A power-supplying battery of an electric vehicle includes a plurality of chargeable batteries that are grouped into at least two first battery groups, and the chargeable batteries of each first battery group are divided into at least two second battery groups that are electrically connected in parallel. Each first battery group is electrically connected to each other in parallel to form a complete set of the power-supplying battery. During charging of the power-supplying battery, an external charging power source is set in electric conduction with the power-supplying battery and a current or a voltage of the charging power source is supplied, in a divided manner, to charge each first battery group and the second battery groups thereof. During discharging of the power-supplying battery, a voltage or a current of each first battery group is combined with each other for output as a total.