A lead-acid battery with removable caps should be filled only with which of the following?

When maintaining a lead-acid battery with removable caps, it is essential to use distilled water for refilling purposes. Distilled water is free from impurities and minerals that can interfere with the chemical reactions occurring within the battery. The use of tap water, carbonated water, or sulfuric acid can introduce contaminants or alter the battery's chemistry, potentially leading to reduced efficiency, battery damage, or even safety hazards.

Using distilled water helps maintain the electrolyte levels in the battery while ensuring that the chemical balance remains intact. This is critical for the battery's performance, longevity, and overall health. Regularly checking and properly maintaining the water levels with distilled water is part of best practices for battery care.