We often idle our V10 for awhile before using a small generator plus our 13.8 volt stock converter to charge our AGM batteries. Our little generator is very, very quiet and runs 4-5 hours on 1/2 gallon of gasoline when charging our AGM batteries through the converter.
I agree with MEXICOWANDERER: Switch to an AGM battery. I recommend a Fullriver Group 31 AGM battery - their model DC115-12. Fullriver even recommends that their AGM battery be maintained when not in service using about 13.6 volts, so your stock converter can even maintain it while your RV is parked in storage. Note that an AGM battery can both be maintained and charged from the same low proper voltage because their chemistry makes them accept current better at all voltages.
