Chemical energy is stored in batteries. A carbon-zinc battery contains acidic material and a rod of zinc down the center. The battery converts a chemical reaction into electrical energy.
Batteries have two ends: positive and negative. When the two ends are connected with wire, a circuit is formed. Electrons then flow through the wire, and an electric current is produced.
A reaction between the chemicals takes place inside the battery. However, the reaction takes place only if there is a flow of electrons. The shelf life of batteries is long because the chemical process doesn't start until the electrons flow through the wire.