Do hub motors have any overload protection?

[Charliefox]

A neighbour of mine electrified a hardtail MTB with a Bafang 350watt rear hub.Did a really neat job too. I asked him the other day how it went on a test run. " I was going to see you about that" he said. !The motor died on me" On probing for details it turned out he had got stuck in the wrong gears on a steep section( he hadn't cycled for years) and the motor got slower and slower. It was sucking in 460 Watts or so. I think it recovered later....hopefully!
I pointed out that electric hubs don't like to labour at slow speeds in the wrong gear. Guess he will have to up his cadence numbers and do a bit more work! I still wonder if his new hub motor and electronics came away unharmed?

 

[vfr400]

If it's still working, no harm has been done. The risk is more to the controller and wiring.

When you go slow, the controller gives the maximum current, but at higher speed the current is reduced by the motor. The faster you go, the less current you get, so the safer it is for the motor.

If you run the controller at maximum current for too long, it will overheat. If you're lucky, it'll have a thermal cut-out, which will prevent anything from burning, but at very low speed, the current is less smooth and that brings the risk of blowing a MOSFET in the controller. That in turn can burn out your motor if you don't stop trying to give power to the motor.

Some of the cheaper controllers have cheap wire and connectors for the motor. I've seen quite a few where the wires and/ or connectors melted when run at low speed for too long.

It's always best not to let the motor labour for too long when climbing hills, so it needs all the help it can get from pedalling, which, obviously, will be best when you're in the right great.