This paper is devoted to the development of a new lead acid battery electrolyte formulation for cycling applications, especially for renewable energy markets in developing countries. These emerging markets, such as solar home systems, require lead acid batteries at very low prices and improved performances compared to automotive batteries produced locally. The new acid formulation developed is a mixture of sulphuric acid, liquid colloidal silica and other additives including phosphoric acid. The colloidal silica is used at a low concentration in order to decrease the acid strati®cation process during cycling at high depth of discharge. . | ELSEVIER Journal of Power Sources 95 2001 248-254 A new electrolyte formulation for low cost cycling lead acid batteries L. Torcheux P. Lailler CEAC Exide Europe 5 à 7 allée des pierres mayettes 92636 Genneviliers France Abstract This paper is devoted to the development of a new lead acid battery electrolyte formulation for cycling applications especially for renewable energy markets in developing countries. These emerging markets such as solar home systems require lead acid batteries at very low prices and improved performances compared to automotive batteries produced locally. The new acid formulation developed is a mixture of sulphuric acid liquid colloidal silica and other additives including phosphoric acid. The colloidal silica is used at a low concentration in order to decrease the acid stratification process during cycling at high depth of discharge. Phosphoric acid is used for the improvement of the textural evolution of the positive active material during cycling. After a description of the markets and of the additives used in the new acid formulation this paper presents the results obtained with normalised photovoltaic cycle testing on low cost automotive batteries modified by the new electrolyte formulation. It is shown that the cycling life of such batteries is much increased in the presence of the new formulation. These results are explained by the improved evolution of positive active mass softening parameters specific surface and f-PbO2 crystallite size and also by a more homogeneous sulphating process on both plates. 2001 Elsevier Science . All rights reserved. Keywords Lead acid batteries Colloidal silica Acid stratification Softening process 1. Introduction Nearly two-thirds of the world s rural inhabitants have no access to electricity and little hope of connection to national electricity grids. Stand alone renewable energies are the best solution to provide small but vital electricity quantities at low cost from sun wind water or biomass for
