ESTIMATION METHOD, ESTIMATION SYSTEM, ESTIMATION COMPUTER PROGRAM, AND NON-TRANSITORY COMPUTER-READABLE RECORDING MEDIUM

An estimation method includes: performing, for each different degree of degradation, regression analysis between a first value and a second value, wherein the first value is related to one or more reference feature points on a differential curve of a charging-discharging curve indicating a voltage value (V) with respect to integrated current amount (Q) of a reference storage battery (R), and the second value is at least one of a capacity value of the reference storage battery (R) and an internal resistance value of the reference storage battery (R); and estimating at least one of a capacity value of a target storage battery (11) and an internal resistance value of the target storage battery (11), based on a result of the regression analysis and a third value related to one or more target feature points on a differential curve of a charging-discharging curve of the target storage battery (11).