The battery is a self-contained, chemical power pack that can produce a limited amount of electrical energy wherever it’s needed. Unlike normal electricity, which flows to your home through wires that start off in a power plant, a battery slowly converts chemicals packed inside it into electrical energy, typically released over a period of days, weeks, months, or even years.
E.g.: Zinc-carbon, Alkaline, Button batteries, Lead-acid, Nickel-cadmium, Nickel-metal-hydride (NiMH), Lithium-ion, Fuel cells.