Secondary battery diagnostic method, secondary battery diagnostic program, and secondary battery diagnostic device

A secondary battery diagnostic method comprising:

• estimating, on the basis of data obtained by measuring load characteristics of a secondary battery to be diagnosed, characteristic parameters of the secondary battery to be diagnosed at a time of diagnosis by using a predetermined model equation, the characteristic parameters including an electrolyte diffusion coefficient Dn of the secondary battery to be diagnosed at the time of diagnosis;
• estimating, on the basis of input data, a threshold value Dth of the electrolyte diffusion coefficient of the secondary battery to be diagnosed by using a learned model, the input data being data including some of the characteristic parameters at the time of diagnosis;
• and
• obtaining a difference ΔD between the threshold value Dth and the electrolyte diffusion coefficient Dn at the time of diagnosis, wherein
• for each of a plurality of secondary batteries for learning, the following process is performed:
• determining characteristic parameters of the secondary battery for learning;
• obtaining, on the basis of the model equation and the characteristic parameters of the secondary battery for learning, a discharge capacity when an electrolyte diffusion coefficient of the secondary battery for learning is changed, and obtaining a relationship between the electrolyte diffusion coefficient and the discharge capacity of the secondary battery for learning;
• and
• determining, on the basis of the relationship between the electrolyte diffusion coefficient and the discharge capacity of the secondary battery for learning, a threshold value of the electrolyte diffusion coefficient of the secondary battery for learning, and
• the learned model is generated by machine learning utilizing teacher data obtained by using, as input data, data including some of the characteristic parameters of the secondary batteries for learning and, as output data, the threshold values of the electrolyte diffusion coefficients of the secondary batteries determined.