How long to burn out a hub motor at maximum current?

[RollingChunder]

I am considering using "walk assist" up very steep inclines at 6km/h while carrying a lot of weight. High load at low speeds creates heat in a motor. So considering worst case scenario, how long can a motor last at max current while stationary i.e. with the brakes applied? Is it under a second and it will pop? Or do you need to give abuse for at least 30 seconds before it gives up?

Also are there warning signs such as the casing getting extremely hot first?

I know it will depend on the amps being applied but consider an average ebike hub kit.

 

[Saracen]

How long is a piece of string ?

You ask, with a lot of weight, Errr !!!

Why is it not carrying you using pedal assist and riding up ? why do you need walk assist ?

 

[saneagle]

I am considering using "walk assist" up very steep inclines at 6km/h while carrying a lot of weight. High load at low speeds creates heat in a motor. So considering worst case scenario, how long can a motor last at max current while stationary i.e. with the brakes applied? Is it under a second and it will pop? Or do you need to give abuse for at least 30 seconds before it gives up?

Also are there warning signs such as the casing getting extremely hot first?

I know it will depend on the amps being applied but consider an average ebike hub kit.

There's a fair chance that the controller would pop first.

I doubt that walk assist has enough power to move a heavy load up a steep hill unless you have a Bafang BBS** specially programmed for it.

 

[RollingChunder]

There's a fair chance that the controller would pop first.

That's helpful to know thank you. It had enough power with just me on it but I wonder how much damage I'm doing to it or if there is room to add luggage.

Also it is out of curiosity I asked about the stationary motor under load. I'm not flush enough to try it myself. How long until the controller popped then?

 

[AntonyC]

My controllers have stall cut-out but I don't know if that's usual, without it MOSFETs could last seconds.

A hub motor shell is well separated from the windings, so the windings can smoke and smell while the casing's still warming up. For an EAPC system 30 seconds and up is probably the better guess.

Grin's motor simulator tracks core temperature and overheating, if not for your motor then choose a similar one. It helps you choose between pedalling in low gear with modest assist or using max assist to get the hill done in the shortest time possible. Here's their tutorial about temperatures.

 

[saneagle]

That's helpful to know thank you. It had enough power with just me on it but I wonder how much damage I'm doing to it or if there is room to add luggage.

Also it is out of curiosity I asked about the stationary motor under load. I'm not flush enough to try it myself. How long until the controller popped then?

You should never run a motor under power at low speed unless it's a low speed motor. You can get any one of these three faults, each of which can then cause you to get the other two: phase wires melt; MOSFETs pop; motor coils burn. The only way you know it's happened is when the motor stops, then it's too late.

Generally, keep any hub-motor above 8 mph and you should be OK.

If you're lucky, your controller might have a temperature sensor in it that switches off when it gets too hot, but I wouldn't count on that.