Liquid-type lead storage battery

A lead storage battery comprising:

• a cell chamber housing an electrolyte and an electrode plate group, wherein
• the electrode plate group has a laminate containing a plurality of positive electrode plates and negative electrode plates arranged alternately and separators arranged between the positive electrode plates and the negative electrode plates,
• the positive electrode plate has a positive electrode current collector and a positive electrode mixture containing a positive electrode active material, the positive electrode active material includes lead dioxide, the positive electrode current collector has a rectangular grid substrate and a lug continuous to the grid substrate, and the positive electrode mixture is held in the grid substrate,
• the positive electrode current collector is formed of a lead alloy having a rolled structure,
• the grid substrate has frame bones forming four sides of the rectangular grid substrate and a plurality of intermediate bones connected to the frame bones and present inside the frame bones,
• the frame bones have an upper frame bone located on an upper side of the grid substrate and extending in a lateral direction, a lower frame bone located on a lower side of the grid substrate and extending in the lateral direction, and a pair of vertical frame bones extending in a vertical direction,
• the lug projects upward from a position shifted to a side close to either one of the pair of vertical frame bones from a longitudinal center of the upper frame bone,
• the plurality of intermediate bones has a plurality of vertical intermediate bones from respective positions of the upper frame bone toward a side of the lower frame bone and a plurality of lateral intermediate bones connecting the pair of vertical frame bones,
• at least one of the plurality of lateral intermediate bones is a thick lateral intermediate bone having a cross-sectional area B larger than an average value A of cross-sectional areas of the plurality of lateral intermediate bones, a cross-sectional area ratio B/A being 1.15 or more,
• a plurality of first vertical intermediate bones, which is the vertical intermediate bone extending diagonally from each position of the upper frame bone toward the side of the lower frame bone to be separated from a position directly under the lug of the lower frame bone, and a second vertical intermediate bone, which is the vertical intermediate bone arranged closest to a first vertical frame bone that is the vertical frame bone on a side far from the lug and reaching the lower frame bone, and
• an angle θL formed by a straight line indicating a direction in which the second vertical intermediate bone extends and a straight line indicating a direction in which the first vertical frame bone extends is −10° or more and 10° or less.