Gaston Planté was a French physicist who invented the lead acid battery in 1859. The lead acid battery eventually became the first rechargeable electric battery marketed for commercial use.

Raymond Gaston Planté was born April 22, 1834, Orthez, France. Planté was a French physicist who produced the first electric storage battery, or accumulator, in 1859. In improved form, his invention has become the most widely used rechargeable battery. Planté followed an academic career, beginning in Paris as a lecture assistant in physics at the Conservatory of Arts and Crafts in 1854 and, six years later, rising to the post of professor of physics at the Polytechnic Association for the Development of Popular Instruction.

In 1859 Planté began experiments that resulted in construction of a battery for the storage of electrical energy. His cell used two thin lead plates separated by rubber sheets. He rolled the combination up and immersed it in a dilute sulfuric acid solution. Initial capacity was extremely limited since the positive plate had little active material available for reaction. Plante had positively charged one of his plates, making it lead oxide. The other was simply lead, which had a negative charge. His breakthrough was to create a flow of electrons from the negative plate, up out of the battery as electricity, then to feed the flow back into the battery, making the world's first rechargeable, or secondary, battery. Lead acid was reliable. But the chemistry of how it charged and discharged had seemed to defy improvement ever since.

Plante's lead-acid battery

A year later he presented a battery to the Academy of Sciences consisting of nine of the elements described above, housed in a protective box with the terminals connected in parallel. His battery could deliver remarkably large currents. Initial capacity was quite limited since the positive plate had little active material available for reaction. About 1881, Faure and others developed batteries using a paste of lead s for the positive plate active materials. This allowed much quicker formation and better plate efficiency than the solid Planté plate. Although the rudiments of the flooded lead-acid battery date back to the 1880's, there has been a continuing stream of improvements in the materials of construction and the manufacturing and formation processes. Since many of the problems with flooded lead-acid batteries involved electrolyte leakage, many attempts have been made to eliminate free acid in the battery.

 
Mechanism of the lead-acid battery operation.

The lead-acid battery uses dilute sulfuric acid for an electrolyte, lead for the anode, and lead oxide, PbO₂, for the cathode. The sulfuric acid dissociates into two hydrogen ions and a sulfate group. The sulfate group reacts with the lead anode to form lead sulfate and releases two electrons through the external circuit. This is the oxidation reaction. At the cathode, the two electrons cause a reaction to create lead sulfate and water. This is the reduction reaction. The half-cell reactions are:

At full discharge, both anode and cathode are covered with lead sulfate, and the electrolyte is mostly water. As the sulfuric acid solution is denser than water, a "densitometer", consisting of no more than a dropper with pellets of varying densities, can be used to examine the battery's charge level. Reversing the current flow reverses the reactions, recharging the battery.

Note that both electrodes dissolve into the electrolyte during the discharge reaction. When charged the reverse reactions occur, although overcharge will lead to the electrolysis of water and consequent production of (hazardous) H₂ (g) at the cathode.

The electrodes in a standard automotive battery are built as sets of interleaved plates to provide the maximum surface area for the electrochemical reaction. As the vast majority of lead-acid batteries have multiple cells in series, the battery casing contains divider walls to isolate the cells.

Each cell in a lead-acid battery provides about two volts. Lead-acid batteries usually have large capacities, though they tend to run down quickly, and can be recharged hundreds of times until their electrodes are too eroded to allow the battery to hold a charge. They have indefinite shelf lives if stored without electrolyte. Their active materials are environmentally hazardous and require recycling as a reasonable environmental safety measure, a characteristic suffered to a greater or lesser degree by most batteries, which often incorporate heavy-metal electrodes and toxic electrolytes.

The automotive lead-acid battery hasn't changed in practice for well over a century, except for changes in mechanical configuration, and the use of new packaging materials for lighter weight and greater durability. No large-capacity rechargeable battery has been developed that offers vastly greater capabilities, and no such batteries approach the lead-acid cell for its low cost.

Planté also investigated the differences between static electricity and dynamic electricity (i.e., from batteries). As part of this investigation, Planté invented a mechanical device that he called the Rheostatic Machine. The Rheostatic Machine used a bank of mica capacitors and a clever rotating commutator and a series of contacts to alternately charge a bank of capacitors in parallel (from a high voltage battery source), and then connect the capacitors in series. This arrangement multiplied the battery voltage by the number of capacitor stages to obtain very high voltages. By rapidly rotating the shaft, a series of high voltage sparks many centimeters long could rapidly be generated. This device was a mechanical predecessor of the modern day Marx generator. Using this device, Planté explored the electrical breakdown of air, the formation of Lichtenberg figures, and the behavior of thin wires when pulsed by high electric currents.

He died on May 21, 1889 in Bellevue, near Paris. In 1989, the Bulgarian Academy of Sciences established the Gaston Planté Medal, which is awarded every few years to scientists who have made significant contributions to the development of lead-acid battery technology.

French stamp with the Plante's portrait and with his rechargeable lead-acid battery.

This text has been compiled from the Plante's biography available in the Internet.

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(updated & corrected on March 22, 2007)