PURPOSE: To improve the self discharge performance of a lead storage battery and its restorative performance after it is left to stand in an overdischarged state by subjecting the battery to initial charging after semi-formed plates are immersed in dilute sulfuric acid.

CONSTITUTION: In constituting a sealed lead storage battery, a given amount of a positive active material paste is packed into a bass body made of an antimony-free alloy, then the thus obtained body is dried before being formed in a dilute acid of 1.100 specific gravity at a current density of 0.3A/cm2 for 40hr. At this point, the porous layers of the positive plate are filled with gas and surfaces of the active material which are in contact with the porous layers contain lower oxides comprising PbOx (X<2). After the above formation, the positive plate is released from formation wiring before being immersed in dilute sulfuric acid of 1.100 specific gravity contained in an immersion container at 40°C for 48hr. During the time when the positive plate is left to stand in the formation container for 48hr, the positive plate is degassed, PbOx and PbO2 of course become in contact with dilute sulfuric acid and these compounds are both converted into PbSO4. After the end of the above immersion, the positive plate is either dried or washed before being dried to obtain a plate which is then used to assemble a battery. Then the initial charging of the battery is performed after electrolyte consisting of a given dilute sulfuric acid is poured into the battery so as to restore both reversible PbSO4 and highly nonreversible PbSO4 to PbO2. When the active material is once converted into PbO2 completely as above, PbO4 converted from PbO2 during the time when a completed battery is left to stand is full of reversibility, thereby improving restorative performance after self discharge.