Am charging my two 6-volts with my sears battery charger. I have the Ground wire taken off. Was also putting water on board, so I checked the lights on the monitor for water level, and my battery level shows full, even with the ground wire off the battery's. But I have the shore cord plugged in to run the frig. on electric. Next I'll take the plus wire off and see what, if any of the lights come on for the battery. I know most monitors don't read right. But this had me puzzled. waam Holland, Mich.

 

You need to disconnect from shore power and unplug the charger to get an accurate(ish) reading. Mine reads full also when on shore power, even when the batteries are dead. I'm guessing the charge is checked at the converter, and shore power confuses it to thinking the battery is fully charged.

 

The battery meter on the wall is usually connected at the closest 12volt wire to the meter which is usually the one that goes from the converter to the battery. So when ever you are hooked to shore power it will read full charge.

 

Thanks Ptgarcia, I'll do what you said. Diesel is 2.84 to 2.88 here in Holland. waam Holland, Mich.

 

You need to be careful when working with your batteries. Pulling the wires on & off when connected can cause a spark. If you have been charging, you may have hydrogen gas + spark= BOOM.
So, you can charge plugged in & with a charger, but proably best to check the batties when not plugged in to anything. A volt meter will give better information.