Batteries can be classified under two major categories:

  1. Primary Batteries

Primary Batteries are non-rechargeable batteries. Once these batteries are completely discharged, they can not be recharged. The electrochemical reaction within these batteries cannot be reversed. They need to be recycled. The devices that use primary batteries generally consume lesser energy so that the battery lasts longer, for example, wristwatches, toys, remote controllers, pacemakers etc. Alkaline batteries are the best example for primary batteries. The best part of alkaline batteries is that they are harmless to the environment, they are less expensive and they do not leak while being fully discharged. However, since alkaline batteries have low power load, they can support only those devices that require low power like remote controllers, flashlights, etc.

  1. Secondary Batteries

Secondary batteries are rechargeable batteries that can be recharged once the energy drains out. The electrochemical reaction in these batteries can be reversed by applying a certain voltage in the reverse direction. These batteries are used in devices that require higher amounts of energy. Secondary batteries come in a small capacity, as well as heavy capacity. The small capacity batteries are used to power portable devices like mobile phones etc., and heavy capacity secondary batteries are used in high power draining devices like electric vehicles, etc. They are also used in inverters. There are four major types of secondary batteries: Lithium-ion(Li-ion), Nickel Cadmium(Ni-Cd), Nickel-Metal Hydride(Ni-MH) and Lead-Acid.