A battery pack is disclosed. The battery pack includes at least one battery, a switch section, a measurement section, and a deterioration level calculation section. The switch section turns on and off charging to the battery. The measurement section measures an open circuit voltage of the battery. The deterioration level calculation section calculates the deterioration level of the battery based on the open circuit voltage measured by the measurement section after the switch section has repeatedly turned on and off the charging 10 times or more.