Maintaining RV batteries

Depending on how low your batteries are you can fill them and use the maintainer during the winter. If your batteries have been boiled out they may need replaced. Only a refill, charge, and test will tell. Look up "battery isolator" on the net and see what they look like. Your battey cables will all be attached. Usually they are under the hood.

Oh ok. We went and had all three batteries replaced, so they are all new. I just wanted to prevent it from happening again.

What does the battery isolator do?