BATTERY ABNORMALITY WARNING METHOD AND BATTERY ABNORMALITY WARNING DEVICE

A battery abnormality warning method involves detecting an abnormality in a vehicle-mounted battery and warning an occupant in the vehicle. The battery abnormality warning method determines whether a pressure abnormality has occurred in the battery based on an air pressure inside a battery pack of the battery. The battery abnormality warning method further determines whether a voltage abnormality has occurred in the battery based on a cell voltage of the battery. An abnormality is determined to have occurred in the battery when both a pressure abnormality in the battery and a voltage abnormality in the battery are determined to have occurred within a prescribed time period. A warning is outputted to the occupant in the vehicle upon determining that an abnormality has occurred in the battery.