Most RVs have an automatic circuit that charges the house battery when the engine is running (in addition to the engine battery). Many have a momentary contact switch that you can use to connect the house battery to the engine when the engine battery has been run down so you can get your engine started.
If you have a Progressive Dynamics converter with a Charge Wizard, you already have a great setup for your house battery. Just check the water levels and the voltage. First you need to turn the converter off for at least an hour to eliminate the "surface charge." The surface charge is an artificially higher voltage than the battery will have after sitting for awhile. Oh, and make sure there are no drains on it like lights, smoke alarms, etc.
For the engine I recommend this:
NOCO GeniusThis puts out 3.5amps until the battery is charged, then goes into an automatic mode where it monitors the voltage and just switches on when needed. If you are so inclined, you can get auxiliary parts that allow you to permanently mount this charger/maintainer so that it comes on whenever you are connected to shore power or are running the generator (if you have one).
Don't forget to check the water levels in both batteries. With low water levels you can get good voltage readings but there is no real power.
