotor's permanent magnet field. It's the most power efficient type of control for brushless DC motors, and usually quietest. It requires an unusual amount of computational juju, so the controllers that do it are relatively expensive.