BATTERY CHARGER OF A AIRCRAFT BATTERY
Content
1. INTRODUCTION
The purpose of this chapter is to introduce and explain the basic theory and characteristics of batteries. The batteries which are discussed and illustrated have been selected as representative of many models and types which are used in the Navy today. No attempt has been made to cover every type of battery in use, however, after completing this chapter you will have a good working knowledge of the batteries which are in general use.
First, you will learn about the building block of all batteries, the CELL. The explanation will explore the physical makeup of the cell and the methods used to combine cells to provide useful voltage, current, and power. The chemistry of the cell and how chemical action is used to convert chemical energy to electrical energy are also discussed.
Batteries are widely used as sources of direct-current electrical energy in automobiles, boats, aircraft, ships, portable electric/electronic equipment, and lighting equipment. In some instances, they are used as the only source of power; while in others, they are used as a secondary or standby power source. A battery consists of a number of cells assembled in a common container and connected together to function as a source of electrical power.
1.1 THE CELL
A cell is a device that transforms chemical energy into electrical energy. The simplest cell, known as either a galvanic or voltaic cell is shown in figure 2-1. It consists of a piece of carbon (C) and a piece of zinc (Zn) suspended in a jar that contains a solution of water (H20) and sulfuric acid (H2S0 4) called the electrolyte. The cell is the fundamental unit of the battery. A simple cell consists of two electrodes placed in a container that holds the electrolyte. In some cells the container acts as one of the electrodes and, in this case, is acted upon by the electrolyte. This will be covered in more detail later.
Figure 2-1.—Simple voltaic or galvanic cell.
1.2 ELECTRODES The electrodes are the conductors by which the current leaves or returns to the electrolyte. In the simple cell, they are carbon and zinc strips that are placed in the electrolyte; while in the dry cell (fig.2-2), they are the carbon rod in the center and zinc container in which the cell is assembled.
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Figure 2-2—Dry cell, cross-sectional view
ELECTROLYTE The electrolyte is the solution that acts upon the electrodes. The electrolyte, which provides a path for electron flow, may be a salt, an acid, or an alkaline solution. In the simple galvanic cell, the electrolyte is in a liquid form. In the dry cell, the electrolyte is a paste. CONTAINER The container which may be constructed of one of many different materials provides a means of holding (containing) the electrolyte. The container is also used to mount the electrodes. In the voltaic cell the container must be constructed of a material that will not be acted upon by the electrolyte. PRIMARY CELL A primary cell is one in which the chemical action eats away one of the electrodes, usually the negative electrode. When this happens, the electrode must be replaced or the cell must be discarded. In the galvanic-type cell, the zinc electrode and the liquid electrolyte are usually replaced when this happens. In the case of the dry cell, it is usually cheaper to buy a new cell. SECONDARY CELL A secondary cell is one in which the electrodes and the electrolyte are altered by the chemical action that takes place when the cell delivers current. These cells may be restored to
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their original condition by forcing an electric current through them in the direction opposite to that of discharge. The automobile storage battery is a common example of the secondary cell. ELECTROCHEMICAL ACTION If a load (a device that consumes electrical power) is connected externally to the electrodes of a cell, electrons will flow under the influence of a difference in potential across the electrodes from the CATHODE (negative electrode), through the external conductor to the ANODE (positive electrode). A cell is a device in which chemical energy is converted to electrical energy. This process is called ELECTROCHEMICAL action. The voltage across the electrodes depends upon the materials from which the electrodes are made and the composition of the electrolyte. The current that a cell delivers depends upon the resistance of the entire circuit, including that of the cell itself. The internal resistance of the cell depends upon the size of the electrodes, the distance between them in the electrolyte, and the resistance of the electrolyte. The larger the electrodes and the closer together they are in the electrolyte (without touching), the lower the internal resistance of the cell and the more current the cell is capable of supplying to the load. Nickel-Cadmium Cell The nickel-cadmium cell (NICAD) is far superior to the lead-acid cell. In comparison to lead- the adding of electrolyte or water. The major difference between the nickel-cadmium cell and the lead-acid cell is the material used in the cathode, anode, and electrolyte. In the nickelcadmium cell the cathode is cadmium hydroxide, the anode is nickel hydroxide, and the electrolyte is potassium hydroxide and water. The nickel-cadmium and lead-acid cells have capacities that are comparable at normal discharge rates, but at high discharge rates the nickelcadmium cell can deliver a larger amount of power. In addition the nickel-cadmium cell can: 1. Be charged in a shorter time, 2. Stay idle longer in any state of charge and keep a full charge when stored for a longer period of time, and 3. Be charged and discharged any number of times without any appreciable damage. Due to their superior capabilities, nickel-cadmium cells are being used extensively in many military applications that require a cell with a high discharge rate. A good example is in the aircraft storage battery.
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Silver-Zinc Cells The silver-zinc cell is used extensively to power emergency equipment. This type of cell is relatively expensive and can be charged and discharged fewer times than other types of cells. When compared to the lead-acid or nickel-cadmium cells, these disadvantages are overweighed by the light weight, small size, and good electrical capacity of the silver-zinc cell. The silver-zinc cell uses the same electrolyte as the nickel-cadmium cell (potassium hydroxide and water), but the anode and cathode differ from the nickel-cadmium cell. The anode is composed of silver oxide and the cathode is made of zinc. Silver-Cadmium Cell The silver-cadmium cell is a fairly recent development for use in storage batteries. The silver-cadmium cell combines some of the better features of the nickel-cadmium and silver-zinc cells. It has more than twice the shelf life of the silver-zinc cell and can be recharged many more times. The disadvantages of the silver-cadmium cell are high cost and low voltage production. The electrolyte of the silver-cadmium cell is potassium hydroxide and water as in the nickelCadmium and silver-zinc cells. The anode is silver oxide as in the silver-zinc cell and the cathode is cadmium hydroxide as in the NiCad cell. You may notice that different combinations of materials are used to form the electrolyte, cathode, and anode of different cells. These combinations provide the cells with different qualities for many varied applications.
