Patent ID: 8228042

Claim:
A battery pack charging method for charging a battery pack having a plurality of lithium ion rechargeable batteries connected in series to a full charge by using a constant current charging and a constant voltage charging, the method comprising: performing the constant current charging until a total battery pack voltage reaches a prescribed total voltage; switching from the constant current charging to the constant voltage charging after the total battery pack voltage reaches the prescribed total voltage, until a full charge is reached; detecting a voltage of each of the plurality of lithium ion rechargeable batteries being charged; and switching from the constant voltage charging or the constant current charging to a pulse charging after the voltage of any of the plurality of lithium ion rechargeable batteries exceeds a first specified voltage, such that prior to switching to the pulse charging, the constant current charging and the constant voltage charging are repeatedly performed until the voltage of any of the plurality of lithium ion rechargeable batteries has a voltage that exceeds the first specified voltage, wherein during pulse charging, when the voltage of any of the plurality of lithium ion rechargeable batteries has exceeded the first specified voltage and a first specified time has elapsed, and when the voltage of any of the plurality of lithium ion rechargeable batteries has exceeded a second specified voltage, which is higher than the first specified voltage, and a second specified time has elapsed, charging is suspended, and charging is re-started after an interval or a third specified time has elapsed and the voltage of all the batteries has dropped below the first specified voltage.