A solar battery is used to store electricity generated from solar panels, which is necessary part for a complete off-grid solar system. By using a controller, the appliances can work with 110/220V electricity current from the battery.
There are two kind batteries mostly used, lead-acid and gel battery. A lead-acid battery has a shorter lifetime and will pollute environment in some cases but it is cheaper.
A gel battery is environment-friendly and has a longer life, but at a higher price than lead-acid.
Both of them aren't right energy stored material. We hope there will be new batteries with very big capacities, very long lifetimes, small volume and no pollution, and most important, very cheap.