Lead acid battery with gelled electrolyte formed by filtration action of absorbent separators and method for producing it

A method for producing a gelled lead acid battery that operates on the oxygen cycle, said method comprising the steps of:

• assembling a cell comprising a positive plate which has been formed and dried, at least one negative plate which has been formed and dried, and separator material between the plates, wherein the separator material constitutes an absorbent porous filtration medium and wherein there is free space between at least one of the surfaces of the separator material and at least one of the surfaces of the plates;
• inserting the cell into a case,
• introducing into the case a mixture of sulfuric acid of a given, first specific gravity, and silica including at least some silica from a never dried precipitated silica slurry, the mixture containing silica in a first, given concentration, which is below that which would cause sulfuric acid having the given specific gravity to gel, whereby sulfuric acid is absorbed into the plates and the absorbent porous filtration medium of the separator material while silica is filtered out of that sulfuric acid, thereby increasing the concentration of silica in the mixture which remains in the free space to a second concentration which causes the sulfuric acid in the mixture in the free space to gel, and sealing the case.

A method for producing a lead acid battery that operates on the oxygen cycle, said method comprising the steps of:

• assembling a cell comprising a formed and dried positive plate, a formed and dried negative plate, and, between the plates, a sheet of separator material which is an absorbent, porous filtration medium,
• inserting the cell into a case so that there is free space between the case and the adjacent edges of the plates and of the separator material,
• introducing into the case a mixture of sulfuric acid and silica including at least about 0.5 percent by weight of silica from a never dried precipitated silica slurry, the mixture containing silica in a first, given concentration, which is below that which would cause sulfuric acid having the given specific gravity to gel, whereby sulfuric acid is absorbed into the plates and the absorbent, porous filtration medium of the separator material while silica is filtered out of that sulfuric acid, thereby increasing the concentration of silica in sulfuric acid which remains in the free space to a second concentration which is higher than the first concentration and is sufficiently high to cause the sulfuric acid in the mixture in the free space to gel.