The French scientist Nicolas Gautherot observed in 1801 that wires that had been used for electrolysis experiments would themselves provide a small amount of secondary current after the main battery had been discon. In the discharged state, both the positive and negative plates become (PbSO 4), and the loses much of its dissolved and becomes primarily water. Negative plate re. Because the electrolyte takes part in the charge-discharge reaction, this battery has one major advantage over other chemistries: it is relatively simple to determine the state of charge by merely measuring the. is a three-stage charging procedure for lead–acid batteries. A lead–acid battery's nominal voltage is 2.2 V for each cell. For a single cell, the voltage can range from 1.8 V loaded at full discharge, to 2.1.