BATTERIES Battery is a device which is used to store electrical energy in the form of chemical energy and to transform this chemical energy into electrical energy. The construction of battery consists of electrochemical cells, which consists of two electrodes, negative and positive electrode and an electrolyte in the centre. When the two electrodes are connected by a wire, electrons will flow from negative electrode to positive electrode. This flow of electrons is called electricity.The cell is called dead whenever the electrons on the positive and negative electrodes are equivalent to the electrons produced by chemical reactions and in batteries several different chemical reactions are used For instance, the disposable batteries, is a non-rechargeable energy storage device which once dead must be disposed, example Alkaline batteries. Thus, rechargeable batteries are used so regular replacement is not required. The power stored in battery is used to run the electric motor and other electronic units in an electric vehicle. The batteries are recharged from the dedicated charging unit. TYPES OF BATTERIES The types of rechargeable batteries used in Hybrid Electric Vehicles and Other Electric Vehicles [EV] are Lead-Acid battery. Nickel-Cadmium Battery (NiCd or NiCad) Nickel Metal Hydride [NiMH] battery. Lithium-ion [Li-ion] battery.