Approximation function creation program, approximation function creation method, approximation function creation device, and charging rate estimation program

摘要

PROBLEM TO BE SOLVED: To provide an approximate function creation program, an approximate function creation method, an approximate function creation device, and a state-of-charge estimation program capable of accurately approximating a characteristic curve.SOLUTION: An approximate function creation device 20 includes an acquisition unit 50; a second calculation unit 52; and a creation unit 54. The acquisition unit 50 acquires data on a characteristic curve showing a correlation between an open circuit voltage of a secondary battery and a state of charge of the secondary battery. The second calculation unit 52 calculates a similarity between an approximate line and data used for approximation by the approximate line for each position of an intermediate point while moving the intermediate point in a range in which a change rate of the open circuit voltage relative to the state of charge on the characteristic curve indicated by the acquired data is equal to or smaller than a predetermined threshold, the approximate line approximating a characteristic curve of each of division ranges into which the range is divided with the intermediate point as a boundary. The creation unit 54 creates an approximate function approximating the characteristic curve using the approximate lines in the respective division ranges with the intermediate point for which the calculated similarity is highest as a boundary.