The Ni-Mh battery is a new type of battery, which is better than the lead-acid battery. It is lighter, more efficient, inner resistance is only 1/10 of lead-acid battery, and the life-span is 2.5 times more than lead-acid battery. In addition, it is not like lead-acid battery may cause lead pollution when dispose Ni-Mh battery. Although lead-acid battery is cheap, It will be replaced by Ni-Mh battery in future.