DEGRADATION STATE DETERMINATION DEVICE AND DEGRADATION STATE DETERMINATION METHOD

The present invention provides a device and the like capable of determining the degradation state of a target secondary battery even if an initial measurement result of a characteristic parameter of the target secondary battery itself is not available. A present measurement value p (k) of each of plural characteristic parameters p, representing the characteristics of a secondary battery 220, is input to initial characteristic model to calculate an initial characteristic estimated value p1 (0 ← k) of a first characteristic parameter as output of the initial characteristic model. A first index value F1 (i) representing the present state of the target is calculated based on a present time series P1 (i) of the measurement value p1 (k) of the first characteristic parameter. A second index value F2 (i) representing a past state of the target is calculated on the basis of a present time series P1 (0 ← k, i) of the initial characteristic estimated value p1 (0 ← k) of the first characteristic parameter. A degradation state of the target is determined based on the first index value F1 (i) and the second index value F2 (i).