2. NICKEL-CADMIUM BATTERY
The nickel–cadmium battery (NiCad battery or NiCad battery) is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes. The abbreviation NiCd is derived from the chemical symbols of nickel (Ni) and cadmium (Cd): the abbreviation NiCad is a registered trademark of SAFT Corporation, although this brand name is commonly used to describe all Ni–Cd batteries. Wet-cell nickel-cadmium batteries were invented in 1899. A Ni-Cd battery has a terminal voltage during discharge of around 1.2 volts which decreases little until nearly the end ofdischarge. Ni-Cd batteries are made in a wide range of sizes and capacities, from portable sealed types interchangeable with carbon-zinc dry cells, to large ventilated cells used for standby powerand motive power. Compared with other types of rechargeable cells they offer good cycle
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life and capacity, good performance at low temperatures, and work well at high discharge rates (using the cell capacity in one hour or less). However, the materials are more costly than types such as the lead acid battery, and the cells have higher self-discharge rates than some othertypes. Sealed Ni-Cd batteries require no maintenance. Sealed Ni-Cd cells were at one time widely used in portable power tools, photography equipment, flashlights, emergency lighting, and portable electronic devices. The superior capacity of the Nickel-metal hydride batteries, and more recently their lower cost, has largely supplanted their use. Further, the environmental impact of the disposal of the heavy metal cadmium has contributed considerably to the reduction in their use. Within the European Union, they can now only be supplied for replacement purposes although they can be supplied for certain specified types of new equipment such as medical devices.
Nickel–cadmium battery
From top to bottom: "Gumstick", AA, and AAA Ni–Cd batteries
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2.1 CHARACTERISTICS
The maximum discharge rate for a Ni–Cd battery varies by size. For a common AA-size cell, the maximum discharge rate is approximately 18 amps; for a D size battery the discharge rate can be as high as 35 amps. Model-aircraft or -boat builders often take much larger currents of up to a hundred amps or so from specially constructed Ni–Cd batteries, which are used to drive main motors. 5–6 minutes of model operation is easily achievable from quite small batteries, so a reasonably high powerto-weight figure is achieved, comparable to internal combustion motors, though of lesser duration. In this, however, they have been largely superseded by lithium polymer (Lipo) and lithium iron phosphate (Life) batteries, which can provide even higher energy densities. Voltage Ni–Cd cells have a nominal cell potential of 1.2 volts (V). This is lower than the 1.5 V of alkaline and zinc–carbon primary cells, and consequently they are not appropriate as a replacement in all applications. However, the 1.5 V of a primary alkaline cell refers to its initial, rather than average, voltage. Unlike alkaline and zinc–carbon primary cells, a Ni–Cd cell's terminal voltage only changes a little as it discharges. Because many electronic devices are designed to work with primary cells that may discharge to as low as 0.90 to 1.0 V per cell, the relatively steady 1.2 V of a Ni–Cd cell is enough to allow operation. Some would consider the near-constant voltage a drawback as it makes it difficult to detect when the battery charge is low. Ni–Cd batteries used to replace 9 V batteries usually only have six cells, for a terminal voltage of 7.2 volts. While most pocket radios will operate satisfactorily at this voltage, some manufacturers such as Varta made 8.4 volt batteries with seven cells for more critical applications. 12 V Ni–Cd batteries are made up of 10 cells connected in series.
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Charging
Ni–Cd batteries can be charged at several different rates, depending on how the cell was manufactured. The charge rate is measured based on the percentage of the amp-hour capacity the battery is fed as a steady current over the duration of the charge. Regardless of the charge speed, more energy must be supplied to the battery than its actual capacity, to account for energy loss during charging, with faster charges being more efficient. For example, an "overnight" charge, might consist of supplying a current equals to one tenth the amperehourrating (C/10) for 14–16 hours; that is, a 100 mAh battery takes 10mA for 14 hours, for a total of 140 mAh to charge at this rate. At the rapid-charge rate, done at 100% of the rated capacity of the battery in 1 hour (1C), the battery holds roughly 80% of the charge, so a 100 mAh battery takes 120 mAh to charge (that is, approximately 1 hour and fifteen minutes). Some specialized batteries can be charged in as little as 10–15 minutes at a 4C or 6C charge rate, but this is very uncommon. It also exponentially increases the risk of the cells overheating and venting due to an internal overpressure condition: the cell's rate of temperature rise is governed by its internal resistance and the square of the charging rate. At a 4C rate, the amount of heat generated in the cell is sixteen times higher than the heat at the 1C rate. The downside to faster charging is the higher risk of overcharging, which can damage the battery.[3] And the increased temperatures the cell has to endure (which potentially shortens its life). The safe temperature range when in use is between −20°C and 45°C. During charging, the battery temperature typically stays low, around 0°C (the charging reaction absorbs heat), but as the battery nears full charge the temperature will rise to 45–50°C. Some battery chargers detect this temperature increase to cut off charging and prevent over-charging. When not under load or charge, a Ni–Cd battery will self-discharge approximately 10% per month at 20°C, ranging up to 20% per month at higher temperatures. It is possible to perform a trickle charge at current levels just high enough to offset this discharge rate; to keep a battery fully charged. However, if the battery is going to be stored unused for a long period of time, it should be discharged down to at most 40% of capacity (some manufacturers recommend fully discharging and even short-circuiting once fully discharged[citation needed]), and stored in a cool, dry environment.
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Charging method
A Ni–Cd battery requires a charger with a slightly different voltage than for a lead–acid battery, especially if the battery has 11 or 12 cells. Also a charge termination method is needed if a fast charger is used. Often battery packs have a thermal cut-off inside that feeds back to the charger telling it to stop the charging once the battery has heated up and/or a voltage peaking sensing circuit. At room temperature during normal charge conditions the cell voltage increases from an initial 1.2 V to an end-point of about 1.45 V. The rate of rise increases markedly as the cell approaches full charge. The end-point voltage decreases slightly with increasing temperature.
