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knightscape is offline
Jan7-10, 04:02 PM
P: 3

Limiting alternator output with resistors in parallel

A fairly common number tossed around by cyclists is 150w for sustained output. I'm a fairly strong rider so I anticipate that I should be able to get that much out of my legs. I know there's drivetrain loss in the system and other limiting factors. I'm basically looking to see how much of that I can capture and still get a good workout. So a key for me is reigning in the demand from the alternator. One of my basic requirements is that I can ride it for an hour.

I tried putting these same resistors in series on the field line but it didn't seem to affect the level at all, which led me to the question, "How do I figure out what level of resistance will get it under control?" Placing them in parallel on the alternator's output line does bring it under control, just a little too much. I'd love to zero in on the best solution without throwing money at resistors and guessing. Whether that solution is placing them in series on the field line or in parallel on the output line doesn't so much matter to me, but I'm at a loss as to figure out how to come up with a theoretical level of resistance to try on either.

I can measure that the field charging line draws about 3A when powered up. The output line with no resistors inline will put out something >5A and < 15A with me grinding as hard as I can against it for a few minutes.