Find the install wiring diagram for your inverter.
it is the Magnum ME-DCLD, DC Load Disconnect Pigtail Adapter.
The ME-DCLD (DC Load Disconnect) pigtail adapter is designed to provide a means to DISABLE the inverter function when a 12 volt DC signal is removed. This is useful in applications when a vehicle or boat is placed into storage and the battery disconnect switch is turned off to disconnect all DC loads, the inverter can also be automatically turned off if the ME-DCLD is installed.
You also need to know where the other end is connected.
Most RV batteries live a long and useful life, some are murdered.
2000 National Sea Breeze F53
1998 CRV Toad