One embodiment of present disclosure describes a battery control system including a first string control unit that controls operation of a first battery string and outputs a first serial communication signal, wherein the first serial communication signal comprises a first frequency to indicate that the first string control unit is a master string control unit when a fault is not detected; and a second string control unit that controls operation of a second battery string, receives the first serial communication signal, determines that the second string control unit is a subordinate string control unit when the first serial communication signal comprises the first frequency, and outputs a second serial communication signal, wherein the second serial communication signal comprises a second frequency to indicate that the second string control unit is the subordinate string control unit when a fault is not detected.