Ask The RV Doctor – by Gary Bunzer
Q: Dear Gary, Is there a way to charge my two 6-volt batteries with a regular stand-alone battery charger? If so, how would you hook up the positive and negative charger clamps?
—George Pimentel, Fresno, California
A: George, I’m going to assume you are referring to a standalone battery charger that is 12-volts only. I mention this because some shop chargers are equipped with a 6-volt output option as well as 12-volt output. Since all DC components on RVs operate on 12-volt, (water pump, fans, lamps, etc.), your two 6-volt batteries, as installed, are still set up to produce a 12-volt final output. The only difference is the connection between the two batteries. At the root level, two 6-volt batteries are wired in “series” and two 12-volt batteries are wired in “parallel” in order to produce 12 volts final output. Take a look at the diagrams shown here; the final output that provides battery power to the components on the RV is still 12 volts DC. Therefore, both configurations can be charged by any 12-volt battery charger by simply connecting the charger’s red cable clamp to the “plus” 12-volt terminal lead and the black or ground cable clamp to the negative terminal as shown here. But a word of caution! Notice on the 6-volt battery diagram, you must know which battery feeds the positive voltage to the RV and which battery represents the negative connection. If your series-connected batteries look similar to those on the right side of this diagram, then all you do is connect them as shown. If yours are wired differently, do let me know and we’ll investigate further. Bottom line: 12 volts is still 12 volts. You do not want to connect either battery charger lead to the posts that make the interconnection between the two 6-volt batteries.
