| 摘要 |
PROBLEM TO BE SOLVED: To ensure high roundness of a battery case after diameter reduction in spite of efficient and sufficient reduction of the diameter of a cylindrical battery case. SOLUTION: An electrode body 2 formed by spirally winding a positive electrode plate and a negative electrode plate through a separator is housed in a battery case 1 having the outer diameter D lager than the specified outer diameter (d). The battery case 1 is passed between at least one driving roller 24 and at least two free rollers 27, 28 by being rotated with the driving roller 24 to reduce the diameter D to the specified diameter (d) set by the diameter of an inscribed circle to three rollers 24, 27, 28. An opening of the battery case 1 whose diameter is reduced is sealed with a sealing body.
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