From the bloggers at Everything About RVing.
Does my RV have the wrong type of house battery?
Can regular 12 volt car batteries be used as house batteries? Yes, they can, but are they the best choice? No, they are not. Since you are already changing out the batteries in your RV, I would suggest that you use two Deep Cycle 6 volt batteries as your new house battery setup.
Take a look at the battery type information below to see why I recommend true deep cycle batteries as house batteries.
Starting or Cranking Battery: Just as its name implies it is a battery that is designed to crank over an engine to get it started. It provides a powerful short burst of energy and is not designed to provide power for a long period of time. It is also not designed to be discharged and recharged often; the life span of this battery will be greatly reduced if it is used to power the 12 volt system of a 5th Wheel. It will also not provide power for as long as a Deep Cycle Battery.
To read the full story by Everything About RVing, click here.