Battery is a device which is used to store the chemical energy and to convert this chemical energy into electrical energy.  The battery is made up of electrochemical cells, which consists of two electrodes, negative and positive electrode and an electrolyte in the center. 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 considered to be dead when the electrons on the positive and negative electrodes are equal. The electrons are generated by chemical reactions and many different chemical reactions are used in batteries. 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.

Refer to know more about the battery and other EV parts.

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.


The types of rechargeable batteries used in Hybrid Electric Vehicles and All-Electric Vehicles [EV] are Lead-Acid batteries,Nickel-Cadmium Battery (NiCd or NiCad), Nickel Metal Hydride [NiMH] batteries and Lithium-ion [Li-ion] batteries. Each battery type has its own advantages and selection of these batteries depends on where it is used so that maximum benefit can be obtained.


It was invented by Gaston Plante, a French Physician in 1859. To convert chemical energy to electrical energy sponge metallic lead and lead peroxide are used in Lead Acid batteries. It is the oldest and the first rechargeable batteries available.

Some of its advantages are low cost, longest life cycle, it can withstand slow, fast and overcharging, available in all sizes and shapes, wide capacity range, low self-discharge-which is lowest among rechargeable batteries, high discharge rate, can be recycled and reused in new batteries.

Some of its disadvantages are energy density is low, poor weight-to-energy ratio, not environmental friendly, transportation restrictions on flooded lead acid, limited number of full discharge cycles.


Waldemar Jungner invented Nickel-Cadmium battery in 1899. The rechargeable NiCd battery is composed of nickel hydroxide in the positive electrode, cadmium in the negative and potassium hydroxide as electrolyte.  A typical lead-acid battery has cell voltage of roughly 2V, which then steadily comes down as it is depleted whereas NiCad batteries will maintain a steady voltage of 1.2v per cell up till it is nearly completely depleted.

Some of the advantages are low internal resistance, wide range of sizes and performance options are available, high charge and discharge rate, lighter, more compact and higher energy density than lead acid batteries, self-discharge rate is lower than NiMH batteries.

Some of the disadvantages are expensive than lead acid, extremely toxic-causes environmental pollution, high self-discharge, low energy densities compared to newer systems.


The Nickel Metal Hydride Battery was patented by Standford Ovshinsky, founder of Ovonics. Hydrogen absorbing alloys are used as the active element at the negative electrode and Nickel -hydroxide at the positive electrode.

Some of the advantages are higher capacity than NiCd, environmental friendly-no toxicity issue, wide operating temperature range, transportation and storage is simple.

Some of the disadvantages are load discharge is high, generates heat during fast charge, sensitive to overcharge.


NiMH and Li-ion came into view in 1990s and Li-ion became the most promising and the fastest growing battery system. Lithium offers the largest energy density and is the lightest of all the metals. Due to safety issues attempts to develop Lithium-rechargeable batteries failed. Thus, there was a shift from Lithium to Lithium-ion, it is safer but lower energy density than Lithium metal. The Sony Corporation in 1991 commercialized the first Lithium-ion battery. The electrodes are made of lightweight lithium and carbon. The Lithium-ion has energy density twice that of Ni-Cad Batteries.

Some of the advantages are no memory and no regular discharge is needed – hence low maintenance, high energy density, can handle more charge/discharge cycles, much lighter than other rechargeable batteries,

Some of the disadvantages are protection circuit is required to maintain voltage and current within safe boundaries, very expensive to manufacture, sensitive to high temperatures.

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