Megafuse size

[huzilulu]

Hi

I am considering a megafuse next to the battery, and run all the electrical connections off the fuse - the Ultima loom, LS engine loom, extra AB power loom. The only connection on the battery will be the Megafuse, and the battery cable to the starter (which I will NOT put on the megafuse)...

Given this setup, what is a recommended fuse size? 100A? 125? 200? The fuses go up to 450A. Also, most of these fuses are 32V - will that be a problem for our 12V system, or does a 32V fuse also protect a 12V system?

Thanks