WHY is the alt--->batt wire in the Big 3 fused based on wire size?

[iceteebone 5,000+ posts]

lets say you get into an accident a sever that wire, if it's fused it'll blow and you won't have a live wire that could start a fire.

 

[phenryiv1 10+ year member]

lets say you get into an accident a sever that wire, if it's fused it'll blow and you won't have a live wire that could start a fire.

I was not asking why it was fused- anyone can figure out the reason for that. I was asking why it was fused based on wire size and not based on alternator amperage.

 

[nebraskaz71 10+ year member]

ok i'm realy really new to this stuff but i'm doing a 220amp ho alternator and the big three using 0ga wire. What size fuse should I put inline..... I dont know what that size wire is rated at? thanks an advance and sorry this has probably been asked but I do not understand haha

 

[helotaxi 5,000+ posts]

250A should be fine.

 

[05AztecRed 10+ year member]

I was not asking why it was fused- anyone can figure out the reason for that. I was asking why it was fused based on wire size and not based on alternator amperage.

Becuase the wire size is based on how many amps "flow" thru it. A 1/0 wire can have 300 amps of power flow through it before it loses integrity(if you will) and starts to fail. Since you don't want the wire to fail, you fuse it at the maximum amount of amps it can handle, hence a 300A fuse.

Every other wire out there has a maximum amp number that it can handle, and you would fuse those wires according to the max amps...

 

[Thnking 10+ year member]

Becuase the wire size is based on how many amps "flow" thru it. A 1/0 wire can have 300 amps of power flow through it before it loses integrity(if you will) and starts to fail. Since you don't want the wire to fail, you fuse it at the maximum amount of amps it can handle, hence a 300A fuse.
Every other wire out there has a maximum amp number that it can handle, and you would fuse those wires according to the max amps...

If you read my post I mention why this is wrong.

Wire size is picked on current through the wire. Fuse size needs to be selected based on the same. The current through a wire should never nominally reach teh wire's insulation current threshold.