Overcharging
Sealed Ni–Cd cells consist of a pressure vessel that is supposed to contain any generation of oxygen and hydrogen gases until they can recombine back to water. Such generation typically occurs during rapid charge and discharge and exceedingly at overcharge condition. If the pressure exceeds the limit of the safety valve, water in the form of gas is lost. Since the vessel is designed to contain an exact amount of electrolyte this loss will rapidly affect the capacity of the cell and its ability to receive and deliver current. To detect all conditions of overcharge demands great sophistication from the charging circuit and a cheap charger will eventually damage even the best quality cells.
Is not significantly affected by very high discharge currents. Even with discharge rates as high as 50C; a Ni–Cd battery will provide very nearly its rated capacity. By contrast, a lead acid battery will only provide approximately half its rated capacity when discharged at a relatively modest 1.5C.
Nickel–metal hydride (NiMH) batteries are the newest, and most similar, competitor to Ni– Cd batteries.
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2.2Applications
Sealed Ni–Cd cells may be used individually, or assembled into battery packs containing two or more cells. Small cells are used for portable electronics and toys, 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 favorable 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.
2.3Availability
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 1.25 and 1.35 volts, which stays relatively constant as the battery is discharged. Since an alkaline battery near fully discharged may see its voltage drop to as low as 0.9 volts, Ni–Cd cells and alkaline cells are typically interchangeable for most applications. In addition to single cells, batteries exist that contain up to 300 cells (nominally 360 volts, actual voltage under no load between 380 and 420 volts). This many cells are mostly used in automotive and heavy-duty industrial applications. For portable applications, the number of cells is normally below 18 cells (24V). Industrial-sized flooded batteries are available with capacities ranging from 12.5Ah up to several hundred Ah.
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Comparison with other batteries
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 batteries are more difficult to damage than other batteries, tolerating deep discharge for long periods. In fact, Ni–Cd batteries in long-term storage are typically stored fully discharged. This is in contrast, for example, to lithium ion batteries, which are less stable and will be permanently damaged if discharged below a minimum voltage.
Ni–Cd batteries typically last longer, in terms of number of charge/discharge cycles, than other rechargeable batteries such as lead/acid batteries.
Compared to lead–acid batteries, Ni–Cd batteries have a much higher energy density. A Ni–Cd battery is smaller and lighter than a comparable lead–acid battery. In cases where size and weight are important considerations (for example, aircraft), Ni–Cd batteries are preferred over the cheaper lead–acid batteries.
In consumer applications, Ni–Cd batteries compete directly with alkaline batteries. A Ni– Cd cell has a lower capacity than that of an equivalent alkaline cell, and costs more. However, since the alkaline batteries chemical reaction is not reversible, a reusable Ni– Cd battery has a significantly longer total lifetime. There have been attempts to create rechargeable alkaline batteries, or specialized battery chargers for charging single-use alkaline batteries, but none that have seen wide usage.
The terminal voltage of a Ni–Cd battery declines more slowly as it is discharged, compared with carbon–zinc batteries. Since alkaline batteries voltage drops significantly as the charge drops, most consumer applications are well equipped to deal with the slightly lower Ni–Cd cell voltage with no noticeable loss of performance.
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The capacity of a Ni–Cd battery Compared to Ni–Cd batteries, NiMH batteries have a higher capacity and are less toxic, and are now more cost effective. However, a Ni–Cd battery has a lower self-discharge rate (for example, 20% per month for a Ni–Cd battery, versus 30% per month for a traditional NiMH under identical conditions), although low self-discharge NiMH batteries are now available, which have substantially lower selfdischarge than either Ni–Cd or traditional NiMH batteries. This results in a preference for Ni–Cd over NiMH batteries in applications where the current draw on the battery is lower than the battery's own self-discharge rate (for example, television remote controls). In both types of cell, the self-discharge rate is highest for a full charge state and drops off somewhat for lower charge states. Finally, a similarly sized Ni–Cd battery has a slightly lower internal resistance, and thus can achieve a higher maximum discharge rate (which can be important for applications such as power tools). 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. 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.
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3. ELECTRONIC DEVICES
3.1 NPN TRANSISTOR
NPN is one of the two types of bipolar transistors, consisting of a layer of Pdoped semiconductor (the "base") between two N-doped layers. A small current entering the base is amplified to produce a large collector and emitter current. That is, when there is a positive potential difference measured from the emitter of an NPN transistor to its base (i.e., when the base is high relative to the emitter) as well as positive potential difference measured from the base to the collector, the transistor becomes active. In this "on" state, current flows between the collector and emitter of the transistor. Most of the current is carried by electrons moving from emitter to collector as minority carriers in the P-type base region. To allow for greater current and faster operation, most bipolar transistors used today are NPN because electron mobility is higher than whole mobility. A mnemonic device for the NPN transistor symbol is not pointing in, based on the arrows in the symbol and the letters in the name.[5
The symbol of an NPN BJT. The symbol is "notpointing in."
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LIMITING VALUES
In accordance with the Absolute Maximum Rating System (IEC 134).
SYMBOL PARAMETER collector-base voltage BC546 BC547 VCEO collector-emitter voltage BC546 BC547 VEBO emitter-base voltage BC546 BC547 open collector open base CONDITIONS MIN. MAX UNIT
VCBO
open emitter
_ _
80 50
V V
_ _
65 45
V V
_ _
6 6
V V
IC
collector current (DC)
_
100
mA
ICM
peak collector current
_
200
mA
IBM
peak base current
_
200
mA
Ptot
total power dissipation Tamb 25 C; note 1
_
500
mW
Tstg
storage temperature
-65
+150
C
Tj
junction temperature
_
150
C
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Tamb
operating ambient temperature
-65
+150
C
Note 1. Transistor mounted on an FR4 printed-circuit board.
