The battery is already has a 300A fuse, the charger will be literally 12" away.
Taking in to account the very small distance is it necessary to fit an additional 60 fuse/breaker.
asked
Fusing a Orion-TR Smart 12/12-18A Isolated DC-DC Charger
Input or output?
But on the input side there should be a fuse as close to the battery as possible 300A fuse won't give any protection to the Orion wiring.
On the output side, same applies. You should have wire large enough to handle the max output comfortably, so a fuse provides no protection at the Orion end, but at the battery you do need something, 300A fuse won't protect the wiring.
I'd be inclined to include a fuse sized to protect the wiring and also limit fault currents into/out of the Orion. A 30 amp fuse would be more than sufficient. Maybe an in-line fuse could BE the connection between the battery and Orion.
The fuse (or circuit breaker) would provide a way to power down the Orion for maintenance without risking shorting the wire to the battery when making connections.
