Patent ID: 7737659

Claim:
A battery charging method that charges a battery to a full charged state at a specified voltage repeatedly, wherein the specified voltage decreases as battery charging/discharging processes are repeated by counting a number of predetermined charging and discharging cycles, the method comprising: repeating charging of the battery in which the battery is charged at a first constant voltage during a first predetermined charging and discharging cycles; repeating charging of the battery in which the battery is charged at a specified voltage that decreases from the first constant voltage gradually and continuously as the cycle number is counted during a second predetermined charging and discharging cycles following the first predetermined charging and discharging cycles; and repeating charging of the battery in which the battery is charged at a second constant voltage which is lower than the first constant voltage during a third predetermined charging and discharging cycles following the second predetermined charging and discharging cycles, wherein the number of predetermined battery charging and discharging cycles is counted, and the specified voltage decreases as the counted predetermined number of battery charging and discharging cycles increases, and in the repeated charging of the battery in which the battery is charged at the specified voltage that decreases, the specified voltage decreases at a constant rate and until the end of the second predetermined charging and discharging cycles.