Power supply system, heating control method, and heating control program

A heater heats a battery. A voltage measurement unit measures a voltage of the battery. A temperature measurement unit measures a temperature of the battery. A controller determines that the measured temperature of the battery, which is measured by the temperature measurement unit, is a temperature at which the heater is started, and controls a heating amount from the heater to the battery adaptively according to a voltage difference between the measured voltage during discharging of the battery and a reference voltage. For instance, the controller increases the heating amount as a voltage difference between a discharging lower limit voltage and the measured voltage during low-temperature discharging of the battery becomes small.