CHARACTERISTICS
SYMBOL ICBO
PARAMETER collector cut-off current
CONDITIONS IE = 0; VCB= 30 V IE = 0; VCB = 30 V; Tj = 150 C
MIN.
_ _
TYP
_ _
MAX
15 5
UNIT
nA
A
IEBO
emitter cut-off current
IC = 0; VEB = 5 V
_
_
100
nA
hFE
DC current gain BC546A BC546B; BC547B BC547C
IC = 10 A; VCE = 5 V; see Figs 2, 3 and 4
90 150 270
_ _ _ 220 450 800 800 450
_ _ _ _ _ _ _
DC current gain I BC546A BC546B; BC547B BC547C BC547 BC546
IC = 2 mA; VCE = 5 V; see Figs 2, 3 and 4
110 200 420 110 110
180 290 520 _
VCEsat
collector-emitter saturation voltage
IC = 10 mA; IB = 0.5 Ma
_ _
90 200
250 600
mV mV
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IC = 10 mA; IB = 0.5 mA VBEsat base-emitter saturation voltage IC = 10 mA; IB = 0.5 mA; note 1 IC = 100 mA; IB = 5 mA; note 1 VBE base-emitter voltage IC = 2 mA; VCE = 5 V; note 2
_ _ 770 580 660 700 _ _ 700 900 _ _
mV mV
mV mV
IC = 10 mA; VCE = 5 V Cc collector capacitance Ce emitter capacitance IE = ie = 0; VCB = 10 V; f = 1 MHz IC = ic = 0; VEB = 0.5 V; f = 1 MHz fT transition frequency IC = 10mA; VCE = 5 V; f = 100 MHz F noise figure IC = 200 A; VCE = 5 V; RS = 2 k; f = 1 kHz; B = 200 Hz
_ 2 10 100 _ _ _ 11 _ _ 1.5 _
pF
pF
MHz
dB
Notes 1. VBE sat decreases by about 1.7 mV/K with increasing temperature. 2. VBE decreases by about 2 mV/K with increasing temperature.
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NPN general purpose transistors
BC546; BC547
handbook, full pagewidth
250
MBH723
hFE 200 VCE = 5 V
150
100
50
0 10 −2
10 −1
1
10
10 2
IC (mA)
103
BC546A.
Fig.2 DC Current gain; typical values.
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handbook, full pagewidth
300
MBH724
hFE
VCE = 5 V
200
100
0 10 −2
10 −1
1
10
10 2
IC (mA)
103
BC546B; BC547B.
Fig.3 DC Current gain; typical values. Philips Semiconductors Product specification
NPN general purpose transistors
BC546; BC547
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handbook, full pagewidth
600
MBH725
VCE = 5 V hFE
400
200
0 10 −2
10 −1
1
10
10 2
IC (mA)
103
BC547C.
Fig.4 DC Current gain; typical values. Philips Semiconductors Product specification
NPN general purpose transistors
PACKAGE OUTLINE
BC546; BC547
3.2 ZENER DIODE
A Zener diode is a diode which allows current to flow in the forward direction in the same manner as an ideal diode, but will also permit it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "zener knee voltage" or "zener voltage" or "avalanche point".
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The device was named after Clarence Zener, who discovered this electrical property. Many diodes described as "zener" diodes rely instead on avalanche breakdown as the mechanism. Both types are used. Common applications include providing a reference voltage for voltage regulators, or to protect other semiconductor devices from momentary voltage pulses
Zener diode
Zener diode
Type
Passive
Working principle
Zener breakdown
First production
Clarence Zener (1934)
Electronic symbol
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3.2.1FEATURES
1 . Low forward voltage 2 .High current capability 3 .Low leakage current 4 .High surge capability 5 .Low cost 3.2.2MECHANICAL DATA Case: Molded plastic use UL 94V-0 recognized Flame retardant epoxy Terminals: Axial leads, solder able per MIL-STD-202, method 208 Polarity: Color band denotes cathode Mounting Position: Any
3.3 OPERATIONAL AMPLIFIER
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An operational amplifier is a high-gain direct-coupled amplifier that is normally used in feedback connections. If the amplifier characteristics are satisfactory, the transfer function of the amplifier with feedback can often be controlled primarily by the stable and well-known values of passive feedback elements. The term operational amplifier evolved from original applications in analog computation where these circuits were used to perform various mathematical operations such as summation and integration. Because of the performance and economic advantages of available units, present applications extend far beyond the original ones, and modern operational amplifiers are used as general purpose analog data-processing elements. High-quality operational amplifiers1were available in the early 1950s. These amplifiers were generally committed to use with analog computers and were not used with the flexibility of modern units.
