PURPOSE: To improve battery so as to have long life independent of atmospheric temperature by mixing A solution obtained by mixing a small amount of sulfuric acid to water and B solution obtained by adding sodium sulfite to water, and filling the mixed solution in a container instead of electrolyte and allowing to stand several hours and charging to a specified value, then removing the mixed solution from the container to make the container liquid-free.

CONSTITUTION: A small amount of sulfuric acid is dissolved in purified water and the solution is naturally cooled. This solution is called A solution. Purified water is heated to 50∼70°C and 10∼20wt% of sodium sulfite is added to the water and heated to 75∼95°C and naturally cooled to room temperature. This solution is called B solution. Electrolyte is completely removed from a container of car battery, and mixed solution having mixing ratio of 10:1 of A solution and B solution is filled in the container. After allowing to stand several hours, the battery is charged. After completion of charging, the mixed solution is removed from the container, a liquid hole is sealed with a plug with the container liquid- free.