BATTERIES






1. THEORETICAL BASES



Common use of the word, “battery” is limited to an electrochemical device that converts chemical energy into electricity, by use of a galvanic cell.
A galvanic cell is a device consisting of two electrodes (an anode and a cathode) and an electrolyte solution.
Batteries consist of one or more galvanic cells.
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2. CLASSIFICATION



There are two types of batteries:

A. PRIMARY BATTERIES (have irreversible processes):
*Voltaic Cell
*Daniel Cell
*Leclanché Cell
*Mercury batteries
*Alkaline cells

B. SECONDARY BATTERIES (can be recharged):
*Acid – lead battery
*Edison battery (Fe-Ni)
*Lithium and lithium ion





3. PRIMARY BATTERIES



A primary battery is a battery that is designed to be cycled (fully discharged) only once and then discarded.
Although primary batteries are often made from the same base materials as secondary (rechargeable) batteries, the design and manufacturing processes are not the same.
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4. SECONDARY BATTERIES



A secondary battery is commonly known as a rechargeable battery. It’s usually designed to have a lifetime of between 100 and 1000 recharge cycles, depending on the composite materials.
A single discharge cycle of a primary battery, however, will provide more current for a longer period of time than a single discharge cycle of an equivalent secondary battery.
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5. ACID VS. ALKALINE



Batteries are often classified by the type of electrolyte used in their construction.
Acid-based batteries often use sulphuric acid as the major component of the electrolyte.
The electrolyte used in mildly acidic batteries is far less corrosive than typical acid-based batteries and usually includes a variety of salts that produce the desired acidity level.
Alkaline batteries typically use sodium hydroxide or potassium hydroxide as the main component of the electrolyte.





6. WET VS. DRY



“Wet” cells refer to galvanic cells where the electrolyte is liquid in form and is allowed to flow freely within the cell casing.
“Dry” cells are cells that use a solid or powdery electrolyte. These kind of electrolytes use the ambient moisture in the air to complete the chemical process.
Cells with liquid electrolyte can be classified as “dry” if the electrolyte is immobilized by some mechanism, such as by gelling it or by holding it in place with an absorbent substance such as paper.





7. THE BATTERY OF BAGHDAD



June, 1936, workers constructing a new railway near the city of Baghdad uncovered an ancient tomb from between 190 BC to 224 AD.
Among the relics found in the tomb was a clay jar or vase, sealed with pitch at its top opening. An iron rod protruded from the center, surrounded by a cylindrical tube made of wrapped copper sheet. The height of the jar was about 15 cm, and the copper tube was about 4 cm diameter by 12 cm in length.
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Tests made on replicas, when filled with an acidic liquid such as vinegar, showed it could have produced between 1.5 and 2 volts between the iron and copper. It’s suspected that this early battery, or more than one in series, may have been used to electroplate gold onto silver artifacts.
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The german archeologist, Dr. Wilhelm Konig, identified the clay jar as a possible battery in 1938. While its 2000-year old date would make it the first documented battery invention, there may have been even earlier technology at work.
Dr. Konig also found Sumerian vases made of copper, but plated with silver, dating back to 2500 BC. No evidence of Sumerian batteries has been found to date.
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8. LUIGI GALVANI



In 1789, Luigi Galvani noticed the reaction of frog legs to voltage.
He was remarkably close to discovering the principle of the battery, but missed it because he thought the reaction was due to a property of the tissues.
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9. ALESSANDRO VOLTA



In 1800, Alessandro Volta published details of a battery.
That battery was made by piling up layers of silver, paper or cloth soaked in salt, and zinc.
Many triple layers were assembled into a tall pile, without paper or cloth between zinc and silver, until the desired voltage was reached.
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10. VOLTAIC CELL



Design :
It has cadmium amalgam and mercury sulphate poles, the electrolyte used is the cadmium sulphate.
The vertical column is formed by a succession of discs: a copper disc, a paper disc imbued in saline solution and a zinc disc. Two metal wires are attached to both ends of the column, thru them the low intensity continuous energy passes.
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The voltaic cell is used at:

1). Waters electrolysis

2). The separation of sodium (Na) and potassium (K) from their salts
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11. DANIEL CELL



