If you think the generator might produce 8A, then the charge controller should be this much, plus a safety margin. 8A would charge a 28AH battery in around 3 hours.
24V, 8A is about 1/3 horsepower. Your charge controller would need to be designed to manage the burden (demanding less power). Some athletes can generate that much power, but you can ask them not to.

If your "bicycle" rider is achieving a virtual 10mph, that's around 50 to 100 rpm. A "1800rpm" generator would need to have some gearing (some of this can be done in electronics). Beware of losses in gears and chains.

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de KI6RWX

 

Thanks alot =D

 

Does anyone have a schemetic of a charge controller which does not use PV but a voltage regulator ... i m not really sure how it goes, but definelty not using charge contoller with a solar source