To provide a battery pack having a secondary battery suppressing useless power consumption of a control part, and performing charge/discharge more suitable for the battery state by obtaining a temperature history even when the control part cannot monitor the temperature environment of the secondary battery.

To suppress useless power consumption of a control part, a power of the control part is turned off when the voltage of a secondary battery becomes too low. When monitoring the temperature environment of the secondary battery is impossible because of the power of the control part being turned off, temperature-voltage conversion based on the Seebeck effect enables electrical energy according to the temperature environment to be stored in a capacitor. And when the power of the control part is recovered, the capacitor voltage is measured to obtain a temperature history during the control part being turned off based on difference calculated by subtracting a reference voltage from the capacitor voltage or the charged capacitor voltage. The temperature history during the control part being turned off is integrated, and charge/discharge control is performed based on the integrated temperature history.