A nickel metal hydride (NiMH) battery is one of the more recent evolutions in rechargeable batteries. It is superior to a nickel cadmium (NiCad) battery in almost every way except one. NiMH batteries that are not specially treated have a higher electrical discharge rate when not being used. This means a charged battery drains when not in use quicker than a NiCad battery. In general use, however, NiMH batteries last longer than NiCad batteries.