Ni-MH battery is a early alternative product for Ni-Cd battery. It is the most environmentally friendly batteries and no longer use toxic cadmium, which can remove heavy metals on the environment pollution problems. Nickel-metal hydride batteries with greater energy density ratio which can effectively extend the working hours of equipment without additional weight of the digital equipment. What?s more, nickel-metal hydride batteries are similar with nickel-cadmium in the electrical properties. In the actual application, it can replace nickel-cadmium batteries and primary batteries without any need to amend the equipment. Another advantage of nickel-metal hydride battery is that it greatly reduces "memory effect," which makes nickel-metal hydride batteries can be more convenient to use.