BATTERY SYSTEM WITH TEMPERATURE RAISING

A battery system (10) includes: a power detector that detects output power from an external power source (100); a charging mechanism (30, 32, 34) that charges a main battery by external power; a temperature raising mechanism (26) that raises a temperature of the main battery to a temperature not lower than a reference temperature; and a controller that controls the charging mechanism (30, 32, 34) and the temperature raising mechanism (26), wherein when the detected output power is lower than a reference power, the controller prohibits a temperature raising process with an SOC of the main battery lower than a charge reference value and performs a charging process.