Primary Cells The first primary cells were galvanic cells in which the reactants are sealed in when manufactured and ready for immediate use i.
They cannot be recharged, and when they run down, that is the chemical reactants are completely depleted, they stop working and are discarded! The copper—zinc Danielle Cell was one of the first useful batteries see 7. The common ones such as the zinc—carbon batteries are used in torches, radios, cameras, flashlights, cameras etc.
Hopefully recycling of the materials will be increasingly possible as well as being worthwhile from the point of view of conserving valuable resources and minimising environmental pollution from poisonous metals or their compounds.
The battery contains a conducting solution electrolyte paste of ammonium chloride and water, a cathode positive terminal of carbon, a depolarizer of manganese dioxide oxidizer , and an anode negative terminal of zinc reductant. How it works is described and explained below.
Dry cell zinc—carbon battery , 1. Although called a 'dry' cell, the paste must contain water, which is thickened with e. Disadvantages: Cannot be recycled, can leak weak acid electrolyte reacts with zinc , short shelf—life, unstable voltage and current as battery 'runs down' and low power. The dry cell alkaline battery, 1. Metals like cadmium or aluminium can be used as the anode, and copper, iron, lead, mercury, nickel and silver oxide can be used as cathode materials. The alkaline electrolyte does not readily react with zinc compare Zn—C cell above giving a much longer shelf—life 5 years and the current and voltage are steady handy in smoke alarms!
Disadvantages: Cannot be recycled, more expensive due to extra sealing and low power. Fuels cells are a development of primary cells but with one significant difference from their predecessors, the chemical potential energy source or 'fuel' can be continually fed in to give the cell a long active life.
The hydrogen—oxygen fuel cell equation It uses costly platinum electrodes and an acid electrolyte such as phosphoric acid, H 3 PO 4 1. But, as in electrolysis, you still get reduction at the cathode and oxidation at the anode - it can be confusing! The hydrogen—oxygen cell with an alkaline electrolyte is known as the 'alkali fuel cell' and is used in NASA's space shuttle craft.
In the charging process, the spontaneous—feasible cell reaction that produces electrical energy is reversed, so building up the chemical potential of the cell system.
Lead—acid storage battery , 2 V. The electrodes are initially hard lead—antimony alloy plates coated in a paste of lead II sulphate encased in dilute sulphuric acid.
During the first charging some of the lead II sulphate is reduced lead 0 on one of the electrodes this will acts as the — anode in discharging. Uses: Car batteries. The NiCad Cell, 1. Uses: Portable computers The lithium cell the rechargeable 'Lion battery' A popularly used commercial battery that powers many a computer!
The chemicals involved in one type are lithium metal, graphite and a lithium-cobalt oxide. The voltage and power available from a battery or cell The voltage depends primarily on the materials used in the chemical process generating the electrical energy. Since the voltage is small from an individual cell, typically 0. The power primarily depends on the amount of material and how fast the chemicals can react. For a single cell the voltage will depend on the half—cell potentials of chemicals employed, but the current flow depends on the bulk reaction rate of the chemicals.
The advantages and disadvantages of using different types of electrochemical cells Batteries - commercial electrochemical cells, have provided us with an extremely useful source of power, both in the home and industry.
Lead and Nickel Electrochemical Batteries | Wiley Online Books
They are convenient to carry around in phones, computers, torches and fitted into a variety of vehicles. You can take power to remote places without the need for expensive cabling, and rechargeable batteries via solar cells can be invaluable in this context e. The orbiting space station and spacecraft use fuels cells to provide power and collect the water produced for domestic use! You can't get a more remote location than outer space or the moon!
The Ni—Cd battery in its modern form is extremely resistant to electrical abuse anyway, so this practice has been discontinued. Vented cell wet cell , flooded cell NiCd batteries are used when large capacities and high discharge rates are required. Traditional NiCd batteries are of the sealed type, which means that charge gas is normally recombined and they release no gas unless severely overcharged or a fault develops. Unlike typical NiCd cells, which are sealed, vented cells have a vent or low pressure release valve that releases any generated oxygen and hydrogen gases when overcharged or discharged rapidly.
Since the battery is not a pressure vessel , it is safer, weighs less, and has a simpler and more economical structure. This also means the battery is not normally damaged by excessive rates of overcharge, discharge or even negative charge. They are used in aviation, rail and mass transit, backup power for telecoms, engine starting for backup turbines etc. Using vented cell NiCd batteries results in reduction in size, weight and maintenance requirements over other types of batteries.
A steel battery box contains the cells connected in series to gain the desired voltage 1. Cells are usually made of a light and durable polyamide nylon , with multiple nickel-cadmium plates welded together for each electrode inside. A separator or liner made of silicone rubber acts as an insulator and a gas barrier between the electrodes. The specific gravity of the electrolyte does not indicate if the battery is discharged or fully charged but changes mainly with evaporation of water.
The top of the cell contains a space for excess electrolyte and a pressure release vent. Large nickel-plated copper studs and thick interconnecting links assure minimum equivalent series resistance for the battery. The venting of gases means that the battery is either being discharged at a high rate or recharged at a higher than nominal rate.
This also means the electrolyte lost during venting must be periodically replaced through routine maintenance. Depending on the charge—discharge cycles and type of battery this can mean a maintenance period of anything from a few months to a year. Vented cell voltage rises rapidly at the end of charge allowing for very simple charger circuitry to be used. Typically a battery is constant current charged at 1 CA rate until all the cells have reached at least 1.