In 1820, British researcher John Frederich Daniel developed an arrangement where a copper plate was located at the bottom of a wide-mouthed jar. A cast zinc piece commonly referred to as a crowfoot, because of its shape, was located at the top of the plate, hanging on the rim of the jar. Two electrolytes, or conducting liquids, were employed.
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A saturated copper sulphate solution covered the copper plate and extended halfway up the remaining distance toward the zinc piece. Then a zinc sulphate solution, a less dense liquid, was carefully poured in, to float above the copper sulphate and immerse the zinc. As an alternative to zinc sulphate, magnesium sulphate or dilute sulphuric acid was sometimes used.
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The container separated by a wall contains a copper sulphate and a zinc sulphate.
By connecting the metals using a wire, the Daniel Cell is formed.
Base chemical reactions:
(-) Zn‹s› → Zn²+ + 2e-
(-) Cu²+ + 2e- → Cu‹s›
This battery, produces 1 volt.
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The Daniel Cell was one of the first to incorporate mercury, by amalgamating it with the zinc anode to reduce corrosion when the batteries weren’t in use.
This battery, which produced about 1.1 volts, was used to power telegraphs, telephones and even to ring doorbells in homes, for over 100 years.
The applications were all stationary ones.
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12. LEAD ACID BATTERY



In 1859, Raymond Gaston Planté made a cell by rolling up two strips of lead sheet separated by pieces of flannel, and the whole assembly was immersed in dilute sulphuric acid.
By alternately charging and discharging this cell, its ability to supply current was increased.
An improved separator was needed to resist the sulphuric acid.
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Design:
1. Polyethylene case
2. Internal lead plates
3. Separators, plates of porous synthetic material
4. Electrolyte, a dilute solution of sulfuric acid
5. Lead bornes
Batteries of 12 V (for cars), have the mono block divided in 6 cells.
Each cell has 2 V, which means that a developed battery has a total of 12 V.
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Charging and discharging:
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13. LECLANCHÉ BATTERY



The first cell developed by Georges Leclanché in France was a wet cell having its electrodes immersed in a liquid. Nevertheless, it was rugged and easy to manufacture and had a good shelf life.
He later improved the battery by substituting a moist ammonium chloride paste for the liquid electrolyte and sealing the battery. The resulting battery was referred to as a dry cell, because it could be used in various positions and moved about without spilling.
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It’s the most common form of the galvanic element.
The chemical reactions are complex and can be represented:
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Its voltage is 1.5 to 1.65 volts and decreases as the battery discharges.





14. THE EDISON BATTERY



Between 1898 – 1908, Thomas Edison, developed an alkaline cell with iron as the anode material and nickel oxide as the cathode material. The electrolyte used was potassium hydroxide, the same as in modern nickel-cadmium and alkaline batteries.
The cells were well suited to industrial and railroad use. They survived being overcharged or remaining uncharged for long periods of time. Their voltage (1 to 1.35 volts) was an indication of their state of charge.
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15. THE NICKEL-CADMIUM BATTERY



In parallel with Edison's work 1893 to 1909, but independently, Jungner and Berg in Sweden developed the nickel-cadmium cell. In place of the iron used in the Edison cell, they used cadmium, with the result that it operated better at low temperatures, self-discharged itself to a lesser degree than the Edison cell and could be trickle-charged, that is, charged at a much-reduced rate.
In a different format and using the same chemistry, nickel-cadmium cells are still made and sold.
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16. THE ALKALINE-MANGANESE BATTERY



The alkaline-manganese battery, or as we know it today, the alkaline battery, was developed in 1949 by Lew Urry at the Eveready Battery Company Laboratory in Parma, Ohio.
Alkaline batteries could supply more energy at higher currents than the Leclanché batteries. Further improvements since then have increased the energy storage within a given size package.
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17. NICKEL HYDRIDE (NI-MH)



The anode of a Ni-MH cell is made of a hydrogen storage metal alloy, the cathode is made of nickel oxide, and the electrolyte is a potassium hydroxide solution.
According to one manufacturer, Ni-MH cells can last 40% longer than the same size Ni-Cd cells and will have a life-span of up to 600 cycles.
This makes them useful for high energy devices such as laptop computers, cellular phones and cam recorders.





18. NICKEL-ZINC (NI-Z)



Another alternative to using cadmium electrodes is using zinc electrodes. Although the nickel-zinc cell yields promising energy output, the cell has some unfortunate performance limitations that prevent the cell from having a useful lifetime of more than 200 or so charging cycles.
When nickel-zinc cells are recharged, the zinc does not redeposit in the same “holes” on the anode that were created during discharge. Instead, the zinc redeposit's in a somewhat random fashion, causing the electrode to become misshapen.





