Stereo experts only

[AnthonyF]

whatever amperage your alt charges it is what you want size fuse you want to use. I know I have a 230 amp alt, and I have a 250 amp fuse inline on the way back to the battery.

As david said, the fuse is to protect the car, not audio equipment. In this case you need to fuse both sides of the wire because you have a power source on both sides of the wire. Instead of a fuse you could use a circuit breaker. It does basicly the same thing, but they tend to be a bit smaller than a fuse and fuseholder would be.

i still dont understand why your saying i'd need one. Im going to having the exact same setup. only difference is my power will be connceted under the hood and brough towards the back....

[Turbo04]

i still dont understand why your saying i'd need one. Im going to having the exact same setup. only difference is my power will be connceted under the hood and brough towards the back....

If something happened and the wire was shorted between the alt and the battery you have the potential :

Best case: Alt and Battery both fried and shot. Need new ones.

Worst case: Alt and battery both fried...but it doesn't matter cause the car went up in flames.

Bet your ass that the worst case scenario is what you would be facing if the you did NOT fuse the wire and it shorted somewhere between the two. Stock I'm willing to bet your powerwire has whats called a fuseable link built into the stock wire. If that wire developed a short between the two then the wire basically burns itself into two seperate wires...thus breaking the circuit...that is why there is no need to have the alt wire fused seperatly. I'm willing to bet the kits you buy to move a battery to the trunk do not include a fuse with it because
A: they are more geared tword race car types and thus have some type of kill switch or switches added to the car.
B: Every car model has a different amperage rated charging system and trying to build a "one model" fits all battery kit just wouldn't be feasable. Thus you have to source your own fuses/breakers.

Either way do NOT ever run a battery to the trunk if it was not stock without fusing the power wires running back. When and if the car goes up in flames and your insurance company discovers the truth...they will not pay not to mention how dangerous it is to do it that way. You want a fuse on each side no more then 6-12 inches from each power source (alt and battery) that way if a short devloped you run less risk of overheating the wire leading to a fire.

thumbs up to BMW/mini for putting my battery in the trunk as well....