You have a 7355 power centre with its converter as the lower portion. Drop the top lid and see the circuit breakers and DC fuse panel. You don't need to get at the converter below with the four funny screws holding the cover on.
When plugged in the converter puts out 13.8v DC and that is above full battery voltage of 12.75, so the monitor on the range hood will say the battery is full even if it is dead or not even there.
Check the monitor when not plugged in and your portable charger not on or any solar charging on to get a better reading of the battery's state.
A portable charger on the battery out front will sometimes not work right if the converter is on doing its 13.8v. Try unplugging shore power to kill the converter first then try the portable charger. Once it is going plug back in so the Rv has power again, and the portable charger should keep running.
Instead of using the shore power you could just turn off the converter with the circuit breaker, which shares with the 120v receptacles and the 120v lights. Beware of wrong labels on the circuit breakers. Good idea to confirm each breaker one at a time for what it goes with.
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.