Storage battery technology continues to develop, as the need for a reliable, cost effective storage solution becomes more critical with the continued expansion of solar and wind power generation. Batteries are the heart of all off-grid and back-up wind/solar systems. Their function is to balance the outgoing electrical requirements with the incoming power supply. They offer a reliable source of electricity which can be used when solar or wind power is not available. Batteries are able to provide short term power output many times higher than the charging source output.

For renewable energy storage, a deep cycle battery is required. 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.

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). Often an inverter will have a Low Voltage Disconnect feature that will disconnect loads at a given set point. Low voltage alarms can provide audible warnings as well.