Have you ever started packing your RV trailer for a camping trip only to find the batteries completely dead? You can easily prevent this from happening next time by installing a battery disconnect switch in your travel trailer. When turned off, the disconnect switch prevents any electricity from leaving the battery. But you can easily turn it on from inside the RV, without having to mess with battery cables or terminals. It's also a handy location to turn off the battery power when you need to work on your trailer's electrical system.
Disconnect the trailer battery cables.
Find a cabinet near the battery compartment in which to install the switch. There should be enough room in the cabinet to run two wires from the switch to the battery compartment.
Use screws to mount the battery disconnect switch inside the cabinet surface. Be sure to keep the screws from coming through the cabinet wall; you want to keep the outside of the cabinet looking nice.
Mount a power post connector in the battery compartment near the original load cable, the cable originally connected to the battery positive terminal. The power post is an insulated 3/8-inch bolt with nut and washer to mount cables on.
Mount a Mega fuse holder, with a 100 amp Mega fuse, in the battery compartment near the positive battery post.
Cut a 4-gauge wire with the cable cutters, long enough to reach between the battery switch and the power post connector in the battery compartment.
Cut a length of 4-gauge wire long enough to reach between the battery disconnect switch and the Mega fuse block, in the battery compartment.
Cut a 4-gauge wire long enough to reach between the Mega fuse block and the battery positive post.
Use a pocket knife to strip 1/2-inch of insulation from the end of each of the three cables.
Use the cable crimpers to crimp 4-gauge cable lugs to the ends of the disconnect switch to power post cable; both ends take a 3/8-inch ring cable lug.
Crimp 4-gauge cable lugs on the disconnect switch to Mega fuse-holder cable.
Crimp 4-gauge cable lugs on the Mega fuse holder to positive battery terminal cable. The fuse end takes a 5/16-inch ring cable lug. The battery terminal end takes a top post positive battery cable end.
Crimp a 3/8-inch ring cable lug to the end of the original load cable, the one that used to go to the positive battery terminal.
Make sure your new RV trailer battery disconnect switch is in the off position.
Bolt all the cable lugs to their designated locations. Connect the original load cable to the power post connector, the cable from the power post connector to the battery switch, the cable from the battery switch to the Mega fuse holder and the cable from the Mega fuse holder to the positive "+" terminal of the battery.
Turn the battery disconnect switch to the "On" position and ensure your DC appliances are working.
The 4-gauge wire should be red in colour.
Do not connect power to the circuit until all the connections are bolted in place. Connect the fuse-to-battery wire last.