NOVELTY - The structure has a set of batteries (B1, B2) that is connected in series with bottomed cylindrical battery cases (2, 5) which function as electrode terminals on one side. Sealing plates close opening portions of the cases which function as electrode terminals on another side. A ring has a flange and is joined at a bottom portion of a case of one battery in a conductive manner. Another ring has another flange, and is jointed at an upper portion of a sealing plate (3) of an adjacent battery in a conductive manner. The rings are made of metals (1a, 1b) such as aluminum, copper or nickel.    USE - Used for connecting a set of batteries in series with bottomed cylindrical battery cases.    ADVANTAGE - The ring has the flange and is joined at the bottom portion of the case of the battery in a conductive manner, and another ring has another flange and is jointed at the upper portion of the sealing plate of the adjacent battery in a conductive manner, where rings are made of metals such as aluminum, copper or nickel, thus eliminating the need for a separator or gasket made of a synthetic resin whose heat resistance is relatively low compared with a metal at the time of welding, and hence improving welding output to obtain firm welding between the batteries. The welding output is improved to obtain firm welding between the batteries, thus strengthening mechanical strength at a welding portion and effectively allowing the connection structure to be used with mobility and vibration, and hence expecting radiation effect between the batteries to inhibit the temperature rise which is caused by lowering the battery characteristics, and avoiding the loss of money for defect in the structure.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method of manufacturing unit cells.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic cross-sectional view of a connecting state of a connection structure between unit cells.    Batteries (B1, B2)    Metals (1a, 1b)    Bottomed cylindrical battery cases (2, 5)    Sealing plate (3)    Gasket (4)    Rubber valve (6)    Fixing frame (18)    Cylindrical portions (21, 22)