A battery management system, comprising: a plurality of the battery management units (10-1..10-N), each battery management unit includes a first terminal, a second terminal, a memory unit and a control unit; and a serial communication line which connects the plurality of battery management units through their first and second terminals; characterized in that for each battery management unit: the memory unit stores a fundamental frequency and an additional frequency value; the control unit is configured to: set a status of the control unit as a master unit when frequency of a wakeup signal received through the first terminal corresponds to the fundamental frequency stored in the memory unit; set the status of the control unit as a slave unit, determine how many numbers of additional frequency values are added to the fundamental frequency in the frequency of the wakeup signal received through the first terminal and set this as a communication identifier of the control unit when frequency of the wakeup. signal received through the first terminal fails to correspond to the fundamental frequency stored in the memory unit; output through the second terminal a further wakeup signal with a frequency being the sum of the frequency of the wakeup signal received through the first terminal and the additional frequency value stored in the memory unit after the control unit sets the status of the control unit, the further wakeup signal being received by the battery management unit (10-1..10-N) next in line in the serial communication line through its first terminal. a plurality of the battery management units (10-1..10-N), each battery management unit includes a first terminal, a second terminal, a memory unit and a control unit; and a serial communication line which connects the plurality of battery management units through their first and second terminals; characterized in that for each battery management unit: the memory unit stores a fundamental frequency and an additional frequency value; the control unit is configured to: set a status of the control unit as a master unit when frequency of a wakeup signal received through the first terminal corresponds to the fundamental frequency stored in the memory unit; set the status of the control unit as a slave unit, determine how many numbers of additional frequency values are added to the fundamental frequency in the frequency of the wakeup signal received through the first terminal and set this as a communication identifier of the control unit when frequency of the wakeup. signal received through the first terminal fails to correspond to the fundamental frequency stored in the memory unit; output through the second terminal a further wakeup signal with a frequency being the sum of the frequency of the wakeup signal received through the first terminal and the additional frequency value stored in the memory unit after the control unit sets the status of the control unit, the further wakeup signal being received by the battery management unit (10-1..10-N) next in line in the serial communication line through its first terminal. the memory unit stores a fundamental frequency and an additional frequency value; the control unit is configured to: set a status of the control unit as a master unit when frequency of a wakeup signal received through the first terminal corresponds to the fundamental frequency stored in the memory unit; set the status of the control unit as a slave unit, determine how many numbers of additional frequency values are added to the fundamental frequency in the frequency of the wakeup signal received through the first terminal and set this as a communication identifier of the control unit when frequency of the wakeup. signal received through the first terminal fails to correspond to the fundamental frequency stored in the memory unit; output through the second terminal a further wakeup signal with a frequency being the sum of the frequency of the wakeup signal received through the first terminal and the additional frequency value stored in the memory unit after the control unit sets the status of the control unit, the further wakeup signal being received by the battery management unit (10-1..10-N) next in line in the serial communication line through its first terminal. set a status of the control unit as a master unit when frequency of a wakeup signal received through the first terminal corresponds to the fundamental frequency stored in the memory unit; set the status of the control unit as a slave unit, determine how many numbers of additional frequency values are added to the fundamental frequency in the frequency of the wakeup signal received through the first terminal and set this as a communication identifier of the control unit when frequency of the wakeup. signal received through the first terminal fails to correspond to the fundamental frequency stored in the memory unit; output through the second terminal a further wakeup signal with a frequency being the sum of the frequency of the wakeup signal received through the first terminal and the additional frequency value stored in the memory unit after the control unit sets the status of the control unit, the further wakeup signal being received by the battery management unit (10-1..10-N) next in line in the serial communication line through its first terminal.