DIAGNOSTIC DEVICE, DIAGNOSTIC METHOD, AND COMPUTER DIAGNOSTIC PROGRAM

A diagnostic device (1) includes: an acquisition unit (2) configured to acquire data of only some battery cells of battery cells constituting a storage battery system; and a diagnostic unit (5) configured to diagnose the storage battery system (9) based on the acquired data. The data includes a voltage value and an integrated current amount value. The some battery cells include: a low-state MIN battery cell; a low-state MAX battery cell; a high-state MIN battery cell; and a high-state MAX battery cell. The diagnostic unit (5) includes at least one of: determining whether the battery cells are in a balanced state or an imbalance state; calculating an imbalance amount between capacities of the battery cells; or calculating a value related to a capacity of a battery cell.