To provide a battery device including a battery; a first cooling system having a first cooling fan and a first temperature sensor; a second cooling system having a second cooling fan and a second temperature sensor; and a controller, wherein the controller carries out abnormality determination with respect to a temperature sensor when a difference between the first cooling air temperature and the second cooling air temperature, detected by the first temperature sensor and the second temperature sensor, respectively, after elapse of a predetermined set period after a start switch of the vehicle is turned off while the first cooling fan and the second cooling fan remain stopped, is equal to or greater than a predetermined amount.