BATTERY DIAGNOSTIC DEVICE, BATTERY DIAGNOSTIC METHOD, BATTERY DIAGNOSTIC PROGRAM, AND VEHICLE

A battery diagnostic device includes an acquisition unit that acquires a temperature and an internal resistance of a battery; a determination unit that determines a diagnostic temperature that is a temperature used for a diagnosis of the battery, based on the temperature acquired by the acquisition unit; an estimation unit that estimates the internal resistance of the battery at the diagnostic temperature based on the temperature and the internal resistance acquired by the acquisition unit and the diagnostic temperature determined by the determination unit; and a diagnosis unit that diagnoses the battery based on the internal resistance estimated by the estimation unit.