I think what you are saying is your replacing the factory “converter” with an inverter/charger
or do you already have an inverter/charger your replacing?
the 2ga wire sounds like it powers the rv and has shut off switches. And supplies charge current to the batteries
3000 watts of 12v dc current is about 250 amps and will need much larger wire size like the 4/0 specified. But the 2ga wire can still be used as intended as long as it’s the proper size specified
there should be included wiring diagrams for the system that will specified wire sizes and connections
2010 Ram 3500 HD traded in for new 2015 3500 HD DRW mega cab with the 3.42 gears
I haven't hooked up yet, we'll see how it pulls with 17" wheels. (Pulls great !)
2014 Cyclone 3100
G614 Goodyears
Good Sam gps
Trimark keyed alike
Xantex 2000 watt inverter "Inverter Service Center"
Blue Sea System toggle source selector
L.E.D. running lights
Quadra Bigfoot levelers
Dexter wet bolts
Boyo wireless backup camera
EMS-HW50C
TST 507RV
Smittybuilt air compressor
Splendide 2100XC
26k Husky hitch
Mor Ryde pin box
6-volt 240 AH batteries
Added dinette
Replaced L.E.D. tail lights with Leading Edge Trailer light bars (made in the US)