LM124/LM224/LM324/LM2902 Low Power Quad Operational Amplifiers 4.1General Description The LM124 series consists of four independent, high gain internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current drain is independent of the magnitude of the power supply voltage. Application areas include transducer amplifiers, DC gain blocks and all the conventional op amp circuits which now can be more easily implemented in single power supply systems. For example, the LM124 series can be directly operated off of the standard +5V power supply voltage which is used in digital systems and will easily provide the required interface electronics without requiring the additional ±15V power supplies
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.2Advantages
Eliminates need for dual supplies Four internally compensated op amps in a single package Allows directly sensing near GND and VOUT also goes to GND Compatible with all forms of logic Power drain suitable for battery operation
4.3Features
Internally frequency compensated for unity gain Large DC voltage gain 100 dB Wide bandwidth (unity gain) 1 MHz(temperature compensated) Wide power supply range: Single supply 3V to 32V or dual supplies ±1.5V to ±16V Very low supply current drain (700 μA)—essentially Independent of supply voltage Low input biasing current 45 nA (temperature compensated) Low input offset voltage 2 mV and offset current: 5 nA Input common-mode voltage range includes ground Differential input voltage range equal to the power supply voltage Large output voltage swing 0V to V+ − 1.5V
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Input Voltage Range
Input Current
00929934
00929935
Supply Current
Voltage Gain
24
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4. BATTERY CHARGER
RF80-M® Aircraft Battery Charger/Analyzer
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The NEW CHRISTIE® RF80-M® Aircraft Battery Charger/Analyzer is the latest evolution of the popular RF80 series which has been the worldwide industry standard for decades. The RF80-M is the first product of its kind to feature an advanced microcontroller with touch-screen display. The optional ABMS-10X PC Interface provides PC control, data-logging, diagnostics and expanded battery processing capabilities
Features:
7 Inch Touch Screen Display Optional PC Interface Up to 80 amps ReFLEX® Charge, 60 amps CC/CP Charge and 60 amps Discharge
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Manual Mode Program Mode Constant Current, Constant Potential and ReFLEX® charge modes Alarm signals at each end of task Programmable Alert Proven RF80-K Power Section Enhanced safety features
Benefits:
Intuitive, easy to use, and large bright display of volts, amps and time Compatible with ABMS-10X Battery Management Sys-tem for PC control, individual cell monitoring, temp sensing, data-logging, diagnostics and expanded bat-tery processing capabilities Fully compatible with all battery manufacturer’s component maintenance manuals Allows single or multiple charge/discharge tasks to be run in sequence Battery parameters may be stored and custom task sequences saved for automatic processing The only charger/analyzer offering all 3 charge modes including ReFLEX for fast charging.
5. Circuit operation:
The batteries used for aircraft starting are Nickel cadmium alkaline batteries. The main advantage of Ni-Cd batteries is that it can be used for very high current discharge for short duration. Therefore where ever storage of total energy is less critical than high discharge rate, such as aircraft starting, these batteries are preferred.
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The charging circuit must have two modes of charging, namely high current charging called boost charge till the battery attains around 90 % charge, and a constant potential float charging to maintain the battery in a charged condition by compensating for leakage.
1.45V
Voltage 1.2V
Time
Charging curve for Nicd cell
6. CONCLUSION
In the past few decades, Ni–Cd batteries have had internal resistance as low as alkaline batteries. Today, all consumer Ni–Cd batteries use the "swiss roll" or "jelly-roll" configuration. This design incorporates several layers of positive and negative material rolled into a cylindrical shape. This design reduces internal resistance as there is a greater amount of electrode in contact with the active material in each cell.
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Aircrafts usually utilize Nickel cadmium batteries for starting purpose once aircraft generator can be made on and supplies the power thereafter. Nickel cadmium batteries are high efficiency but costly batteries and need to be charged accurately.
7. DECLARATION
We here by declare that this project report entitled < BATTERY CHARGER FOR AIRCRAFT BATTERY > has been prepared by us during <date> to <date>, in partial fulfillment of the requirements for the award of Bachelor of Technology in Electrical and Electronics Engineering. We also declare that this work is a result our own effort and that it have not been submitted to any other university for the award of any Degree/Diploma.
A.ALEKHYA (09RG1A0204) M.SRILATHA (09RG1A0238) S.ANUSHA (09RG1A0256)
Place: Suraram Date:
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8. REFERENCES
1. http://www.christiecbs.com/RF80-M%20Brochure%20MAI%20%28A%29.pdf 2. S.U. Falk and A.J Salkind, Alkaline Storage Batteries, Wiley Press, New York, 1969. 3. David Linden, Handbook of Batteries (Second Edition), McGraw-Hill Inc., New York, 1994. 4. Hugh Morrow, ―Cadmium,‖ Mining Annual Review – 2000, the Mining Journal Ltd., London, UK, August 2000. 5. M. Eskra, P. Ralston, M. Klein et al., ―Nickel-Metal Hydride Replacement for VRLA and Vented NiCd Aircraft Batteries,‖ IEEE Aerospace and Electronic Systems Society Annual Battery Conference, Long Beach, CA, Jan 2001.
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The purpose of this chapter is to introduce and explain the basic theory and characteristics of batteries. The batteries which are discussed and illustrated have been selected as representative of many models and types which are used in the Navy today. No attempt has been made to cover every type of battery in use, however, after completing this chapter you will have a good working knowledge of the batteries which are in general use.
First, you will learn about the building block of all batteries, the CELL. The explanation will explore the physical makeup of the cell and the methods used to combine cells to provide useful voltage, current, and power. The chemistry of the cell and how chemical action is used to convert chemical energy to electrical energy are also discussed.
Batteries are widely used as sources of direct-current electrical energy in automobiles, boats, aircraft, ships, portable electric/electronic equipment, and lighting equipment. In some instances, they are used as the only source of power; while in others, they are used as a secondary or standby power source. A battery consists of a number of cells assembled in a common container and connected together to function as a source of electrical power.
1.1 THE CELL
A cell is a device that transforms chemical energy into electrical energy. The simplest cell, known as either a galvanic or voltaic cell is shown in figure 2-1. It consists of a piece of carbon (C) and a piece of zinc (Zn) suspended in a jar that contains a solution of water (H20) and sulfuric acid (H2S0 4) called the electrolyte. The cell is the fundamental unit of the battery. A simple cell consists of two electrodes placed in a container that holds the electrolyte. In some cells the container acts as one of the electrodes and, in this case, is acted upon by the electrolyte. This will be covered in more detail later.
Figure 2-1.—Simple voltaic or galvanic cell.
1.2 ELECTRODES The electrodes are the conductors by which the current leaves or returns to the electrolyte. In the simple cell, they are carbon and zinc strips that are placed in the electrolyte; while in the dry cell (fig.2-2), they are the carbon rod in the center and zinc container in which the cell is assembled.
