Calculation Device

An SBM measures a voltage of a battery, detects a voltage feature quantity, and transmits the voltage feature quantity to a BMU. The BMU measures a current of the battery, detects a current feature quantity, obtains the voltage feature quantity transmitted from the transmission unit, and calculates an impedance of the battery based on the current feature quantity and the voltage feature quantity received within a predetermined period from a time at which the current feature quantity is obtained.