| abstract |
Provided are a battery pack and a charging system that can easily reduce a risk that a terminal voltage of a secondary battery exceeds an allowable voltage range while diverting a constant voltage charging circuit or a constant current constant voltage charging circuit. A secondary battery 141, 142, 143, a DC-DC converter 36 that supplies a charging voltage for charging the secondary batteries 141, 142, 143, an assembled battery 14, and a DC-DC converter 36 are provided. A switching element Q1 that causes a voltage drop in series with the assembled battery 14, a voltage detection circuit 15 that detects terminal voltages of the secondary batteries 141, 142, and 143, and a terminal voltage that is detected by the voltage detection circuit 15 A voltage drop control unit 213 that increases the on-resistance of the switching element Q1 and increases the voltage drop due to the switching element Q1 when the threshold voltage is equal to or higher than the threshold voltage Vth. [Selection] Figure 1 |