Patent ID: 8143854

Claim:
A method of adjusting a battery pack including a plurality of secondary batteries divided into a first battery group and a second battery group according to charge levels before adjustment so that the first battery group includes one or more secondary batteries each having a high charge level and the secondary group includes two or more secondary batteries each having a lower charge level than that of the first battery group, the method being adapted to reduce a difference in charge level between the one or more secondary batteries of the first battery group and the two or more secondary batteries of the second battery group, the method comprising: a first adjusting process for discharging the one or more secondary batteries of the first battery group so that the charge level of the one or more secondary batteries of the first battery group falls within a charge level range determined based on the charge level of the two or more secondary batteries of the second battery group; and a second adjusting process for discharging all the secondary batteries of the first and second battery groups by a same electric quantity, respectively, to reduce a battery voltage difference between the one or more secondary batteries of the first battery group and the one or more secondary batteries of the second battery group, wherein the rate of discharge of the battery voltages of the first battery group is different than the rate of discharge of the battery voltages of the second battery group during the second adjusting process, and the plurality of secondary batteries of the battery pack are electrically connected in series to each other.