Ok an inverter charger has TWO 120 volt lines going to it. In and out. That said some RV inverter only have automatic pass through but usually those are smaller and thus have IN and OUT lines. Your device model number will tell me and the owner's manual for the device shold tell you.
I would recommend a Progressive Dynamics 9200P the last two digits are determined by your battery size... (I will explain the P) Figure the C-20 battery capacity
Group 24 75
Gropu 27/29 just under/over 100
Group 31 130
Group 4D or a pair of GC-2 220
Multipley by 0.3
Get as close as you can to that. So 2 pair of GC-2 9280 (Biggest they make)
One pair 9260
These units have a 20 amp plug so you will need to make an adapt-a-cable or if there is a power in lead taped off at the converter just install a 20 amp 15/20 amp outlet (They have a "T" shaped neutral)
I've not found a better converter
Make an adapter cord in any case.. I've been on 20 amp sites and I plugged in my PD9180+wizard and used the inverter to power the house 120 volt stuff
Oh I said I'd explain the P.. P-lug in