Re: RV Batteries
Well, first read the manual. If it doesn't say, or you want to check, there are ways of putting guages and meters and all kind of technical stufrf, but the 'easiest' way would be to have the batteries 'weak' and take it for a drive. If they are then 'charged' you have your answer, and unlike the manual, even know that it is working.
By the way, there are '3' ways to measure the state of a battery. The first is by sticking a hygrometer into each cell and sucking out a bit of the fluid. This will show you if you have a 'bad' cell, and give you an average view of the batteries' state. Next, you can measure the voltage. This will tell you if it is charging, and might give some indication of a significant problem. Finally, is a load test. This is looking at the voltage while a heavy load is placed on the battery. This really tells you what the battery can do.
In addition, some of the fancier RVs have 'smart' battery monitors which keep track of the batteries usage and provide a computed 'state' for the batteries.