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Figure 2-2—Dry cell, cross-sectional view
ELECTROLYTE The electrolyte is the solution that acts upon the electrodes. The electrolyte, which provides a path for electron flow, may be a salt, an acid, or an alkaline solution. In the simple galvanic cell, the electrolyte is in a liquid form. In the dry cell, the electrolyte is a paste. CONTAINER The container which may be constructed of one of many different materials provides a means of holding (containing) the electrolyte. The container is also used to mount the electrodes. In the voltaic cell the container must be constructed of a material that will not be acted upon by the electrolyte. PRIMARY CELL A primary cell is one in which the chemical action eats away one of the electrodes, usually the negative electrode. When this happens, the electrode must be replaced or the cell must be discarded. In the galvanic-type cell, the zinc electrode and the liquid electrolyte are usually replaced when this happens. In the case of the dry cell, it is usually cheaper to buy a new cell. SECONDARY CELL A secondary cell is one in which the electrodes and the electrolyte are altered by the chemical action that takes place when the cell delivers current. These cells may be restored to
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their original condition by forcing an electric current through them in the direction opposite to that of discharge. The automobile storage battery is a common example of the secondary cell. ELECTROCHEMICAL ACTION If a load (a device that consumes electrical power) is connected externally to the electrodes of a cell, electrons will flow under the influence of a difference in potential across the electrodes from the CATHODE (negative electrode), through the external conductor to the ANODE (positive electrode). A cell is a device in which chemical energy is converted to electrical energy. This process is called ELECTROCHEMICAL action. The voltage across the electrodes depends upon the materials from which the electrodes are made and the composition of the electrolyte. The current that a cell delivers depends upon the resistance of the entire circuit, including that of the cell itself. The internal resistance of the cell depends upon the size of the electrodes, the distance between them in the electrolyte, and the resistance of the electrolyte. The larger the electrodes and the closer together they are in the electrolyte (without touching), the lower the internal resistance of the cell and the more current the cell is capable of supplying to the load. Nickel-Cadmium Cell The nickel-cadmium cell (NICAD) is far superior to the lead-acid cell. In comparison to lead- the adding of electrolyte or water. The major difference between the nickel-cadmium cell and the lead-acid cell is the material used in the cathode, anode, and electrolyte. In the nickelcadmium cell the cathode is cadmium hydroxide, the anode is nickel hydroxide, and the electrolyte is potassium hydroxide and water. The nickel-cadmium and lead-acid cells have capacities that are comparable at normal discharge rates, but at high discharge rates the nickelcadmium cell can deliver a larger amount of power. In addition the nickel-cadmium cell can: 1. Be charged in a shorter time, 2. Stay idle longer in any state of charge and keep a full charge when stored for a longer period of time, and 3. Be charged and discharged any number of times without any appreciable damage. Due to their superior capabilities, nickel-cadmium cells are being used extensively in many military applications that require a cell with a high discharge rate. A good example is in the aircraft storage battery.
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Silver-Zinc Cells The silver-zinc cell is used extensively to power emergency equipment. This type of cell is relatively expensive and can be charged and discharged fewer times than other types of cells. When compared to the lead-acid or nickel-cadmium cells, these disadvantages are overweighed by the light weight, small size, and good electrical capacity of the silver-zinc cell. The silver-zinc cell uses the same electrolyte as the nickel-cadmium cell (potassium hydroxide and water), but the anode and cathode differ from the nickel-cadmium cell. The anode is composed of silver oxide and the cathode is made of zinc. Silver-Cadmium Cell The silver-cadmium cell is a fairly recent development for use in storage batteries. The silver-cadmium cell combines some of the better features of the nickel-cadmium and silver-zinc cells. It has more than twice the shelf life of the silver-zinc cell and can be recharged many more times. The disadvantages of the silver-cadmium cell are high cost and low voltage production. The electrolyte of the silver-cadmium cell is potassium hydroxide and water as in the nickelCadmium and silver-zinc cells. The anode is silver oxide as in the silver-zinc cell and the cathode is cadmium hydroxide as in the NiCad cell. You may notice that different combinations of materials are used to form the electrolyte, cathode, and anode of different cells. These combinations provide the cells with different qualities for many varied applications.
2. NICKEL-CADMIUM BATTERY
The nickel–cadmium battery (NiCad battery or NiCad battery) is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes. The abbreviation NiCd is derived from the chemical symbols of nickel (Ni) and cadmium (Cd): the abbreviation NiCad is a registered trademark of SAFT Corporation, although this brand name is commonly used to describe all Ni–Cd batteries. Wet-cell nickel-cadmium batteries were invented in 1899. A Ni-Cd battery has a terminal voltage during discharge of around 1.2 volts which decreases little until nearly the end ofdischarge. Ni-Cd batteries are made in a wide range of sizes and capacities, from portable sealed types interchangeable with carbon-zinc dry cells, to large ventilated cells used for standby powerand motive power. Compared with other types of rechargeable cells they offer good cycle
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life and capacity, good performance at low temperatures, and work well at high discharge rates (using the cell capacity in one hour or less). However, the materials are more costly than types such as the lead acid battery, and the cells have higher self-discharge rates than some othertypes. Sealed Ni-Cd batteries require no maintenance. Sealed Ni-Cd cells were at one time widely used in portable power tools, photography equipment, flashlights, emergency lighting, and portable electronic devices. The superior capacity of the Nickel-metal hydride batteries, and more recently their lower cost, has largely supplanted their use. Further, the environmental impact of the disposal of the heavy metal cadmium has contributed considerably to the reduction in their use. Within the European Union, they can now only be supplied for replacement purposes although they can be supplied for certain specified types of new equipment such as medical devices.
