Ron750, I have one more tip.
Look in the cabinet above the passenger seat and look for a round 12V outlet. Assuming you have one like we have in our 2007, I advise to buy a simple 12V volt meter that plugs into that outlet. It will display the battery voltage in the motorhome under these various conditions.
1) When parked, living off the power directly from the batteries.
2) When the main Ford engine is running, supplying a charge to the batteries.
3) When the on-board power converter/inverter via the generator or shore power, is supplying a charge to the batteries.
4) When you are charging the batteries using an external battery charger across the battery terminals.
This simple plug-in 12V volt meter quickly reveals the situation with your batteries and the various charging sources.
CLICK HERE for one sold on Amazon.
CLICK HERE for one being sold on eBay.
Batteries in poor health is any voltage under 12V when nothing is utilizing them. As soon as you turn on lights and things, you will see a voltage drop which is normal, but still not drop below 12V. If it does, the batteries need to be charged or replaced.
When the batteries are being charged from the Ford engine, the on-board converter/inverter, or externally, the voltage should read some amount higher than 13V. It will vary depending on what in the house is using battery power at the time.
There is a lot more going on than what I am sharing here. I just put it into simple terms. What might be happening is, you have some kind of unknown power drain. A simple volt meter will reveal that. We previous mentioned your tank heaters being left on by accident. It could be something else left on that you are unaware of. Just having the inverter left on all the time generating 110V inside the rig, is hard on the batteries. I turn on the inverter only when I need 110V, otherwise I leave it off to conserve battery power.