Originally Posted by Brooksie
The fuse should be sized to protect the wire or the consuming device whichever is less.
The consumer should be protected by the branch circuit breaker or its own fuse.
The wire serving the branch should be fused as close to the source (switchboard) as possible.
Fusing a circuit at the consumer (as in fusing the alternator output at the battery) does nothing to protect the wire. If that wire shorted to some part of the engine "upstream" of the battery, the wire would burn.
The only fuse you should put on the battery is something like the MRBF type sized to protect the wire between the battery and the switchboard. Do not fuse the starter. Install a battery switch or continuous duty relay if you are concerned about a hung starter or wish to have start isolation.