An electric storage device assembly comprising: a plurality of electric storage devices; and a rack on which the plurality of electric storage devices are mounted, each of the plurality of electric storage devices including: (a) a case that accommodates a battery unit provided with a first terminal portion and a second terminal portion, and that is provided with a first opening and a second opening on a first surface of the case; (b) a first terminal for external connection disposed on the first surface of the case; (c) a second terminal for external connection disposed on the first surface of the case and connected to a second terminal portion of the battery unit; (d) a conduction state switching means that is, in the case, disposed between the first terminal portion of the battery unit and the first terminal for external connection and that is opposite to the first opening, and that brings a portion between the first terminal portion of the battery unit and the first terminal for external connection into a conducting state or a non-conducting state; (e) an electronic component that is, in the case, disposed opposite to the second opening, and can be accessed from outside; and (f) a cover member having a connecting portion that is provided on an inner surface opposite to the first surface of the case and brings the conduction state switching means into a conducting state or a non-conducting state, wherein in a state where an inner surface of the cover member and the first surface of the case are opposite to each other and the connecting portion is fitted to the conduction state switching means, the cover member is attached to the first surface of the case and covers the first opening, and the second opening, the first terminal for external connection and the second terminal for external connection, a first engaging portion and a second engaging portion are provided at edge portions of the cover member, and the first engaging portion in the cover member of one electric storage device is engaged with the second engaging portion in the cover member of an electric storage device adjacent to the one electric storage device. a plurality of electric storage devices; and a rack on which the plurality of electric storage devices are mounted, each of the plurality of electric storage devices including: (a) a case that accommodates a battery unit provided with a first terminal portion and a second terminal portion, and that is provided with a first opening and a second opening on a first surface of the case; (b) a first terminal for external connection disposed on the first surface of the case; (c) a second terminal for external connection disposed on the first surface of the case and connected to a second terminal portion of the battery unit; (d) a conduction state switching means that is, in the case, disposed between the first terminal portion of the battery unit and the first terminal for external connection and that is opposite to the first opening, and that brings a portion between the first terminal portion of the battery unit and the first terminal for external connection into a conducting state or a non-conducting state; (e) an electronic component that is, in the case, disposed opposite to the second opening, and can be accessed from outside; and (f) a cover member having a connecting portion that is provided on an inner surface opposite to the first surface of the case and brings the conduction state switching means into a conducting state or a non-conducting state, (a) a case that accommodates a battery unit provided with a first terminal portion and a second terminal portion, and that is provided with a first opening and a second opening on a first surface of the case; (b) a first terminal for external connection disposed on the first surface of the case; (c) a second terminal for external connection disposed on the first surface of the case and connected to a second terminal portion of the battery unit; (d) a conduction state switching means that is, in the case, disposed between the first terminal portion of the battery unit and the first terminal for external connection and that is opposite to the first opening, and that brings a portion between the first terminal portion of the battery unit and the first terminal for external connection into a conducting state or a non-conducting state; (e) an electronic component that is, in the case, disposed opposite to the second opening, and can be accessed from outside; and (f) a cover member having a connecting portion that is provided on an inner surface opposite to the first surface of the case and brings the conduction state switching means into a conducting state or a non-conducting state, wherein in a state where an inner surface of the cover member and the first surface of the case are opposite to each other and the connecting portion is fitted to the conduction state switching means, the cover member is attached to the first surface of the case and covers the first opening, and the second opening, the first terminal for external connection and the second terminal for external connection, a first engaging portion and a second engaging portion are provided at edge portions of the cover member, and the first engaging portion in the cover member of one electric storage device is engaged with the second engaging portion in the cover member of an electric storage device adjacent to the one electric storage device.