Q. Someone recommended that I install a trickle charger to keep my starting battery fully charged when we are staying long-term at a campground. Is that a good accessory to get?
A. That depends. What starter batteries don’t like is being connected to the RV’s converter and being constantly charged at the same rate and voltage as the house batteries.
Some motorhome owners may think that adding a wire between the RV’s house batteries and the vehicle starter battery would be a good idea because it would allow the starter battery to also be charged by the converter. However, such a modification will overcharge the starter battery and eventually damage it.
If you wish to keep your starter battery up to charge during a long storage period or campsite stay, it is perfectly acceptable to use a small “trickle charger” or “battery maintainer” to maintain the charge on your starter battery.
These devices are designed to only provide a very small charge at a relatively low voltage. They won’t charge a depleted battery, but they will maintain the charge on a fully-charged battery.
I have also learned that some motorhome manufacturers provide a regulated battery maintainer system that will maintain the charge on the starter battery when the coach is plugged into A/C power. You can determine if your coach has such a system by measuring the starter battery voltage with a meter when the RV is plugged into AC power and has sat idle for at least a day.
Starter batteries will normally come to a resting voltage of 12.7 volts or less if there is no charger attached to them. A trickle charger will raise that voltage to above 12.8V, so if you read a higher voltage on your starter battery, it is likely that your rig provides some sort of maintenance charge to your starter battery by design.
Remember to check electrolyte levels in all of your batteries regularly, and top them up with distilled water