A battery is a device consisting of one or more electrochemical cells, which store chemical energy and make it accessible in an electrical form. There are many types of electrochemical cells, together with galvanic cells, electrolytic cells, fuel cells, flow cells, and voltaic cells. Formally, an electrical "battery" is an array of similar voltaic cells ("cells") joined in series. However, in many contexts it is universal to call a single cell a battery. A battery's individuality may vary due to many factors including internal chemistry, current drain, and temperature. Generally, battery life can be prolonged by storing the battery in a cool place and using it at an appropriate current.
Although an early form of battery may have been used in ancient times, the development of modern batteries started with the Voltaic pile, invented by the Italian physicist Alessandro Volta in 1800. Since then, batteries have gained recognition as they became portable and useful for many purposes. Unfortunately, the well-known use of batteries has created many environmental concerns, such as toxic metal pollution. Many reclamation companies reprocess batteries to reduce the number of batteries going into landfills. Rechargeable batteries can be charged hundreds of times before draining out; and even after wearing out they can be recycled.
There are two types of batteries disposable and rechargeable both of which convert chemical energy to electrical energy. Disposable batteries can only be used once because they use up their chemicals in an irreversible reaction. Rechargeable batteries can be recharged because the chemical reactions they use are reversible; they are recharged by running a charging current through the battery, but in the opposite direction of the discharge current.