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My current ideas a bike gen motor:
Permanent Magnet (PM) DC motors make efficient slow speed DC generators. These are more efficient than Car alternators. Alternators waste some of the generated current to produce a magnetic field in the field coils. Alternators need a higher speed to be efficient than PM DC motors turned into generators. PM DC motors can be bought used for as little as $5 on up at electronics scrap yards. I am currently testing some surplus reel to reel 1/2" tape drive PM DC motors as generators that looks promising for this application.
As far as how to put it on the bike.
My current thought is to use a proper sized cylindrical pulley on the generator (for proper speed) hinged and spring loaded to hold down on top of the tire of the pedal driven tire-wheel. The drive wheel would be mounted just off the ground so that it can freely turn. If an exercycle then the hinged point can be the handle bars. If a bicycle the hinge point can be attached under the seat or to the support that holds the bicycle off the ground.

I don't think a regulator is needed. I doubt anyone is going to peddle fast enough and long enough to harm almost any battery one would use. I think it would be desirable to have a Voltmeter to tell when the battery is full and a Amp-meter to tell how fast it is charging (mostly a moral booster).

Offered by Mike.