Battery monitor system

A battery monitor system for monitoring a battery state of a plurality of battery cells, the battery monitor system comprising:

• a reference signal generation unit that generates an alternating-current orthogonal reference signal;
• an excitation signal generation unit that processes an in-phase signal of the orthogonal reference signal to generate an excitation signal;
• a current generation unit that generates an excitation current based on the excitation signal and energizes each battery cell;
• a current measurement unit that measures the excitation current generated by the current generation unit;
• a voltage measurement unit that measures a voltage of each battery cell;
• an impedance measurement unit that measures an alternating-current impedance of each battery cell based on the excitation current measured by the current measurement unit and the voltage measured by the voltage measurement unit;
• a noise measurement unit that measures a noise superimposed on each battery cell as a noise voltage based on the voltage measured by the voltage measurement unit and estimates a noise current;
• and
• a control unit that controls a measurement of the alternating-current impedance and a measurement of the noise voltage, wherein:
• the control unit selects one or more battery cells that are not a measurement target of the alternating-current impedance from among the plurality of battery cells;
• and
• the noise measurement unit measures the noise voltage near a measurement frequency equal to a frequency of the orthogonal reference signal while the current generation unit connected to selected one or more battery cells is not operated and only the voltage measurement unit is operated.