We are often asked about fusing cables and accessories.
1) Make sure the cable is rated to the load. (Check the documentation supplied with the accessory)
2) Use the 7-40-72 Rule for fitting your fuses or breakers. The American Boat & Yacht Council (ABYC) has set up these guidelines for safe operation of DC circuits.
Fuses or breakers are required within 18cm (7") of the battery switch on wires leading to various loads, the 18cm (7") dimension can be extended to 101cm (40") if wires are enclosed in a sheath or conduit in addition to the wire primary insulation, and within 183cm (72") on wires leading to loads directly from a battery.