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Batteries: More Than You Want To Know

http://gizmodo.com/5952938/everything-you-need-to-know-about-batteries






Nobody thinks about batteries—until they've run out of juice, of course. But this humble and surprisingly ancient technology has done far more for human civilization than most people realize.
In fact, the modern world as we know it wouldn't exist were it not for batteries and the unique, utterly essential ability to store electrical energy that they provide. Without batteries, there is no such thing as mobile. Phones, computers, bio-medical devices, even the lowly flashlight: every single electronic device on Earth would have to compete for open an wall socket just to turn on.
So let's think about batteries for a minute. Or better yet, explain everything you could possibly want to know about what they are, where they come from, and—most importantly—how to get the most out of them.

A Brief History of Batteries

Baghdad Battery: Bringing Bling to Mesopotamia
It's like a scene from Raiders of the Lost Ark. In 1936, a number of small, oddly-anointed terracotta pots were discovered in in the ruins of a village near the modern-day town of Khuyut Rabbou'a on the outskirts of Baghdad, Iraq. Clearly from antiquity, their ages dated to either the Parthian era (248 BC - 226 AD) or Sassanid (224-640 AD), but without an obvious use, the curious jars were donated to the National Museum of Iraq. There they sat on a shelf for two years until the museum's German director, Wilhelm König, rediscovered them in the museum's archives around 1938. Upon König's return to the fatherland in 1940 due to illness, he published a speculative paper that the mysterious vessels may have been a lost precursor of the galvanic cell, one perhaps used to electroplate thin layers of gold onto the plated silver pieces he kept finding during excavations.
Each clay jar measured roughly 5.5 inches tall and was outfitted with a small copper tube (constructed from a rolled copper sheet) surrounding an oxidized iron rod but separated by an asphalt plug. Were the vessel to be filled with an acidic or alkaline liquid, say, lemon juice, grape juice, or vinegar, many experts believe that it could well have generated a small but appreciable current (on the range of .8 to 2 volts if replica devices are any indication). Granted, this amount of voltage generally isn't powerful enough for the uses König imagined as the Mythbusters proved. Anthropologists now believe those pieces were fire-plated using mercury and some speculate that the Baghdad Battery could instead have served as a miracle device in ancient religious or healing ceremonies.
"The batteries have always attracted interest as curios," Dr Paul Craddock, a metallurgy expert of the ancient Near East from the British Museum, told the BBC. "They are a one-off. As far as we know, nobody else has found anything like these. They are odd things; they are one of life's enigmas."
Galvanic Cells: Darth Vader to the Modern Battery's Luke
Frog's legs are funny things. Not just good eatins, they exhibit a tendency to flail when exposed to an electrical charge. At least, that's what Luigi Galvani discovered in 1771 as a professor at the University of Bologna. As the legend goes, he was in the process of skinning a frog pinned via copper hooks to a table where he had just previously conducted various static electric experiments. Galvani's assistant picked up a metal scalpel from the table (which, unbeknownst to either man, carried a static electric charge) and accidentally touched an exposed sciatic nerve. With a small spark, the leg twitched and Galvani glimpsed that electric charge could actually transported by ions, not through fluids or the atmosphere as earlier theories posited.
He didn't actually figure that out, mind you, he incorrectly assumed that this "animal electricity" originated in the tissue itself, conducted by an "electrical fluid." This perverse notion would pervade for nearly thirty years, Galvani's discovery that two metals, when connected via a salt bridge and simultaneously touched to a nerve would cause such a reaction paved the way for the modern electric battery and the advent of the Galvanic cell.
Voltaic Pile: Were Yurtle the Turtle a Galvanic Cell

