Patent ID: 7339354

Claim:
A rechargeable-battery charging method comprising the steps of: performing pulse charging in which a terminal voltage of a rechargeable battery is compared with a predetermined first set voltage while charging said rechargeable-battery with a constant current and charging is halted after a predetermined first set time elapses when said terminal voltage becomes said predetermined first set voltage or more; measuring an elapsed time An from when the charging is halted and measuring said terminal voltage Bn while the charging is halted; charging said rechargeable-battery for the predetermined first set time where it is determined that said terminal voltage Bn drops to said predetermined second set voltage or less within predetermined second set time; repeating said measuring and charging steps until said terminal voltage Bn does not drop to said predetermined second set voltage or less within said predetermined second set time and determining a number of times n that said rechargeable-battery is charged for the predetermined first set time during a charging cycle; determining a calculated value of said terminal voltage Bn corresponding to a predetermined third set time that is longer than said predetermined second set time, wherein the calculated value accounts for the number of times n that said rechargeable-battery is charged; and repeating said charging where the calculated value of said terminal voltage Bn is said predetermined second set voltage or less and ending said charging where the calculated value of said terminal voltage Bn does not drop to said second set voltage or less.