Batteries convert chemical energy into electricity. Batteries are made up of one or more separate sections, or cells, containing a chemical called an electrolyte. 

Each cell has two electrically conductive electrodes immersed into its electrolyte. The electrodes are made of different materials; one releases electrons into the electrolyte, and the other absorbs them. 

When an electrical device is connected to the electrodes, an electrical current flows through it and provides electric power for its operation.