For me, I just went with my amp manufacturer’s recommended fuse size. I don’t know what amp you have, but it’s manual should give a recommended size.Great, but how can I know how much AMP do I need to put? I have 80 now, which is not enough because it blew up twice..
1800 rms at 1 ohm
Don't run a 250 amp fuse on 4 gauge...
Spend the money. Buy 1/0 OFC.
Don't risk your car burning the the ground over wire.