Cooking My RV Batteries

Can you give me some important tips on storing my RV? I park my RV behind my garage and plug in to a 30-amp shore power cord. I have discovered that my battery bank of two, Group 27 batteries are "cooking" and I don't know why. Sure would appreciate any input. Dee S. (Seal Beach, CA)

Dee, aggressive overcharging by the on-board converter/charger would likely be the reason the batteries appear to be “cooking.” Many RV converter chargers are equipped with, what I call, mediocre technology concerning the battery charge function. They serve as outstanding converters (converting AC electricity to DC electricity), but lack the complexity of a processor-controlled battery charger. Many common converters force the maximum amount of current into the battery bank at too high of a voltage rate. Some may taper the amount of amp-hours (current), but it takes special and specific charging algorithms to push the correct amount of current at the correct amount of voltage at a rate that is advantageous to that type of battery, all the while considering its state of charge at that moment in time. 

As a battery charges (accepts and stores amp-hours), the voltage and current rate must constantly be evaluated and modified to ensure that any given battery will not be overcharged or undercharged, yet charged fully. A sophisticated, processor-controlled, three-step charger is needed to accomplish this. I’m a fan of employing the stock converter as a converter only, but to add an aftermarket, multi-step battery charger to be solely in charge of keeping the battery bank(s) fully charged while connected to shore power. The newer technology allows for an RV to be kept plugged in all the time, without the risk of overcharging or “cooking” the batteries in the system. Some are applicable to the various types of RV batteries; wet cell, AGM, gel, etc. I would suggest you upgrade at some point. Until then, if you opt to leave the coach plugged in all the time, be sure to inspect the condition of the batteries every couple of days. Unplug the coach or disable the converter, (simply turn the circuit breaker off), if overcharging or gassing at the batteries is discovered. 

Some RVers have used a timer placed in the AC circuit of the converter to only allow it to operate at certain times. But I’d rather see the stock converter convert and a separate battery charger charge.