The Nickel Metal Hydride(NiMH) batteries are a type of rechargeable batteries that is quite similar to nickel-cadmium (NiCd) battery, but unlike the NiCd batteries, the NiMH batteries have a hydrogen-absorbing alloy as the anode instead of using cadmium. The abbreviation NiMH is commonly used for Nickel Metal Hydride batteries. In this cell, nickel plays the role of the cathode, similar to that of NiCd cells. The Nickel Metal Hydride(NiMH) batteries can possess two or three times the capacity than an equivalent size NiCd battery and the memory effect is not so significant. But, if compared to the lithium-ion battery, the volumetric energy density of Nickel Metal Hydride(NiMH) batteries is lower and the self-discharge capability is higher.
The specific energy density of NiMH material is nearly 70 W·h/kg (250 kJ/kg), along with a volumetric energy density of about 300 W·h/L. The common penlight-size (AA) cells possess nominal capacities C that ranges from1100 mA·h to 2700 mA·h at 1.2 V. Usually they are rated at 0.2×C rate. Although discharge capacity is considered to be an inverse function of the discharge rate, but till 1×C rate nearly, there is no such significant difference.
| According to the history of Nickel Metal Hydride(NiMH) batteries the NiMH technology was invented by Stanford Ovshinsky. In the mid-1980s the first consumer grade NiMH batteries started to appear.
In the year 1994, Ovshinsky’s company, ECD Ovonics entered into partnership ties with General Motors in order to develop high performance Nickel Metal Hydride(NiMH) batteries for GM’s Ev1 electric car. Presently, the NiMH technology has been licensed by Cobasys - a joint venture between ECD Ovonics and Chevron Corporation. The applications of NiMH batteries include hybrid vehicles like Honda Insight/Civic or Toyota Prius, plus consumer electronics. |
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