A battery is an energy storage device that uses a chemical reaction to do work on charge and produce a voltage between its output terminals. A battery is composed of one or more basic elements known as electrolytic cells (or electrochemical cells) and makes use of an oxidation-reduction reaction. These cells are enclosed in a container and electrically interconnected in an appropriate series/parallel arrangement to provide the required operating voltage and current levels.
Under common usage, the term battery also applies to a single cell if it constitutes the entire electrochemical storage system. An electrolytic cell that produces an external current is called a voltaic cell.