To provide a battery pack in which charge and discharge of a nominal capacitive component for each single cell are possible with long mileage per one charging.

Four lithium ion batteries are connected in series in the battery pack. When the nominal capacitive component for the lithium ion battery is L, lithium ion quantity in a manufacture specification which can be discharged from a positive electrode plate is L1, lithium ion quantity in a manufacture specification which can be stored to a positive electrode plate is L2 and charged state of one of the four lithium ion batteries is SOCi, the battery pack is constituted so that all four of the lithium ion batteries are in conditions fulfilling C=100×(L2-L1)/L, ¾(ΣSOCi)/4-SOCi¾COPYRIGHT: (C)2005,JPO&NCIPI