The lead–acid battery is a type of rechargeable battery first invented in 1859 by French physicist Gaston Planté. It is the first type of rechargeable battery ever created. Compared to modern rechargeable batteries, lead–acid batteries have relatively low energy density. Despite this, they are able to supply high surge. 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 disconnected. 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 of the electrolyte; the specific. PlatesThe lead–acid cell can be demonstrated using sheet lead plates for the two electrodes. However, such a construction produces only around one ampere for roughly postcard-sized plates, and for only a few minutes. Starting batteriesLead–acid batteries designed for starting automotive engines are not designed for deep discharge. They have a large number of thin plates designed for maximum surface area, and therefore maximum current output,. DischargeIn 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 reaction. 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 2.10 V in an open circuit at full charge. Most of the world's lead–acid batteries are (SLI) batteries, with an estimated 320 million units shipped in 1999. In 1992 about 3 million tons of lead were used in the manufacture of batteries. Wet cell stand-by.