I have experimented with several types of auto alternators and generator (old VW) and have found that there is a large variance in amperage produced by different makes. Forget car alternators and find one in a schoolbus or similar vehicle that reguires an industrial battery, like tractor trailers, heavy equipment etc. The one I use came from a 1985 bus and produces 160 amps at the same general rpms as most 30 amp car alternators. Do you see the advantage here? Lots more power at same speeds, gear ratios etc., plus most can endure rougher treatment because they are built to take more vibration, etc.
Offered by Woodie.
The greater the amount of current drawn from a generator, the more energy required to turn the generator shaft. Whether using pedal-power, wind, or water, the more load (current) placed upon the generator, the slower the pedal or blade will turn with a fixed wind speed, water speed, or effort on the pedals. Therefore, it does no good to put a 100 amp generator into service over a 60 amp generator if the power source is only capable of producing 480 watts (12 X 40). This should be of primary importance in designing a pedal driven system. A wind driven system can be slowed to a halt if it has a large generator and is charging enough batteries at the same time. You can actually regulate maximum blade speed by adding and removing batteries from the parallel connected battery bank.
Offered by Ron.