How much torque or horespower does an alternator use?

Question

how much torque or horespower does an alternator use? ballpark figures. and yes under heavy load. I would like to know on big alternators like 100, 150, 200, and higer. I need to pull atleast 400 amps continuosly maybe more. How many alternators would I need and batteries? How much horsepower would I need to keep all the alternators spinning and be able to drive normal?

Answer 1

About 1hp for every 12 amps.  A 600cc motorcycle engine with 45hp could easily deliver the 400 amps you're looking for.  GE makes a 185 amp marine alternator that is very fluid.  I'd recommend three of those.

A lot of it has to do with the way you have the cams and belts laid out.  A 5hp lawn mower engine could potentially turn a normal 100 amp at approximately 65-70% at probably a rate of about 1 gallon of gasoline per hour, but that 600cc engine with 45 hp could probably only use 1.25-1.5 gallons per hour.

Therefore, if you're using electrolysis (1929 water car) or straight electrical power to build a hybrid for fuel economy, you might actually get better gas mileage with a higher horse power gas engine because it will idle lower.  If the 400 amps will move your vehicle 70mph, at 1.5 gallons per hour, that's about 45-50mpg, better than with the 5hp lawn mower engine for sure.