Im gonna be doing the big three upgrade on my xb and between the amp and battery + I'm going to put a fuse between them (recomended from several post i've read) and im confused on if the fuse i put in it is supposed to be the rating of the 4 AWG wiring (125 amps) or the rating from the alternator (80 amps?) ?

 

Anyone?

 

The fuse should be large enough to support the current draw of the devices connected to it, so in this case, at least the same value as your amp's fuse. The purpose of the fuse close to the battery is to prevent frying anything in the event of a short, so the 125 amp you asked about would be fine, it'll blow as intended if the positive hits ground.

 

The fuse should be rated at or less than the capacity of the wire its protecting.

That fuse is for a dead short condition. Fuse blows so the wire does not start a fire. The device fuse in each device will protect the amp/HU/etc.

Robert

 

Ok. perfect. Thanks so much!