Energy Storage Apparatus and Failure Diagnosis Method

An energy storage apparatus includes: an external terminal ; an energy storage cell ; a current interruption device that has one end electrically connected to the external terminal and the other end electrically connected to the energy storage cell ; a discharge circuit that discharges electricity from the energy storage cell via a path that does not pass through the current interruption device ; and a failure diagnosis device . The failure diagnosis device discharges electricity from the energy storage cell using the discharge circuit , and diagnoses a failure of the current interruption device based on a change in voltage ΔV of the external terminal before and after discharging electricity.