A lead-acid battery consists of two lead plates separated by a liquid or gel containing sulfuric acid in water. The battery is rechargeable, with charging and discharging chemical reactions. When the battery is being used (discharged), electrons move from the negatively-charged lead plate to the positively-charged plate. The. When the battery is fully charged, the negative plate is lead, the electrolyte is concentrated sulfuric acid, and the positive plate is lead dioxide. If the battery is overcharged, electrolysis of water produces hydrogen gas. Calling sulfuric acid"battery acid" gives an indication of the acid concentration. There are, in fact, several different names for sulfuric acid that typically reflect its usage. 1. Concentration less than.