24v or 36v minimotor.. 250w what exactly does the watt parameter mean?

[Sangesf]

Also, if I'm using a 24v minimotor and I'm using 15a continuous, does that mean I'm going to ruin the motor because I'm using 360w continuous?
What about my 36v minimotor if i'm running it at 10a continuous, will I ruin it too?

What's the deal?

(prolly a newb question, but what can I say?)

P.S. If I'm running a 24v minimotor on 36v and run it 10a continuous for 360w total will that ruin it too or faster then if it was a 36v one?

[Bikemad]

Frank, a 250W rating normally relates to the safe continuous power output of the motor.

If it has an efficiency of 80%, it would need to consume around 313 Watts of power in order to produce an output of 250 Watts.

So your 360 Watts of consumed power is actually producing around 288 Watts of output. (Only 15% more than it's rated output)

As long as the motor does not get too hot, you should not have a problem.
It's the excessive build up of heat that tends to cause motor failure by melting the insulation on the wires, resulting in a short circuit.
From what I've seen, the insulation on the hall sensor wires seems to fail at a lower temperature than the lacquer on the windings themselves, causing failure of the hall sensors.

Running a 24V motor on 36V
At full throttle, I would expect a 24V motor to run 50% faster than a 36V motor using the same 36V supply.
The 36V motor should draw less current and therefore generate less heat because it is actually doing less work!

So under maximum load, the 24V motor would probably fail before the 36V motor as it will be drawing 50% more current and working 50% harder, but if both motors are run at 36V, and limited to the same 10A current, I don't suppose there would be much difference between them.

Alan
 

[Sangesf]

Thanks Alan that clears up quite a bit. 

I've run both of my two 24v motors on 36v and 10a continuous for approx 2 hours in 85 degree weather and the motors were only luke warm, which I would guess is not "hot", so basically I should be ok, right?

[Bikemad]

I would have thought you should be fine if they are not hot, but check for heat where the axle exits the hub on the wire side, as the axle may get warmer here due to direct conduction of the heat through the stator.

Alan
 

[Leslie]

Expect the speed and torque at 36v to go up at the expense of efficiency.  36v is within GM spec though.  I would guess these hubs are not designed to cart trailers and taking heavier loads.

One idea I had was a dual mini motor at 36v on a very light racing bike using a light 16ah lithium pack.  This would hand back efficiency at 36v and you have 500watts powering a bike that has less impact on a single pack.