Thesis (M.Sc.)--Chulalongkorn University, 2008

Gelled-electrolyte used in valve-regulated lead-acid (VRLA) battery has been studied. Optimum ratios of the gelling agents, fumed silica and sulfuric acid, were chosen based on the electrical conductance. Polyacrylamide (PAM), sodium sulfate (Na2SO4), magnesium sulfate (MgSO4) and potassium sulfate (K2SO4) were examined as a possibly additive to improve the electrolyte characteristic including the battery performance. Results from these studies showed that adding PAM into the electrolyte resulted in a higher conductance, better the gel strength and shorter the gelling time while all single sulfate salt additives and mixed additives; PAM and sulfate salt, gave opposite results on conductance and gelling time. However, on the performance of the VRLA battery, the battery filled with a gelled electrolyte that had Na2SO4 as an additive provided the longest battery discharging period, the highest improvement in the battery capacity and the greatest presenting battery efficiency (98.01%).