Fermi estimation flubs… guessed the amperage of a car starter motor wildly wrong this morning
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In my defense I was being more lazy than stupid… upon learning that USB-C can do 12V and fairly high current, I wondered if it could jump start a car (answer, no… off by 2 orders of magnitude… 5A vs ~200A)
But embarrassing even as a lazy guess
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I have bad intuitions for rated current vs conductor dia, but not this bad. Here’s a handy chart. ~200-300A calls for a conductor about 0.4” — about a finger width.
What’s “chassis wiring” btw?? Why is it max chassis amps so much higher than transmission amps at smaller sizes
Replying to
Apparently because they’re routed seperately and not in a bundle, so they are cooled much better. In a tight bundle they all dump heat into each other and don’t have much surface area for dissipation, so heat+resistance goes up faster, hits levels that melt insulation earlier.
Replying to
AFAIK the amps rating is for a certain wire temperature rise, which would depend on the type of installation.
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