Jerky Starts

Aloha, When starting out, the motor hesitates and goes into reverse for a split second and then forward causing a clunk. (If I slightly roll forward it is fine.
I checked all my wiring and also did a "re-learn" but still happens.

Probably totally unrelated, the motor is totally silent when driving and the only time I may hear a slight "rrrrrrr" is during acceleration, otherwise silence.

What is going on?

Normal operation for a brushless motor with no hall sensors. If you have hall sensors, they are not working and your controller has been working in sensorless mode. Some do that. It could be as simple as a broken contact at a plug to the halls. You might need to replace sensors in the motor. you can test that with an affordable motor controller tester from ebay.

If you are stuck with it, have a sensorless motor, then just get used to making that tiny roll forward each start.

So is the only function of the halls are for smooth starts?

francis

The halls time the pulses to the motor all the time. With sensor less, its possible for the motor to lose synch and start stuttering, but that is rare. But sensored will usually run a bit smoother at all times.

One extra thing about motor Hall Sensor use is that they’re often required for high RPM motors which require fast electrical commutations. Those type motors do not usually work well, if at all, on sensorless controllers.

Q100/128H geared hub motors being one of those motors. I would also guess the Bafang BBSXX series would have problems running on sensorless controller.

Ykick said:

One extra thing about motor Hall Sensor use is that they’re often required for high RPM motors which require fast electrical commutations. Those type motors do not usually work well, if at all, on sensorless controllers.

Q100/128H geared hub motors being one of those motors. I would also guess the Bafang BBSXX series would have problems running on sensorless controller.

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I am running my motor at up to 900RPM. Would that mean that the halls are working properly? (ie 38mph, 14.3" dia tire)

francis