Help! Loud vibrating rear hub motor after putting it under load while stationary.

ZeroTPA

Just Joined
Jul 5, 2023
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Hello all, this is my first post on this forum, I'm excited to join this friendly and welcoming community!
A friend of mine sold me an eBike with the a 36v Voilamart 500W rear (Brushless Gearless) motor. It is around 3 years old and had been running fine with me over the last few days of having bought it. I have it installed with a simple throttle. (It might be important to know that he, being quite a light chap, was riding it for 3 years, and I am a tall and heavy guy (140kg), and have been riding it without issue for a few days until now).

Then this morning my curiosity got the better of me. I wanted to see what would happen if I throttled the motor while holding the bike stationary. (I know this was stupid, and I honestly don't know what I was thinking). The bike jerked forward a little, and then stopped moving, like the power to the wheel had cut out. I assumed this was just some sort of safety feature.

When I went to set off however, the wheel motor began to make huge amounts of vibrations (vibrations which can both be heard and felt very strongly), and here are some symptoms:
  • The wheel still spins freely when I cycle under pedal power, but the moment I send any power to the motor, it begins to vibrate.
  • The motor also no longer has any torque, it cannot get the bike moving except for if I lift the wheel off the ground, the motor can spin the wheel, but any resistance causes it to cut out.
  • I tried pedalling and building up some speed myself (maybe 10mph), and then switching on the power to the rear motor and pushing the throttle. Interestingly it starts vibrating instantly, even when I stop pushing down on the throttle. The only thing which will get it to stop is to flick the switch to cut the power to the motor.
  • Sometimes when the wheel is lifted off the ground, the wheel will move in a jerky fashion, once or twice, and I have seen it even jerk backwards a few times (again with hardly any torque).
  • Thanks for the advice. I found that if I unplug one of the connections from the controller, the wheel runs in reverse. The vibrations and noises do not happen if the wheel is powered in reverse. Is this consistent with MOFSET failure?
I wonder if someone could help me understand how badly I've busted this thing, and what steps I can take!

(Here is a link to a video if anyone is interested
)

Edit: I fixed it. I learned that the Hall sensors were bad by probing the cables with a multimeter. I will replace the hall sensors but my temporary fix is to run the motor without a hall sensor by unplugging the hall sensor cable, and by reversing the phase cables so that the wheel spins in the correct direction. It's a bit louder than it was before, but it runs like it did before!
 
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