Nickel–cadmium battery
From top to bottom: "Gumstick", AA, and AAA Ni–Cd batteries
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2.1 CHARACTERISTICS
The maximum discharge rate for a Ni–Cd battery varies by size. For a common AA-size cell, the maximum discharge rate is approximately 18 amps; for a D size battery the discharge rate can be as high as 35 amps. Model-aircraft or -boat builders often take much larger currents of up to a hundred amps or so from specially constructed Ni–Cd batteries, which are used to drive main motors. 5–6 minutes of model operation is easily achievable from quite small batteries, so a reasonably high powerto-weight figure is achieved, comparable to internal combustion motors, though of lesser duration. In this, however, they have been largely superseded by lithium polymer (Lipo) and lithium iron phosphate (Life) batteries, which can provide even higher energy densities. Voltage Ni–Cd cells have a nominal cell potential of 1.2 volts (V). This is lower than the 1.5 V of alkaline and zinc–carbon primary cells, and consequently they are not appropriate as a replacement in all applications. However, the 1.5 V of a primary alkaline cell refers to its initial, rather than average, voltage. Unlike alkaline and zinc–carbon primary cells, a Ni–Cd cell's terminal voltage only changes a little as it discharges. Because many electronic devices are designed to work with primary cells that may discharge to as low as 0.90 to 1.0 V per cell, the relatively steady 1.2 V of a Ni–Cd cell is enough to allow operation. Some would consider the near-constant voltage a drawback as it makes it difficult to detect when the battery charge is low. Ni–Cd batteries used to replace 9 V batteries usually only have six cells, for a terminal voltage of 7.2 volts. While most pocket radios will operate satisfactorily at this voltage, some manufacturers such as Varta made 8.4 volt batteries with seven cells for more critical applications. 12 V Ni–Cd batteries are made up of 10 cells connected in series.
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Charging
Ni–Cd batteries can be charged at several different rates, depending on how the cell was manufactured. The charge rate is measured based on the percentage of the amp-hour capacity the battery is fed as a steady current over the duration of the charge. Regardless of the charge speed, more energy must be supplied to the battery than its actual capacity, to account for energy loss during charging, with faster charges being more efficient. For example, an "overnight" charge, might consist of supplying a current equals to one tenth the amperehourrating (C/10) for 14–16 hours; that is, a 100 mAh battery takes 10mA for 14 hours, for a total of 140 mAh to charge at this rate. At the rapid-charge rate, done at 100% of the rated capacity of the battery in 1 hour (1C), the battery holds roughly 80% of the charge, so a 100 mAh battery takes 120 mAh to charge (that is, approximately 1 hour and fifteen minutes). Some specialized batteries can be charged in as little as 10–15 minutes at a 4C or 6C charge rate, but this is very uncommon. It also exponentially increases the risk of the cells overheating and venting due to an internal overpressure condition: the cell's rate of temperature rise is governed by its internal resistance and the square of the charging rate. At a 4C rate, the amount of heat generated in the cell is sixteen times higher than the heat at the 1C rate. The downside to faster charging is the higher risk of overcharging, which can damage the battery.[3] And the increased temperatures the cell has to endure (which potentially shortens its life). The safe temperature range when in use is between −20°C and 45°C. During charging, the battery temperature typically stays low, around 0°C (the charging reaction absorbs heat), but as the battery nears full charge the temperature will rise to 45–50°C. Some battery chargers detect this temperature increase to cut off charging and prevent over-charging. When not under load or charge, a Ni–Cd battery will self-discharge approximately 10% per month at 20°C, ranging up to 20% per month at higher temperatures. It is possible to perform a trickle charge at current levels just high enough to offset this discharge rate; to keep a battery fully charged. However, if the battery is going to be stored unused for a long period of time, it should be discharged down to at most 40% of capacity (some manufacturers recommend fully discharging and even short-circuiting once fully discharged[citation needed]), and stored in a cool, dry environment.
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Charging method
A Ni–Cd battery requires a charger with a slightly different voltage than for a lead–acid battery, especially if the battery has 11 or 12 cells. Also a charge termination method is needed if a fast charger is used. Often battery packs have a thermal cut-off inside that feeds back to the charger telling it to stop the charging once the battery has heated up and/or a voltage peaking sensing circuit. At room temperature during normal charge conditions the cell voltage increases from an initial 1.2 V to an end-point of about 1.45 V. The rate of rise increases markedly as the cell approaches full charge. The end-point voltage decreases slightly with increasing temperature.
Overcharging
Sealed Ni–Cd cells consist of a pressure vessel that is supposed to contain any generation of oxygen and hydrogen gases until they can recombine back to water. Such generation typically occurs during rapid charge and discharge and exceedingly at overcharge condition. If the pressure exceeds the limit of the safety valve, water in the form of gas is lost. Since the vessel is designed to contain an exact amount of electrolyte this loss will rapidly affect the capacity of the cell and its ability to receive and deliver current. To detect all conditions of overcharge demands great sophistication from the charging circuit and a cheap charger will eventually damage even the best quality cells.
Is not significantly affected by very high discharge currents. Even with discharge rates as high as 50C; a Ni–Cd battery will provide very nearly its rated capacity. By contrast, a lead acid battery will only provide approximately half its rated capacity when discharged at a relatively modest 1.5C.
Nickel–metal hydride (NiMH) batteries are the newest, and most similar, competitor to Ni– Cd batteries.
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2.2Applications
Sealed Ni–Cd cells may be used individually, or assembled into battery packs containing two or more cells. Small cells are used for portable electronics and toys, 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 favorable 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.
2.3Availability
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 1.25 and 1.35 volts, which stays relatively constant as the battery is discharged. Since an alkaline battery near fully discharged may see its voltage drop to as low as 0.9 volts, Ni–Cd cells and alkaline cells are typically interchangeable for most applications. In addition to single cells, batteries exist that contain up to 300 cells (nominally 360 volts, actual voltage under no load between 380 and 420 volts). This many cells are mostly used in automotive and heavy-duty industrial applications. For portable applications, the number of cells is normally below 18 cells (24V). Industrial-sized flooded batteries are available with capacities ranging from 12.5Ah up to several hundred Ah.