Galvani's misconceptions about the origin of electricity in living beings lasted for the rest of his life, believing that "animal electricity" was borne from a muscle within the hip. Alessandro Giuseppe Antonio Volta, professor of experimental physics at the University of Pavia, was one of the first of Galvani's contemporaries to recreate his famous frog experiment and originally held the same views on animal electricity's hip-based origins. But what Volta realized, and Galvani did not, was that the frog leg was both capable of conducting and detecting electricity.
To prove this point, Volta built a a device he dubbed an "artificial electrical organ." Created by alternatively stacking silver and zinc discs separated by brine-soaked cloth, this arrangement created a circuit and would conduct a charge when connected by a wire. As Volta wrote to Sir Joseph Banks, the president of the Royal Society of London, on the 20th of March 1800:
... In this manner I continue coupling a plate of silver with one of zinc, and always in the same order, that is to say, the silver below and the zinc above it, or vice versa, according as I have begun, and interpose between each of those couples a moistened disk. I continue to form, of several of this stories, a column as high as possible without any danger of its falling.
While he had been attempting to mimic a perceived biological function, Volta had actually invented the Voltaic Pile, world's first electric battery. It also led him to discover Volta's Law of the electrochemical series—the electromagnetic force of a galvanic cell is dependent on the electrical potential difference of the electrodes. This is why stacking nothing but copper or silver discs will not generate a current.
Galvanic cells rely on a pair of half-cells, each with a differing electrode dipped in electrolytic solution to generate a RedOx reaction and, in turn, an electrical charge. Unlike an electrolytic cell that requires electrical input to get started, the galvanic cell's RedOx reaction is spontaneous. That is, it occurs without any outside impetus. As such, galvanic cells were originally found use powering telegraph lines and improved designs are now often found in batteries, pH meters, and fuel cells.
The Voltaic pile didn't just lead to batteries. It's invention directly led to numerous other major scientific discoveries. William Nicholson and his half-brother Anthony Carlisle built their own voltaic pile and passed the current through a trough of water, thereby discovering electrolysis as the H20 decomposed into its constituent elements. Humphry Davy in the UK used his own voltaic pile to demonstrate that Volta's Law was based on a chemical reaction, not just the electrode's difference in potential, as well as further Nicholson's and Carlisle's electrolysis work. William Hyde Wollaston proved that voltaic and static electricity were one and the same. And just two years after its creation, Vasily Petrov was using them to study electrical arcs.
While the Voltaic pile was a pioneering effort, it wasn't exactly practical—short circuits from leaking electrolyte were as common as hydrogen bubbles forming on the leads. These shortcomings spawned a raft of design improvements and re-imaginings. To solve the short circuiting issue, William Cruickshank, professor of chemistry at the Royal Military Academy, Woolwich, simply laid the pile on its side in an insulated rectangular box with pairs of zinc and copper plates welded together. These plates were evenly spaced throughout the box and created self-contained cells for the electrolyte mixture of dilute sulfuric acid.
The spillage issue was also addressed in 1812 with the invention of the Zamboni pile—also known as the Duluc Dry Pile—invented by Giuseppe Zamboni. Constructed from thousands of sheets of alternating silver and zinc foil, the Zamboni pile's manganese oxide electrolyte was held in place with honey and the entire affair was crammed into a long glass jar and insulated with pitch. This construction gives Zamboni piles potential outputs in the Kilowatt range, which makes modern versions very handy in a variety of military and scientific applications.
Perhaps the most momentous improvement upon Volta's original design came in 1866. Georges Leclanché found that a cell employing a zinc anode and manganese dioxide/carbon cathode dipped in a bath of ammonium chloride would produce 1.4 volts, a far cry from the original pile's .4V and equivalent to a modern alkaline battery. With a stronger electrical oomph, the dry Leclanché cell quickly found use powering early telephone systems. The only problem was that the chemical reaction that powered the phone also caused resistance to increase, causing the battery to quickly run down. The process would reverse when load was removed from the cell but you'd have to keep your conversations short. More importantly, Leclanché's cell laid the groundwork for the modern dry cell batteries that now power a majority of our gadgets.


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