A telecommunication system comprising: a battery control unit for managing a charging and a discharging of a battery; and a plurality of cell voltage sensor units (SU1-SU4), each of the cell voltage sensor units (SU1-SU4) being provided in each of cell modules (M1-M4), having a timer, for performing a voltage measurement operation of cells (C1-C12) configuring the cell modules, and for transmitting to the battery control unit, a voltage measurement result of the voltage measurement operation, wherein at least one of the plurality of cell voltage sensor units is configured to execute the voltage measurement operation at a first period, and to transmit to the battery control unit in a plurality of groups, a voltage measurement result of the voltage measurement operation at a second period shorter than the first period; wherein when a first transmission of the voltage measurement result to the battery control unit from the at least one of the plurality of cell voltage sensor units is observed, each of the other cell voltage sensor units (SU2-SU4) simultaneously executes the voltage measurement operation of the cells (C1-C12), and transmits a voltage measurement result to the battery control unit until the next time at which the first transmission from the at least one of the plurality of cell voltage sensor units to the battery control unit is observed, and when a transmission of the voltage measurement result to the battery control unit from the at least one of the plurality of cell voltage sensor units is not observed for a predetermined period of time, each of the other cell voltage sensor units (SU2-SU4) executes the voltage measurement operation of the cells (C1-C12) at a third period based on the timer, and transmits to the battery control unit in a plurality of groups, the voltage measurement result of the voltage measurement operation at a fourth period shorter than the third period, and wherein the battery control unit and the plurality of cell voltage sensor units (SU1-SU4) are connected via a CAN bus. a battery control unit for managing a charging and a discharging of a battery; and a plurality of cell voltage sensor units (SU1-SU4), each of the cell voltage sensor units (SU1-SU4) being provided in each of cell modules (M1-M4), having a timer, for performing a voltage measurement operation of cells (C1-C12) configuring the cell modules, and for transmitting to the battery control unit, a voltage measurement result of the voltage measurement operation, wherein at least one of the plurality of cell voltage sensor units is configured to execute the voltage measurement operation at a first period, and to transmit to the battery control unit in a plurality of groups, a voltage measurement result of the voltage measurement operation at a second period shorter than the first period; wherein when a first transmission of the voltage measurement result to the battery control unit from the at least one of the plurality of cell voltage sensor units is observed, each of the other cell voltage sensor units (SU2-SU4) simultaneously executes the voltage measurement operation of the cells (C1-C12), and transmits a voltage measurement result to the battery control unit until the next time at which the first transmission from the at least one of the plurality of cell voltage sensor units to the battery control unit is observed, and when a transmission of the voltage measurement result to the battery control unit from the at least one of the plurality of cell voltage sensor units is not observed for a predetermined period of time, each of the other cell voltage sensor units (SU2-SU4) executes the voltage measurement operation of the cells (C1-C12) at a third period based on the timer, and transmits to the battery control unit in a plurality of groups, the voltage measurement result of the voltage measurement operation at a fourth period shorter than the third period, and wherein the battery control unit and the plurality of cell voltage sensor units (SU1-SU4) are connected via a CAN bus.