Q. We own a 25-foot 2000 Coachmen Catalina Lite trailer and leave it hooked to a shore line to keep the batteries charged. For the past two years, under these conditions, the batteries have gone dry in about 2-1/2 months. I brought the camper back to the dealer last winter to have this checked. A representative there told me that everything checked out fine. Any suggestions?
— L.C., Bedford, Virginia
A. To prevent batteries from gassing excessively and boiling out the water, converter or inverter chargers with more sophisticated circuitry go into a “float” stage where the voltage is reduced to around 13.2. Many rigs are outfitted with converters that provide voltage in the range of 13.8 to 14 volts, which can be too high for long-term storage. If your rig has one of these converters, the simplest solution is to use a small maintenance charger that will switch to a float mode when the batteries are charged.
Unplug the coach’s power cord when you do this, or disconnect the converter so it won’t work at the same time. If you have two 12-volt batteries connected in series, charge them both from one charger. Run an extension cord from the house to power the charger.
Ken Freund’s more than three decades of auto-repair experience and 20-plus years of RVing helped him author numerous books and articles on vehicle repair. In addition to RV Clinic and Performance, he writes the Powertrain column in MotorHome magazine. Ken has been a California Automotive VO-Tech and Smog-Test Program Instructor and an ASE-certified Master Automobile Technician.