DETERIORATION DIAGNOSIS APPARATUS OF ASSEMBLED BATTERY AND DETERIORATION DIAGNOSIS METHOD OF ASSEMBLED BATTERY

A deterioration diagnosis apparatus of an assembled battery includes at least one processor. The at least one processor executes discharging of each of a plurality of cells included in the assembled battery, measures a voltage of each of the cells during the discharging, ends the discharging at a predetermined discharging end timing, and estimates a deterioration degree of the assembled battery using voltage data indicating a transition of a voltage of at least one of the cells from a discharging start voltage to a predetermined discharging end voltage. When the voltage of at least one of the cells reaches the discharging end voltage, the at least one processor decides the discharging end timing using the voltage data of the cell of which the voltage reaches the discharging end voltage.