How efficient are DC motors as generators ?

[macelyne]

I have a general question concerning electric motors.

Actually I'm looking for a small generator,
but my webresearch had no result.
It seems that generators are not built in little dimensions.
The smallest I could find, was a 3 Kilo generator, 1500 rpm, 582 watt.

Does anybody know where to find something with about 50-100 watt output ?

The other approach to my experiment would be to use normal model motors,
but I know that their efficiency as generators is not very well.

But how much does the given efficiency of a DC motor decrease when it is used
as a generator ?

I couldn't find a single vendor that was able to give me an answer.

Even manufacturers don't give any hint when writing about the capabilities of their products.

[Roen Hayden]

This idea may or may not help you but it you wanted to get 2 Dc motors hook one up to a battery and attach it to the DC motor and hook a multimeter to the wires of the other DC motor.  I dont know if this would make sense to anyone else if it does not just ask.

[Doug1]

Wheel chair motors. Luck would have it most of them come with two and a nifty controller and gear boxes.The built in chargers are crap, only good for spare parts after you strip down the charger. Nice motors though and they will work on 12 volt even if they are 24 volt. Imagine how well built they have to be to haul some larger then life person around all day.