There are many types of solar power rechargeable batteries on the market. Most well researched and old proved technology is lead acid batteries. They will deliver the best capacity for the buck. Disadvantages of such batteries are big size and weight. If it is for your RV that size and weight is not that big of a deal.
Car batteries is a good example of lead acid batteries, but they are not good for storing solar energy, because they are designed to give a large burst of power for a short time. Batteries you need should provide continious low to moderate flow of electricity. This type of batteries is called “deep cycle” battery. Deep cycle means discharging battery for 80% or more and then charging it back. If you do it with your car battery it will die after 20 deep cycles or so. True deep cycle batteries can handle up to 800 deep cycles.
Lead acid deep cycle batteries for solar power systems are available in several modifications. The oldest and cheapest design is called a flooded battery. It has a liquid sulfuric acid inside as a working body. If you overcharge such battery it will bubble gas (hydrogen and oxygen) and you will have to add distillic water to compensate it. Hydrogen and oxygen mix is quite dangerous, so you really should watch for your batteries and use good battery chargers which protect your batteries from overcharging.
New safer design is called AGM (or sometimes sealed maintenance free) batteries. These are the best batteries for solar power, they are sealed (as you can guess from the name) and you don’t have to add any water in them (thus maintenance free). They can withstand a bit of overcharging, that’s why they are safer. The downside — they cost a bit more than flooded batteries, but serve as perfect residential solar power batteries, because they are safer.