12v power source.

[stardevlp]

Try this 26" 21 speed bike, brace the back tire 1 or 2" off the ground, remove the tire & replace it with a auto belt length of 78" or longer & an auto alternator. Connect the wire to the alt to a 12v auto batt, (http://alternatorparts.com/understanding_alternators.htm) Spin the bike tire @ (www.BikeCalc.com) Chainring 38, Cog 38, or 19 MPH, rpm's at the alt will be about 3300. You are now charging the 12 v Batt.

[USMC0331]

Or get a solar panel.  The amount of energy expended to produce the energy saved is not worth it.  It also keeps you stuck in one position for hours to charge a battery.

[APX808]

I had read that car alternators aren't very good because they are made to work at high RPM, giving them 3300 will make them work fine?
I rather having the solar panel, but this sounds like a nice backup for cloudy winter days.

[JohnyMac]

Good post Stardevlp! Welcome to the forum.

IMO, the best alternators to use in a low RPM situation is a marine, high out-put alternator. A great company to check out is Balmar. http://www.balmar.net/

[new age patriot]

most vehicles at operating speed only run about 1500 rpm so 3000 would be plenty.
but i also agree that would be a last resort because of the time required.
And if you used a large enough alternator you could possibly run a power inverter to get some 110V

[APX808]

@new age patriot, most vehicles run about 3000 RPM but using belts and pulleys make the alternator turn faster.

[Reaver]

Regardless of how much you get for what you put out it's still good knowledge to have. Thanks NG

[gapatriot]

Gm single wire alternators make power at 1500 rpm and they are cheap. Gear ratio coming into play a bike wheel to an alternator pulley will take you to well above 1500 with very little work.