Torque Numbers for E Bike Motors

[Hoggdoc]

This is something that I have been trying to find an answer for. How can a 250W motor have the same or near the same amount of torque a 750-1000W does. As I see it the amount of amps it takes to generate 250W @ 48V is vastly different than that of 750W @ 48V and have a effect on the torque output.

Can someone explain this to me or is it just marketing?

 

[bpratl]

Good question.

 

[Hoggdoc]

Good to know I'm not the only one that wonders about this. Some must have the real answer hopefully they will chime in soon.

 

[Scona]

I have always assumed that the 250 watts is the European restriction on some e bikes.
So motor manufacturers are not free to advertise 750 watts as they do here. Perhaps
their work around is to advertise large torque numbers that do not coincide with the
advertised wattage but are coincident with the motors actual performance.

 

[Hoggdoc]

I have always assumed that the 250 watts is the European restriction on some e bikes.
So motor manufacturers are not free to advertise 750 watts as they do here. Perhaps
their work around is to advertise large torque numbers that do not coincide with the
advertised wattage but are coincident with the motors actual performance.

That's my feeling as well, otherwise the advertised torque numbers for these low wattage motors makes no sense.

 

[Yogaduke]

There are two ways to rate an electric motor. 1. Controler amps times battery wattage. 2 a contentious use rating. Ebikes coming from China use that becaue they can set what rating they like. They can say it is a 750w CU and that means it can run for the life of the motor at 750w and at 751 it will over heat. If it was made in the US or Germany they use amps times wattage. China says my ebike is a 750 watt ebike. But it would be called a 1440w ebike if it was made it the US or Germany. My what they say is 750w can put out 160nm of power.

 

[Funky]

All depends on where you are measuring the torque. If measured at the armature shaft the torque would be low, if measured at the driven wheel in it's lowest gear the torque would be at its highest, basically the gearing is a torque multiplier. Also cheaper motors will use more electric current to produce the same power. Which also means very expensive motors with tighter tolerances will give more power for the same current.