PURPOSE: To provide a sealed lead-acid battery easy to manufacture and having a stable and constant characteristic by mixing thermal expansion micro-capsules into granular powder as an electrolyte carrier.

CONSTITUTION: Thermal expansion micro-capsules are mixed into the powder having high porosity and a large specific surface area and filled between a positive electrode plate 1 and a negative electrode plate 2 and around an electrode plate group, and a sulfuric acid electrolyte necessary and sufficient for the charge/discharge of a battery is impregnated and retained. The powder is prevented from being moved during charging to generate voids between the electrode plates and reduce the battery performance. The granular powder coagulated with moisture containing silicon dioxide having a specific surface area of 150-200m2/g into the grain size of 50-200μm is used for the powder. Low-boiling point hydrocarbon is capsuled into fine spheres having the diameter of 10-30μm with the shell wall of a copolymer such as vinylidene chloride or acrylonitrile for use as the micro-capsules.