[Foldbak]

Originally Posted by phillyg

You said,, "Several 'auto' mechanics have told me that batteries with volts below 12.1 volts are dead. That maybe false." I've heard similar, yet I've had two sets of batteries in fifthwheels get drained down to nearly nothing, and I've charged and used them for a long time. The current set is two years from the last drain down and still strong. I'm now using a small solar panel while in storage.

WRT a dealership, "'Thinking' about just selling the fifth wheel since there is no decent dealership near by." After an RV is past the warranty period, I try never to use any dealership for repairs. I'd rather DIY it or call in mobile service if I can't do something.

Google is our friend
A typical 12-volt auto battery will have around 12.6 volts when fully charged. It only needs to drop down to around 10.5 volts to be considered fully discharged. If it drops down below that, the battery will become damaged due to excessive sulfation.
As a general rule.