How different is an electric motor from an electric generator

[dotancohen]

I recently bought a hand-crank phone charger. When I opened it up, it looks like the generator is simply a repurposed electric motor. I have not yet tried to flow current through it to see it if would spin. However, I wonder how similar a motor is to a generator. I have heard of electric cars with regenerative brakes with a single component performing both the motive and stopping power. That leads me to these curiosities:
Are there tradeoffs in making a device either a motor or a generator?
Are they exactly the same?
If I am holding one in my hand can I tell if it was engineered to be used as a motor or as a generator?
Can I replace the small generator in my hand-held battery charger with a larger motor from a dremel tool and produce more power?

Thanks!

 

[I_am_learning]

I recently bought a hand-crank phone charger. When I opened it up, it looks like the generator is simply a repurposed electric motor. I have not yet tried to flow current through it to see it if would spin. However, I wonder how similar a motor is to a generator. I have heard of electric cars with regenerative brakes with a single component performing both the motive and stopping power. That leads me to these curiosities:
Are there tradeoffs in making a device either a motor or a generator?
Are they exactly the same?
If I am holding one in my hand can I tell if it was engineered to be used as a motor or as a generator?
Can I replace the small generator in my hand-held battery charger with a larger motor from a dremel tool and produce more power?

Thanks!

No, you shouldn't replace the small generator with larger generator (motor) without changing rest of the charging circuitry. Moreover, your battery has a maximum limit on how fast it can charge, no matter how much power you got, you can't charge it in minutes.

Most DC and AC, Generators and Motors are constructionally similar, however I am not aware if there is some extra-engineering to tailor it beneficial for generating/motoring.

I am aware of at-least one motor that can't be used as generator, its variable-reluctance-stepper-motor.
I am not aware of the reverse.

 

[dotancohen]

Thanks for the insight. I had cranked the handle for over an hour (long drive) and gotten no real additional charge into the phone. The device is a cheap Chinese crank:
http://cgi.ebay.com/Dynamo-Hand-Crank-USB-Cell-Phone-Emergency-Charger-NEW-/300540938129?pt=PDA_Accessories&hash=item45f9a2c791

The page specifies to spin it at 100-120 RPM, not an easy feat! I probably spin it at half that speed.