The present invention provides enhanced serial communication reliability in a situation where a plurality of cell controllers and a battery controller are daisy-chained to form a serial communication configuration. While the plurality of cell controllers and the battery controller are daisy-chained to form a serial communication configuration, the battery controller or each cell controller includes a communication speed detection means, which detects the communication speed of data input from an additional controller, and a reception timing correction means, which corrects the reception timing for data input from the additional controller in accordance with the communication speed detected by the communication speed detection means.