To prevent the generation of damages in battery structural parts and the periphery of a battery, even in the case where the internal pressure of the battery is suddenly raised in a lead-acid battery by forming a through- hole for communicating inside of a cell with the outside thereof at part of a lid, which is connected to a battery jar and positioned higher than the surface of the electrolyte.

A peripheral wall of a through-hole 5 is provided with an annular recessed part 5 over the circumference of the hole, and furthermore, a side surface of a sealing plate 4 is provided with an annular projecting part 4a to be paired with the recessed part 5a formed in the peripheral wall of the through hole 5, and the sealing plate 4 is fitted in a lid 1 by housing the projecting part 4 in the recessed part 5 of the peripheral wall. As the material for this sealing plate 4, the material is desirably the same as the lid, and more desirably made out of rubber. Consequently, the strength of a fitting part is lower than that of other parts, and in the case where the internal pressure of the battery is raised, the sealing plate 4 is removed before the battery jar is broken, and the inside gas is discharged, so as to prevent the generation of breakdown of a battery itself and peripheral equipment.