Hi,
My two banks "meet" at the inverter. The OEM bank powers the 12 volt side of the RV.
I chose the Magnum 3000 watt hybrid--so I can now charge either bank at up to 125 amps. I left the OEM 40 amp converter in place and tend to use it when I have 30 amp shore power.
I use the Magnum when I have 15 amp shore power as it is possible to "dial" the input to 15 amps--which means I don't blow a breaker--but the hybrid lets me run the RV as though it were on 30 amps.
I also use the Magnum if I plan on generator recharging--though so far that has happened exactly once. (solar is a gooooooood thing!)
I also have switches so I can charge either bank from solar, and either bank from the alternator.
Definitely reinforce the storage area for the new bank. I'd also consider having a 12 volt in the OEM location. It is rare for an RV to have too much storage.
