Solar batteries are really deep cycle batteries that provide energy storage for solar, wind and other renewable energy systems. Different from a car battery, a deep cycle battery is capable of surviving prolonged, repeated and deep discharges which are typical in renewable energy systems that are “off grid” (disconnected from the electric utilty company).
In renewable energy systems, deep cycle batteries provide the energy storage for your system. Unlike your car battery, deep cycle batteries that are used in renewable energy applications are meant to be discharged and recharged (cycled) repeatedly. To maintain healthy batteries and prolong battery life, most manufacturers suggest limiting the depth of discharge to about 20%. (That means the deep cycle batteries will be at 80% capacity or better.) At the very least, do not allow the batteries to be discharged below 50% Depth of Discharge (DOD)