A battery is a device that converts chemical energy directly to electrical energy. It consists of one or more voltaic cells. One half-cell is the positive electrode and the other is the negative electrode. The electrodes do not touch each other but are “connected” by the electrolyte, which can be either solid (gel) or liquid.

Solar batteries are designed for repeated deep discharge and recharge (deep-cycle), unlike automotive batteries which are designed to prove huge amounts of energy for very short times (cold cranking amps). Use of automotive batteries in deep cycle applications will result in rapid failure of these types of batteries. Deep cycle solar batteries generally last many years with proper maintenance.