Battery seem evaporating much too fast

[Nutravlr]

Endura Chevy 5500. Two batteries. The battery toward the compartment door has water evaporating. I fill, and in a week it is back to plates being without water on the top of the plates. I am plugged into shore. I should think this is not normal, but never having had a motorhome before, am not sure if normal or due to me leaving connected to shore or other. Normal or problem or I am using the system improperly (i.e. connected to shore without using the RV or some switch I should be throwing)?

Thanks.

[Fliptop]

better try to change some switch.

maybe they are not functioning well

[RayChez1]

Check your batteries with a hydrometer. It sounds to me like you might have a shorted out cell on one of the batteries and the charger just keeps charging at a high rate and is evaporating the water.
Definitely something wrong, it shouldn't boil the water out that soon.

[Nutravlr]

Thanks. Motorhomes of Texas diagnosed the problem as you, shorted cell, and replaced both batteries for no charge since they felt that they should have caught the problem in selling the RV. Thanks for your time.