distilled water
Car batteries are filled with sulfuric acid, not water. The battery fluids get "topped up" with distilled water if they get low.
The reason for the battery to loose water is due to the heat, in which the water will evaporate... that is why when you refill water they say to only use distilled water, as the acid is now much more concentrated. A battery that is being overcharged will also loose the fluid.
Car should be OFF. If it CAN be refilled you would remove the caps located on top of the battery. Carefully add distilled water until water level is full but not overflowing. Replace caps. Wipe off any spilled water. Do NOT get any water from battery on your clothes, skin or eyes. Do NOT smoke while refilling your battery - it could explode!
During the summer months, the battery acid can evaporate (unless you have a Maintenance Free" battery. Open the caps on your battery. You should see water directly beneath the opening. If you see the metal splines inside the battery, then you need to refill it with DISTILLED water. Don't use tap water!
in your but
My car battery and my tractor battery say the case is made of Polypropylene.
It means, that you have to refill oil and cooling water.
If you're talking about a car battery...maybe. If it is a maintenance-free battery than there is usually no way to add water to it. If it is not maintenance-free than it will usually have a way to add water, but the only type of water that should be added is pure, demineralized water.
Lead acid, wet cell.
A car battery has sulfuric (sulphuric) acid in it.
Lead acid, wet cell.
add water and charge the battery