motor cutting out over bumps

[headwind]

Hi,
My Bafang hub motor has started cutting out for an instant over even the smallest bumps (such as the joint between concrete pavers). It then cuts back in immediately, sending a jolt through the bike. Has anyone else had this problem? Or can suggest a likely cause?

Thanks.

 

[dogman dan]

That's definitely going to be a problem in the wiring, one plug or another loose, cut wire, or a broken wire hidden under the insulation. something like that.

 

[ecycler]

^This. I would start with your throttle and its wires as the most likely culprit. Generally when a phase or hall wire is that loose you are going to see other symptoms as well or the controller will shut down until repowered.

 

[headwind]

Cool, I'll check over the wiring carefully.

Thanks for the replies.

 

[cycleops612]

Obvious, but JIC, diagnosis can be simplified by simulating bumps in the work shop. Suspended right from a rafter, you can slam the non drive wheel against the ground while running the bike stationary.

 

[headwind]

Obvious, but JIC, diagnosis can be simplified by simulating bumps in the work shop.

Thanks. I wish I had a proper workshop! :? Instead, I had to rig up something dodgy in my living room, taking care not to scorch the carpet when dropping the spinning wheel onto the floor

Anyway, despite sounding and feeling like a mechanical problem, I think you guys were correct about the wiring. The plastic casing on a bullet connector had come loose, so I think this was shorting out. Since fixing this I've been pounding over bumps without a problem, touch wood!!

 

[Eskimo]

I had this exactly same thing with my DD motor for months. I tried to figure out what it was and finally today found out.
My PAS wire from the crank was shorting on bumbs. I re-wired it today and problem is gone.

 

[headwind]

Yeah it's a tricky one to chase down. Congrats on getting it sorted.