Battery acid is made from a mixture of diluted sulfuric acid and distilled water. The exact ratio varies according to the model of your battery and the material of the batteries' plates.
Sulfuric acid is absorbed by the lead plates as the battery charges and discharges. The sulfate dissolves the top layer of lead plates and reduces the capacity of the battery, which can shorten its lifespan.
When a battery reaches a low level of sulfuric acid, it can be topped up with diluted sulfuric acid to restore its capacity and performance. However, adding a more concentrated form of the acid will change the chemical makeup of the battery and may even damage it.
To safely top up a battery, you'll need to remove the rubber caps that seal the individual cells of the battery and then remove the "sealing" strip that protects them from moisture. This can be done by prying up the strip with a flat screw driver or using a craft knife to cut around its edges.
You should also be prepared to wear protective clothing and safety goggles when working with this acid, which can be very toxic. You should also avoid over-charging the battery as it can produce hydrogen sulfide, a poisonous gas that has a smell similar to rotten eggs.
The safest place to buy sulfuric acid is from a reputable car parts store, like AutoZone. They carry high-quality products and offer some of the best prices in the industry.
