Friday, August 28, 2009

NiMH Batteries in a Nutshell

NiMH is the abbreviation for Nickel-metal hydride batteries. These are known as the secondary or the rechargeable type of electrochemical devices. They are very similar to Nickel hydrogen cell. The only difference between the two is that instead of cadmium, hydrogen is used as the active element in NiMH batteries at the negative electrode. NiMH batteries were first introduced in the market in 1989. A NiMH cell offers an operation value of two to three times higher than the equivalent size Nickel-cadmium battery. These cells provide an average output voltage of 1.2 Volts.

The working of the nickel-metal hydride cell is based on the simple concept developed in 1970s. It was observed that certain types of metallic alloys were capable of capturing and releasing Hydrogen in volumes thousand times their own. This research demonstrated that stored hydrogen could be used as an alternative source of energy. Further experiments were carried out using differing proportions of alloy constituents to balance the thermodynamic equation during the absorption and release process, under room temperatures and pressures.

The technology has greatly evolved since then and today the NiMH batteries have found its utility in high voltage automobile applications. These cells have an energy density twice that of Lead acid and nearly 40% higher than that of NiCads. Although the NiMH batteries are a little expensive, they are considered to be better for the environment.

Owing to the several advantages offered by the NiMH batteries almost every specialized automobile under production today makes use of them. In order to meet this increasing demand, many leading companies have a specialized R&D department devoted to the development of high-performance and superior quality NiMH batteries. Some brands of NiMH batteries have gained high reliability among the consumers and are widely used in EV/HEV and other places like the scooter, e-bike and motorcycle.

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