A battery pack (2000) includes a battery (2020), a contact-type switch (2040), a control unit (2060), and a sensor (2080). The battery pack (2000) is connected to a charger (10) through an electric power line (30). The battery (2020) is charged with a charging current supplied from the charger (10). The battery pack (2000) is connected to a load (20) through an electric power line (40). The contact-type switch (2040) is provided between the charger (10) and the battery (2020). The control unit (2060) turns off the contact-type switch (2040) in a case where a value detected by the sensor (2080) is equal to or smaller than a reference value decided based on specifications of the contact-type switch (2040).