Most batteries used in recreational vehicles (RVs) use the same lead acid technology found in other cars and trucks. These batteries utilize traditional flooded cells, glass mats, or gel packs. The two main varieties of RV batteries are deep cycle and starter, which are each useful for different purposes. Campers and trailers usually have a single electrical system, but motorhomes can have coach and engine systems that are somewhat isolated and require separate batteries. There are also two different voltages of RV batteries, though most motorhomes, campers, and trailers operate on 12 volt systems.
The battery technology that is commonly used for both gasoline and diesel powered vehicles is lead acid. These batteries operate by having a number of lead plates suspended in an acid solution. The initial charging process causes oxygen from the acid solution to bind to the cathode and create lead oxide. As the battery discharges, both the anode and cathode plates turn into a lead sulfate. Subsequent charging can reverse this process, and a lead acid battery can undergo a number of these cycles.
Some lead acid batteries are designed to fully discharge before receiving a new charge, so they are referred to as deep cycle. Others are intended to provide a large surge of power and then get topped off. Deep cycle RV batteries are commonly used in all types of motorhomes, campers, and trailers. Since deep cycle RV batteries have thicker lead plates and other modifications, they can provide power throughout a long camping trip, enter a state of deep discharge, and not be damaged. Some of these RV batteries use flooded cells, though more expensive units use gel cell or glass mat technology instead.
Starter batteries are also used in some recreational vehicles. These are very similar or identical to lead acid batteries found in cars and trucks. Since these batteries are not meant to be deeply discharged, they are usually used for the engine electrical system in motorhomes. Many motorhomes have a starter battery for the engine and then two or more deep cycle batteries for the lights and various other accessories in the coach.
Recreational vehicle electrical systems are typically 12v, though 6v RV batteries are sometimes available as well. RVs that have 12v systems can make use of 6v batteries if two are wired in series, which will sometimes have more electrical reserves than a single 12v battery and provide the same voltage. If an RV has space for two 6v batteries but not two 12v batteries, this is one way to obtain a little more reserve power for long trips.