Most RV’s are equipped with two types of batteries, one for engine starting and another that stores reserve energy to power appliances and the electrical systems in the RV (house power). Most campgrounds with RV parking have electrical hook-ups and when connected there’s no worry about draining your house power battery. But as more RV owners venture to primitive sites, having the right kind of battery will keep you from running out of power during your stay.
It’s important to understand that there are different types of batteries that can be installed in RV’s for house power use. The most common is a standard 12-volt automotive starter battery. According to Fred Wehmeyer, Sr. VP of Engineering at U.S. Battery Manufacturing automotive starter batteries are not the best type to use for house power when primitive camping. When you need reserve power to operate lights and appliances in your RV without electrical hook-ups, you need sustained power over a long period of time. Automotive batteries are designed to provide very high current over a very short time to crank the engine, but are not designed to be discharged deeply and will drain quickly when powering the house load. Also, the vehicle’s alternator/regulator charging system is not designed to fully charge batteries that are deeply discharged when used for house power. This type of battery charging requires a dedicated charger that can be connected to AC power and also requires specially designed deep-cycle batteries to withstand the rigors of deep-cycling to provide many hours of reserve energy.
“Deep cycle batteries are a much better choice for RV house power. They are available in both 6 volt and 12-volt sizes that can be connected in multiple series and parallel configurations to provide the amp-hour capacity at 12 or 24 volts, to support the runtime needed in the application,” says Wehmeyer. “Depending on the physical size and the internal design of the battery, battery manufacturers provide ratings on the battery label to indicate the runtime and amp-hour capacity at various discharge rates and times. This allows the user to match the battery voltage and amp-hour capacity to the desired runtime for the specific requirements of the various loads (lights, appliances, etc.) and to select the best deep cycle battery type and configuration for the application.”
If you look at the types of batteries that owners of electric powered golf carts are using, the vast majority are equipped with 6, 8, or 12-volt deep-cycle lead-acid batteries because they provide reliable and cost-effective power over many years of deep-cycle service. “Switching your RV’s house power from an automotive starter battery to a deep cycle, RV/Marine or golf car-type battery will provide greater amp-hour capacity (reserve power) for Overlanding adventures and longer cycle life particularly when sized properly for a maximum of 50 percent depth of discharge (DOD) based on the battery pack’s total amp-hour capacity,” said Wehmeyer.
When discussing deep cycle batteries, there are essentially two types, flooded lead-acid (FLA) and valve-regulated lead-acid (VRLA). There are also two types of VRLA batteries, absorbed glass mat (AGM) batteries and gelled electrolyte (GEL) batteries. FLA batteries require regular maintenance such as checking the electrolyte levels and adding distilled water to the battery cells from time to time. This is to ensure the electrolyte completely covers the cell plates at all times, typically 1/4-inch below the bottom of the fill well of the cell cover.
Sealed VRLA batteries have no free electrolyte in them and do not require water addition. In an AGM battery, the electrolyte is absorbed in a special glass mat separator, and in a GEL battery, the electrolyte is immobilized in a silica gel. Both types of VRLA batteries require special chargers and/or charge algorithms to provide optimum performance and life. They are usually heavier, more expensive, and do not last as long as premium FLA deep cycle batteries.
Deep-cycle lithium batteries are becoming more popular in many applications but Wehmeyer says that the chemistry of lithium batteries requires a battery management system (BMS) to safely control how the battery is charged and discharged. While there are specialized chargers available for lithium batteries, it is not a simple proposition to safely add them to an RV’s electrical system.
As you can see, simply switching from standard automotive starting batteries to deep cycle batteries for your RV’s house power can be very beneficial. Also, if later you find that you need additional runtime or capacity, you can add more batteries or switch to higher amp-hour capacity batteries. Another option is to add solar panels and/or an auxiliary generator to be able to charge the batteries when AC power is not available.