Another charge cycle follows at 0. The charge is finished with an equalizing or top-up charge, typically for not less than 4 hours at 0. The purpose of the over-charge is to expel as much if not all of the gases collected on the electrodes, hydrogen on the negative and oxygen on the positive, and some of these gases recombine to form water which in turn will raise the electrolyte level to its highest level after which it is safe to adjust the electrolyte levels. During the over-charge or top-up charge, the cell voltages will go beyond 1.
No cell should rise above 1. In an aircraft installation with a floating battery electrical system the regulator voltage is set to charge the battery at constant potential charge typically 14 or 28 V. If this voltage is set too high it will result in rapid electrolyte loss. A failed charge regulator may allow the charge voltage to rise well above this value, causing a massive overcharge with boiling over of the electrolyte.
Sealed Ni—Cd cells may be used individually, or assembled into battery packs containing two or more cells.
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Small cells are used for portable electronics and toys such as solar garden lights , often using cells manufactured in the same sizes as primary cells. When Ni—Cd batteries are substituted for primary cells, the lower terminal voltage and smaller ampere-hour capacity may reduce performance as compared to primary cells. Miniature button cells are sometimes used in photographic equipment, hand-held lamps flashlight or torch , computer-memory standby, toys, and novelties. Specialty Ni—Cd batteries are used in cordless and wireless telephones, emergency lighting, and other applications.
With a relatively low internal resistance , they can supply high surge currents. This makes them a favourable choice for remote-controlled electric model airplanes, boats, and cars, as well as cordless power tools and camera flash units. Larger flooded cells are used for aircraft starting batteries , electric vehicles , and standby power.
Advances in battery-manufacturing technologies throughout the second half of the twentieth century have made batteries increasingly cheaper to produce.
Battery-powered devices in general have increased in popularity. As of , about 1. Ni—Cd cells are available in the same sizes as alkaline batteries , from AAA through D, as well as several multi-cell sizes, including the equivalent of a 9 volt battery. A fully charged single Ni—Cd cell, under no load, carries a potential difference of between 1. Since an alkaline battery near fully discharged may see its voltage drop to as low as 0.
In addition to single cells, batteries exist that contain up to cells nominally volts, actual voltage under no load between and volts. This many cells are mostly used in automotive and heavy-duty industrial applications. Industrial-sized flooded batteries are available with capacities ranging from Recently, nickel—metal hydride and lithium-ion batteries have become commercially available and cheaper, the former type now rivaling Ni—Cd batteries in cost. Where energy density is important, Ni—Cd batteries are now at a disadvantage compared with nickel—metal hydride and lithium-ion batteries.
However, the Ni—Cd battery is still very useful in applications requiring very high discharge rates because it can endure such discharge with no damage or loss of capacity. When compared to other forms of rechargeable battery, the Ni—Cd battery has a number of distinct advantages:. The primary trade-off with Ni—Cd batteries is their higher cost and the use of cadmium. This heavy metal is an environmental hazard, and is highly toxic to all higher forms of life. They are also more costly than lead—acid batteries because nickel and cadmium cost more. One of the biggest disadvantages is that the battery exhibits a very marked negative temperature coefficient.
Lead and Nickel Electrochemical Batteries: Glaize/Lead and Nickel Electrochemical Batteries
This means that as the cell temperature rises, the internal resistance falls. This can pose considerable charging problems, particularly with the relatively simple charging systems employed for lead—acid type batteries. Whilst lead—acid batteries can be charged by simply connecting a dynamo to them, with a simple electromagnetic cut-out system for when the dynamo is stationary or an over-current occurs, the Ni—Cd battery under a similar charging scheme would exhibit thermal runaway, where the charging current would continue to rise until the over-current cut-out operated or the battery destroyed itself.
This is the principal factor that prevents its use as engine-starting batteries. Today with alternator-based charging systems with solid-state regulators, the construction of a suitable charging system would be relatively simple, but the car manufacturers are reluctant to abandon tried-and-tested technology. Ni—Cd batteries may suffer from a " memory effect " if they are discharged and recharged to the same state of charge hundreds of times. The apparent symptom is that the battery "remembers" the point in its charge cycle where recharging began and during subsequent use suffers a sudden drop in voltage at that point, as if the battery had been discharged.
The capacity of the battery is not actually reduced substantially. Some electronics designed to be powered by Ni—Cd batteries are able to withstand this reduced voltage long enough for the voltage to return to normal. However, if the device is unable to operate through this period of decreased voltage, it will be unable to get enough energy out of the battery, and for all practical purposes, the battery appears "dead" earlier than normal. There is evidence that the memory effect story originated from orbiting satellites, where they were typically charging for twelve hours out of 24 for several years.
The original paper describing the memory effect was written by GE scientists at their Battery Business Department in Gainesville, Florida, and later retracted by them, but the damage was done. It is unlikely to be a real phenomenon, but has taken on a life of its own as an urban myth. Also it is possible to lower the memory effect by discharging the battery completely about once a month. An effect with similar symptoms to the memory effect is the so-called voltage depression or lazy battery effect. This results from repeated overcharging; the symptom is that the battery appears to be fully charged but discharges quickly after only a brief period of operation.
In rare cases, much of the lost capacity can be recovered by a few deep-discharge cycles, a function often provided by automatic battery chargers. However, this process may reduce the shelf life of the battery. Many home chargers claim to be "smart chargers" which will shut down and not damage the battery, but this seems to be a common problem. In the United States , part of the battery price is a fee for its proper disposal at the end of its service lifetime. This last category has been banned effective Cadmium, being a heavy metal, can cause substantial pollution when discarded in a landfill or incinerated.
Because of this, many countries now operate recycling programs to capture and reprocess old batteries. From Wikipedia, the free encyclopedia. This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Retrieved 11 June Retrieved 18 October Business Wire.