My motorhome barely charges the house battery when driving. When I need a good charge it's much quicker to run the generator and converter/charger than to rely on the engine charging it up (so I'll often run the generator while driving from one place to the next to get the battery recharged quickly).
propane is sometimes avaliable at gas stations, but I find the "techs" at gas stations don't have a clue. I have a local equipment rental yard I go to, and if on the road I'll google equipment rental and find one that sells propane. They usually have nice large yards to get the motorhome in, and the techs generally know what they are doing.