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1. Lead acid cell or lead accumulator, 2. Edison alkali cell Lead Accumulator It is a secondary cell and is the most common type of storage battery used in automobiles. It is known as lead acid cell. It was invented by French Physicist, Gaston Plante in the year 1859. Construction. It consists of a hard rubber, glass or celluloid container containing dilute sulphuric acid as the electrolyte. Each of the two electrodes consists of a set of alternate parallel mesh type perforated plates made of lead. The set of plates to be made the positive pole is filled with a paste of lead dioxide (PbO,), while the set of plates to be made the negative pole is filled with a paste of spongy lead (Pb). The positive and negative plates are kept separated and insulated from each other by porus separators made of rubber, plastic or glass fibre. This arrangement of positive and negative plates is placed inside the dilute sulphuric acid and connected to the lead terminals provided on the hard and rigid cover of the container [Fig.).
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The e.m.f. of each cell of a fully charged lead accumulator is 2.05 V and a lead accumulator of each six cells produces an e.m.f. of nerarly 12 V. The specific gravity of the electrolyte (dilute sulphuric acid) is a fully charged lead accumulator is 1.28. However, when discharged, both the e.m.f. of the cell and the specific gravity of the electrolyte fall. Whereas, e.m.f. of a cell of the accumulator should not be allowed to fall below 1.8 V, the specific gravity of the elctrolyte should not drop below 1.12."
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