This invention relates to an improvement on a sealed lead storage battery which comprises a case, positive and negative plates alternately disposed in a case, porous separators between the adjacent plates and electrolyte filled in the case so as to be retained at least in the porous separators.The sealed lead storage battery of the invention further comprises additional electrolyte porous retainer means disposed in an unoccupied space in the case so as to have increased amount of electrolyte. The additional electrolyte retainer means may be disposed in at least one of an upper space over the plate group, a lower space below the plate group and side spaces beside the plate group. The additional electrolyte retainer means may be of glass fine fiber mat, glass and synthetic fine fiber mat or gel. It may be integrally formed with the porous separators. Preferably, the positive and negative plates may be so porous that the electrolyte is retained in them.