A communication method comprising: performing bidirectional communication between a master controller and first to N th (where N is an integer equal to or more than two) slave controllers (2100, 2200, 2300) through a first communication channel, the master controller being connected to the first to N th slave controllers through the first communication channel in parallel, the first to N th slave controllers being respectively connected to first to N th battery cells (4100, 4200, 4300), each of the first to N th slave controllers being configured to transmit voltage information data or temperature data of the battery cell to which it is connected to the master controller through the first communication channel, receiving, by the master controller, an indication signal through a second communication channel via the first to N th slave controllers, the master controller being serially connected to the first to N th slave controllers through the second communication channel in a daisy chain manner, the indication signal indicating whether at least one of the first to N th battery cells is normal or abnormal in voltage or temperature, the indication signal being a first indication signal when the first to N th battery cells are normal or a second indication signal when at least one of the first to N th battery cells are abnormal, wherein: if first to N th slave controllers input the first indication signal through the second communication channel and determine that first to N th battery cells are normal then first to N th slave controllers output the first indication signal to the second communication channel; if first to N th slave controllers input the first indication signal through the second communication channel and determine that first to N th battery cells are abnormal then first to N th slave controllers output the second indication signal to the second communication channel; if first to N th slave controllers input the second indication signal through the second communication channel then first to N th slave controllers output the second indication signal to the second communication channel. performing bidirectional communication between a master controller and first to N th (where N is an integer equal to or more than two) slave controllers (2100, 2200, 2300) through a first communication channel, the master controller being connected to the first to N th slave controllers through the first communication channel in parallel, the first to N th slave controllers being respectively connected to first to N th battery cells (4100, 4200, 4300), each of the first to N th slave controllers being configured to transmit voltage information data or temperature data of the battery cell to which it is connected to the master controller through the first communication channel, receiving, by the master controller, an indication signal through a second communication channel via the first to N th slave controllers, the master controller being serially connected to the first to N th slave controllers through the second communication channel in a daisy chain manner, the indication signal indicating whether at least one of the first to N th battery cells is normal or abnormal in voltage or temperature, the indication signal being a first indication signal when the first to N th battery cells are normal or a second indication signal when at least one of the first to N th battery cells are abnormal, wherein: if first to N th slave controllers input the first indication signal through the second communication channel and determine that first to N th battery cells are normal then first to N th slave controllers output the first indication signal to the second communication channel; if first to N th slave controllers input the first indication signal through the second communication channel and determine that first to N th battery cells are abnormal then first to N th slave controllers output the second indication signal to the second communication channel; if first to N th slave controllers input the second indication signal through the second communication channel then first to N th slave controllers output the second indication signal to the second communication channel. if first to N th slave controllers input the first indication signal through the second communication channel and determine that first to N th battery cells are normal then first to N th slave controllers output the first indication signal to the second communication channel; if first to N th slave controllers input the first indication signal through the second communication channel and determine that first to N th battery cells are abnormal then first to N th slave controllers output the second indication signal to the second communication channel; if first to N th slave controllers input the second indication signal through the second communication channel then first to N th slave controllers output the second indication signal to the second communication channel.