There are certain precautions to be taken when working on or near the battery: Never expose a battery to open flames or sparks which could ignite the hydrogen gas given off by the battery. Wear protective clothing and eye protection to reduce the possibility of the corrosive sulfuric acid solution inside the battery harming you. Remove all metal jewelry which could contact the positive terminal and another grounded metal source, thus causing a short circuit.
Vehicles equipped with "maintenance-free" batteries require no maintenance as the battery case is sealed and has no removable caps for adding water.
If a maintenance-type battery is installed, the caps on the top of the battery should be removed periodically to check for a low electrolyte level. This check will be more critical during the warm summer months. Some batteries can be checked without removing the caps by observing the level through the translucent case.
Remove each of the caps and add distilled water to bring the level of each cell to the split ring in the filler opening.
At the same time the battery electrolyte level is checked, the overall condition of the battery and its related components should be inspected.