Patent ID: 7609034

Claim:
A battery system, comprising: a battery pack having a plurality of electrically connected unit cells including a first unit cell and a second unit cell that are substantially identical to one another and are electrically connected to one another, wherein the battery pack is configured such that the second unit cell dissipates heat more readily than the first unit cell; a temperature detecting unit which detects a temperature of each of the first and second unit cells; and a charge control unit configured to charge the first unit cell to a state of charge or open cell voltage determined according to the temperature of the first unit cell and to charge the second unit cell to a state of charge or open cell voltage determined according to the temperature of the second unit cell, such that the first unit cell is charged to a state of charge or open cell voltage that is less than that of the second unit cell and such that the first unit cell and the second unit cell degrade at a similar rate.