A control unit for a vehicle battery controller including a sensor configured to acquire information comprising a current, a voltage, and a temperature of a subordinate battery configured to back up a main battery during autonomous driving; wherein the control unit is configured to: control charging and discharging of the subordinate battery based on the information acquired by the sensor; tentatively determine, by executing a first battery control during a period of the manual driving after an ignition is turned ON, whether the subordinate battery is able to output backup power necessary during a limp home mode of the autonomous driving; permit the autonomous driving when determination is made, through the first battery control, that the subordinate battery is able to output the backup power; execute the autonomous driving in response to a request after the autonomous driving is permitted; and determine, by executing a second battery control after the autonomous driving is permitted, whether the subordinate battery is able to output the backup power, the second battery control taking longer time than time of the first battery control, characterized in that the control unit is configured to, as the first battery control: execute charging and discharging of the subordinate battery in a first time; calculate a resistance value of the subordinate battery based on changes in the current and the voltage during the charging and discharging; estimate whether a first temperature of the subordinate battery is lower than a first reference temperature, the first temperature being obtained based on the calculated resistance value under a condition that a resistance value and a power storage amount necessary for backup are satisfied; and determine that the subordinate battery is able to output the backup power when estimation is made that the first temperature of the subordinate battery is lower than the first reference temperature. wherein the control unit is configured to: control charging and discharging of the subordinate battery based on the information acquired by the sensor; tentatively determine, by executing a first battery control during a period of the manual driving after an ignition is turned ON, whether the subordinate battery is able to output backup power necessary during a limp home mode of the autonomous driving; permit the autonomous driving when determination is made, through the first battery control, that the subordinate battery is able to output the backup power; execute the autonomous driving in response to a request after the autonomous driving is permitted; and determine, by executing a second battery control after the autonomous driving is permitted, whether the subordinate battery is able to output the backup power, the second battery control taking longer time than time of the first battery control, control charging and discharging of the subordinate battery based on the information acquired by the sensor; tentatively determine, by executing a first battery control during a period of the manual driving after an ignition is turned ON, whether the subordinate battery is able to output backup power necessary during a limp home mode of the autonomous driving; permit the autonomous driving when determination is made, through the first battery control, that the subordinate battery is able to output the backup power; execute the autonomous driving in response to a request after the autonomous driving is permitted; and determine, by executing a second battery control after the autonomous driving is permitted, whether the subordinate battery is able to output the backup power, the second battery control taking longer time than time of the first battery control, characterized in that the control unit is configured to, as the first battery control: execute charging and discharging of the subordinate battery in a first time; calculate a resistance value of the subordinate battery based on changes in the current and the voltage during the charging and discharging; estimate whether a first temperature of the subordinate battery is lower than a first reference temperature, the first temperature being obtained based on the calculated resistance value under a condition that a resistance value and a power storage amount necessary for backup are satisfied; and determine that the subordinate battery is able to output the backup power when estimation is made that the first temperature of the subordinate battery is lower than the first reference temperature. execute charging and discharging of the subordinate battery in a first time; calculate a resistance value of the subordinate battery based on changes in the current and the voltage during the charging and discharging; estimate whether a first temperature of the subordinate battery is lower than a first reference temperature, the first temperature being obtained based on the calculated resistance value under a condition that a resistance value and a power storage amount necessary for backup are satisfied; and determine that the subordinate battery is able to output the backup power when estimation is made that the first temperature of the subordinate battery is lower than the first reference temperature.