PURPOSE: To prevent short-circuit of the captioned battery by covering a positive plate with an opposite U-shaped separator and covering it with an opposite U- shaped negative plate comprising an expanded grid.

CONSTITUTION: A positive plate 2 is covered with an opposite U-shaped separator 3 and the separator 3 is covered with an opposite U-shaped negative electrode 1 comprising an expanded grid to form an electrode group. A shelf 4 and a reinforcement bridge 6 of the negative plate 1 is separated from the upper part of the positive plate by the separator 3. In a small sealed lead-acid battery constructed with this electrode group, short-circuit between the shelf 4 or the reinforcement bridge 6 and the positive plate 2 is prevented even if the positive plate is expanded.