Welcome to the forum Charlie,
Before we can answer this question we need to know a little more about the converter (battery charger) in your motorhome. Your converter must be able to charge at 14.4V or possibly more to quick charge your battery. Tell us the brand on your converter and we can help advise you on that.
In addition, how long do you intend to be parked at any particular spot? What do you intend to run off of the battery(ies), and for how long between charges?
I suspect that one 12V battery won't get you far. I have 2 golf cart 6V batteries. I can watch TV all evening and run my furnace all night with 2 hours generator time in the morning and 2 hours in the evening to recharge the batteries for another night.
More information will get better answers. You might add a signature to your profile with more information on your RV. What chassis? What engine? What transmission? Do you tow anything? Etc.
2003 34' Georgetown on W20 Workhorse Chassis.
1998 Jeep Cherokee for a toad
UltraRV power mods to engine and transmission