In previous years we'd keep the trailer at home between trips, plugged into the 30 amp power supply. This year we're trying something new - using the storage lot for longer gaps between trips. Because we don't want parasitic draw to exhaust the battery, I installed a battery switch - Princess Auto SKU 8105033.
Before installing the battery I wired the switch. The black wire connects to the negative battery terminal and the trailer ground wire connects to the other switch terminal.
Because there's limited space inside the battery box, I clamped the switch (gently) in the vise and cut the terminals short.
I traced a rough outline of the switch back on the outside of the box and marked where I would drill the holes.
A bit of filing and the switch was in.
I made a plate to go between the switch and the battery; this will keep the terminals from gouging the battery case.
The plate in place.
We have power to the battery.
The key stays in the battery when the switch is on. When it's off the key will hang in the (locked) trailer.
Since we've switched to a solar battery box, the old box (switch included) is no longer in use.