A semiconductor device that inhibits deterioration of a secondary battery is provided. The semiconductor device includes a secondary battery module and a first circuit. The secondary battery module includes a secondary battery and a sensor. The first circuit includes a variable resistor. The sensor has a function of measuring a temperature of the secondary battery. The first circuit has a function of judging the charge voltage of the secondary battery and outputting a first result; a function of judging the temperature of the secondary battery measured by the sensor and outputting a second result; a function of determining the magnitude of the variable resistor on the basis of the first result and the second result; a function of discharging the charge voltage through the variable resistor; and a function of stopping discharge when the charge voltage reaches a specified voltage.