We have a 2002 Rexhall Rex Air 36-foot motorhome. The deep-cycle coach batteries have some sort of drain on them, even when we are plugged into a shoreline. We’ve tried disconnecting them via the switch, and leaving them connected with the same results. We have had service departments check it out and they find no drain. What is going on?
John Thompson | Dallas, Texas
Seems like it may be the batteries. Rather than using the switch, try disconnecting the batteries by removing a negative battery cable from each one. Make sure the terminals and tops of the batteries are clean and dry. Fully charge each battery with a battery charger, and then test each cell with a hydrometer. With the batteries completely disconnected, hydrometer test them every few days. If they don’t discharge rapidly, the problem is in the circuit. However, if they still go down, the batteries with the bad cell readings are defective and should be replaced.
— Ken Freund