While servicing a battery, the technician notices it is low on fluid. What should be added to the battery?

When a technician notices that a battery is low on fluid, distilled water is the appropriate substance to add. Lead-acid batteries, which are commonly used in automobiles, require a specific electrolyte solution made primarily of sulfuric acid and water. Over time, especially if the battery has been subjected to excessive heat or is older, some of the water in the electrolyte can evaporate, leading to a low fluid level.

Adding distilled water is crucial because it is free of impurities and minerals that could interfere with the chemical processes within the battery. Impurities can cause unwanted chemical reactions, reduce battery efficiency, and lead to further corrosion.

The other options would not be suitable: baking soda could neutralize the acid and disrupt the chemical balance; hydrochloric acid is far too strong and would create dangerous reactions; and tap water can contain minerals and contaminants that might damage the battery. Using distilled water ensures that the battery maintains its intended function and lifespan.