Check that the electrolyte level lies between the “UPPER” and the “LOWER” lines.
If the electrolyte level is below the "LOWER" line, add water until the level of electrolyte comes up to the "UPPER" level.
Remove the cell caps (A) and then carefully add distilled or purified water to bring the level of electrolyte in each cell to the "UPPER" line.
Put the cell caps back on the battery.
Charge the battery to mix the water and residual acid in the battery.
Never use the water with impurities or additives to fill the battery cells. It will reduce the life and performance of the battery.
Do not overfill the battery cells. It may result in an "overflow" of the acid electrolyte and cause corrosion on adjacent metal parts, performance deterioration and shortening the life span.
Make sure the cell caps are installed securely before charging the battery after filling the battery cells.