400 kJ, corresponding to the formation of 36 g of water. The net energy released per mole (207 g) of Pb(s) converted to PbSOĤ(s), is ca. The total reaction can be written as Pb(s) + PbOĢO(l) E c e l l ∘ = 2.05 V Taking advantage of the metallic conductivity of PbO The hydrogen ions screen the charged electrode from the solution which limits further reaction unless charge is allowed to flow out of the electrode. The release of two conduction electrons gives the lead electrode a negative charge.Īs electrons accumulate they create an electric field which attracts hydrogen ions and repels sulfate ions, leading to a double-layer near the surface. In the discharged state both the positive and negative plates become lead(II) sulfate ( PbSOĤ), and the electrolyte loses much of its dissolved sulfuric acid and becomes primarily water. Electrochemistry Discharge įully discharged: two identical lead sulfate plates and diluted sulfuric acid solution It was discovered early in 2011 that lead–acid batteries did in fact use some aspects of relativity to function, and to a lesser degree liquid metal and molten-salt batteries such as the Ca–Sb and Sn–Bi also use this effect. In the 1970s, the valve-regulated lead–acid battery (VRLA, or "sealed") was developed, including modern absorbed glass mat (AGM) types, allowing operation in any position.
#Agm batteries wiki portable#
Gel electrolyte batteries for any position were first used in the 1930s, and in the late 1920s, portable suitcase radio sets allowed the cell to be mounted vertically or horizontally (but not inverted) due to valve design. Using a gel electrolyte instead of a liquid allows the battery to be used in different positions without leaking. An early manufacturer (from 1886) of lead–acid batteries was Henri Tudor. In 1881, Camille Alphonse Faure invented an improved version that consisted of a lead grid lattice, into which a lead oxide paste was pressed, forming a plate. His batteries were first used to power the lights in train carriages while stopped at a station. Planté's first model consisted of two lead sheets separated by rubber strips and rolled into a spiral. In 1859, Gaston Planté's lead–acid battery was the first battery that could be recharged by passing a reverse current through it. 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. In the charged state, the chemical energy of the battery is stored in the potential difference between metallic lead at the negative side and PbO 2 on the positive side. Gel-cells and absorbed glass-mat batteries are common in these roles, collectively known as VRLA (valve-regulated lead–acid) batteries. For these roles, modified versions of the standard cell may be used to improve storage times and reduce maintenance requirements. Large-format lead–acid designs are widely used for storage in backup power supplies in cell phone towers, high-availability emergency power systems like hospitals, and stand-alone power systems. In 1999, lead–acid battery sales accounted for 40–50% of the value from batteries sold worldwide (excluding China and Russia), equivalent to a manufacturing market value of about US$15 billion. Lead-acid batteries suffer from relatively short cycle lifespan (usually less than 500 deep cycles) and overall lifespan (due to the "double sulfation" in the discharged state), as well as slow or long charging time.Īs they are inexpensive compared to newer technologies, lead–acid batteries are widely used even when surge current is not important and other designs could provide higher energy densities. These features, along with their low cost, make them attractive for use in motor vehicles to provide the high current required by starter motors. Despite this, their ability to supply high surge currents means that the cells have a relatively large power-to-weight ratio. Compared to modern rechargeable batteries, lead–acid batteries have relatively low energy density. It is the first type of rechargeable battery ever created. The lead–acid battery is a type of rechargeable battery first invented in 1859 by French physicist Gaston Planté.
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