19. LITHIUM AND LITHIUM ION



The specific energy of some lithium-based cells can be 5 times greater than an equivalent-sized lead-acid cell and 3 times greater than alkaline batteries. Lithium cells will often have a starting voltage of 3.0 V.
Many of the inorganic components of the battery and its casing are destroyed by the lithium ions and, on contact with water, lithium will react to create hydrogen which can ignite or can create excess pressure in the cell.
Lithium primary batteries are currently being marketed for use in flash cameras and computer memory. Lithium batteries can last 3 times longer than alkaline batteries of the same size.
Button-size lithium batteries are becoming popular for use in computer memory back-up, in calculators and in watches.
In general, secondary (rechargeable) lithium-ion batteries have a good high-power performance, an excellent shelf life and a better life span than Ni-Cd batteries.





20. METAL-AIR CELLS



A very practical way to obtain high energy density in a galvanic cell is to use the oxygen in the air as a “liquid” cathode. A metal, such as zinc or aluminum, is used as the anode. The oxygen cathode is reduced in a portion of the cell that’s physically isolated from the anode. By using a gaseous cathode, more room is available for the anode and electrolyte, so the cell size can be very small while providing good energy output.
Small metal-air cells are available for applications such as hearing aids, watches and clandestine listening devices.





21. SILVER OXIDE AND MERCURY OXIDE CELLS



Silver oxide cells use silver oxide as the cathode, zinc as the anode, and potassium hydroxide as the electrolyte.
Silver oxide cells can provide higher currents for longer periods than most other specialty batteries, such as those designed from metal-air technology.
Mercury oxide cells are constructed with a zinc anode, a mercury oxide cathode, and potassium hydroxide or sodium hydroxide as the electrolyte.
Mercury creates environmental problems.





22. NICKEL-HYDROGEN CELLS



Nickel-hydrogen cells were developed for the U.S. space program. Under certain pressures and temperatures, hydrogen (which is, surprisingly, classified as an alkali metal) can be used as an active electrode opposite nickel.
Although these cells use an environmentally attractive technology, the relatively narrow range of conditions under which they can be used, combined with the unfortunate volatility of hydrogen, limits the long-range prospects of these cells for terrestrial uses.





23. OTHER BATTERIES



A Thermal Battery is a high-temperature, molten-salt primary battery. At ambient temperatures, the electrolyte is a solid, non-conducting inorganic salt. When power is required from the battery, an internal pyrotechnic heat source is ignited to melt the solid electrolyte.
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The Super Capacitor uses no chemical reaction at all. Instead, a special kind of carbon (carbon aerogel), with a large molecular surface area, is used to create a capacitor that can hold a large amount of electrostatic energy.
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The Sea Battery uses a rigid framework, containing the anode and cathode, which is immersed into the ocean to use sea water as the electrolyte.
This configuration is promising as an emergency battery for marine use.
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The Potato Battery – One vendor sells a novelty digital watch powered by a potato battery. The wearer must put a fresh slice of potato in the watch every few days.
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24. ENVIRONMENTAL CONCERNS



All battery components, when discarded, contribute to the pollution of the environment.
Some of the components, such as paperboard and carbon powder, can quickly merge into the ecosystem without noticeable impact.
Other components, such as steel, nickel and plastics, add to the volume of a landfill, since they decompose slowly.
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Of most concern are the heavy-metal battery components (cadmium, lead and mercury) which, when discarded, can be toxic to plants, animals and humans.
Several of the major battery manufacturers have taken steps to reduce the amount of toxic materials in their batteries. According to one manufacturer, it takes 6 to 10 times more energy to recycle a battery than to create the battery components from virgin materials.
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The use of rechargeable batteries is more efficient than the use of primary batteries because the batteries can be recharged and reused 25 to 1000 times before they must be discarded, reducing the volume of discarded batteries.
The most popular secondary batteries, however, contains cadmium.
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Many manufacturers, responding to customer requests and legislative demands, are designing nickel-metal hydride, lithium-ion and rechargeable-alkaline secondary batteries that contain only trace amounts of cadmium, lead or mercury.
Manufacturers have put significant efforts into improving the recycling technology to make batteries recycle more efficient and cost effective.
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