- Joined Oct 29, 2013
I'm using a capacitor to smooth power on a motorcycle without a battery, and I'm going to add a fuse to protect the bike (prevent a fire) in case something happens shorting the capacitor or the user connects it backwards. So I'm trying to calculate the smallest fuse I can get away with. If I ignore the initial charge (it's too quick to pop the fuse) I believe all I need to calculate is the current due to the ripple voltage. Lets just use idle speed for now. The screen shot below shows start-up and idle. It's a 10,000uF cap, and the worst case ripple appears to be about 5v at about 100Hz. I don't know the ESR, so lets assume an ideal cap to get the worst possible case current. Q = CV . So worst case change in charge would be 5v * .01F = 0.05 columb per cycle. 0.05 columb/cycle * 100 cycles/sec gives me 5 columb/sec, or 5A. ... OK how badly did I butch this?