Abnormality detection method, abnormality detection device, energy storage apparatus, and computer program

An abnormality detection method detects abnormality of an assembled battery including energy storage devices by an abnormality detection device. Each energy storage device contains, as a positive active material, lithium iron phosphate and lithium transition metal oxide that allows insertion and extraction reaction of a lithium ion in a potential range higher than that of the lithium iron phosphate. A ratio of an amount of charge based on a total amount of the lithium transition metal oxide to an amount of charge based on a total amount of the positive active material in a charge-discharge range, in which the energy storage device is used, is 5% or more. The abnormality detection device acquires voltage of each of the energy storage devices near a charge end point in the charge-discharge range where the energy storage device is used and detects abnormality in the assembled battery using the acquired voltage of the energy storage devices.