A battery management system includes a monitoring device and a controller. The monitoring device is arranged in a housing accommodating a battery, monitors the battery and acquires battery monitoring information that includes information indicating a state of the battery. The controller performs wireless communication with the monitoring device and execute a predetermined process based on the battery monitoring information. The controller transmits a request for battery monitoring information to the monitoring device. The monitoring device transmits the battery monitoring information to the controller in response to the request. The controller determines whether missing of the battery monitoring information has occurred based on a correlation between the battery monitoring information acquired from the monitoring device via wireless communication and relationship information held by the controller related to the battery monitoring information.