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Comparison with other batteries
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 batteries are more difficult to damage than other batteries, tolerating deep discharge for long periods. In fact, Ni–Cd batteries in long-term storage are typically stored fully discharged. This is in contrast, for example, to lithium ion batteries, which are less stable and will be permanently damaged if discharged below a minimum voltage.
Ni–Cd batteries typically last longer, in terms of number of charge/discharge cycles, than other rechargeable batteries such as lead/acid batteries.
Compared to lead–acid batteries, Ni–Cd batteries have a much higher energy density. A Ni–Cd battery is smaller and lighter than a comparable lead–acid battery. In cases where size and weight are important considerations (for example, aircraft), Ni–Cd batteries are preferred over the cheaper lead–acid batteries.
In consumer applications, Ni–Cd batteries compete directly with alkaline batteries. A Ni– Cd cell has a lower capacity than that of an equivalent alkaline cell, and costs more. However, since the alkaline batteries chemical reaction is not reversible, a reusable Ni– Cd battery has a significantly longer total lifetime. There have been attempts to create rechargeable alkaline batteries, or specialized battery chargers for charging single-use alkaline batteries, but none that have seen wide usage.
The terminal voltage of a Ni–Cd battery declines more slowly as it is discharged, compared with carbon–zinc batteries. Since alkaline batteries voltage drops significantly as the charge drops, most consumer applications are well equipped to deal with the slightly lower Ni–Cd cell voltage with no noticeable loss of performance.
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The capacity of a Ni–Cd battery Compared to Ni–Cd batteries, NiMH batteries have a higher capacity and are less toxic, and are now more cost effective. However, a Ni–Cd battery has a lower self-discharge rate (for example, 20% per month for a Ni–Cd battery, versus 30% per month for a traditional NiMH under identical conditions), although low self-discharge NiMH batteries are now available, which have substantially lower selfdischarge than either Ni–Cd or traditional NiMH batteries. This results in a preference for Ni–Cd over NiMH batteries in applications where the current draw on the battery is lower than the battery's own self-discharge rate (for example, television remote controls). In both types of cell, the self-discharge rate is highest for a full charge state and drops off somewhat for lower charge states. Finally, a similarly sized Ni–Cd battery has a slightly lower internal resistance, and thus can achieve a higher maximum discharge rate (which can be important for applications such as power tools). 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. 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.
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3. ELECTRONIC DEVICES
3.1 NPN TRANSISTOR
NPN is one of the two types of bipolar transistors, consisting of a layer of Pdoped semiconductor (the "base") between two N-doped layers. A small current entering the base is amplified to produce a large collector and emitter current. That is, when there is a positive potential difference measured from the emitter of an NPN transistor to its base (i.e., when the base is high relative to the emitter) as well as positive potential difference measured from the base to the collector, the transistor becomes active. In this "on" state, current flows between the collector and emitter of the transistor. Most of the current is carried by electrons moving from emitter to collector as minority carriers in the P-type base region. To allow for greater current and faster operation, most bipolar transistors used today are NPN because electron mobility is higher than whole mobility. A mnemonic device for the NPN transistor symbol is not pointing in, based on the arrows in the symbol and the letters in the name.[5
The symbol of an NPN BJT. The symbol is "notpointing in."
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LIMITING VALUES
In accordance with the Absolute Maximum Rating System (IEC 134).
SYMBOL PARAMETER collector-base voltage BC546 BC547 VCEO collector-emitter voltage BC546 BC547 VEBO emitter-base voltage BC546 BC547 open collector open base CONDITIONS MIN. MAX UNIT
VCBO
open emitter
_ _
80 50
V V
_ _
65 45
V V
_ _
6 6
V V
IC
collector current (DC)
_
100
mA
ICM
peak collector current
_
200
mA
IBM
peak base current
_
200
mA
Ptot
total power dissipation Tamb 25 C; note 1
_
500
mW
Tstg
storage temperature
-65
+150
C
Tj
junction temperature
_
150
C
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Tamb
operating ambient temperature
-65
+150
C
Note 1. Transistor mounted on an FR4 printed-circuit board.
CHARACTERISTICS
SYMBOL ICBO
PARAMETER collector cut-off current
CONDITIONS IE = 0; VCB= 30 V IE = 0; VCB = 30 V; Tj = 150 C
MIN.
_ _
TYP
_ _
MAX
15 5
UNIT
nA
A
IEBO
emitter cut-off current
IC = 0; VEB = 5 V
_
_
100
nA
hFE
DC current gain BC546A BC546B; BC547B BC547C
IC = 10 A; VCE = 5 V; see Figs 2, 3 and 4
90 150 270
_ _ _ 220 450 800 800 450
_ _ _ _ _ _ _
DC current gain I BC546A BC546B; BC547B BC547C BC547 BC546
IC = 2 mA; VCE = 5 V; see Figs 2, 3 and 4
110 200 420 110 110
180 290 520 _
VCEsat
collector-emitter saturation voltage
IC = 10 mA; IB = 0.5 Ma
_ _
90 200
250 600
mV mV
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IC = 10 mA; IB = 0.5 mA VBEsat base-emitter saturation voltage IC = 10 mA; IB = 0.5 mA; note 1 IC = 100 mA; IB = 5 mA; note 1 VBE base-emitter voltage IC = 2 mA; VCE = 5 V; note 2
_ _ 770 580 660 700 _ _ 700 900 _ _
mV mV
mV mV
IC = 10 mA; VCE = 5 V Cc collector capacitance Ce emitter capacitance IE = ie = 0; VCB = 10 V; f = 1 MHz IC = ic = 0; VEB = 0.5 V; f = 1 MHz fT transition frequency IC = 10mA; VCE = 5 V; f = 100 MHz F noise figure IC = 200 A; VCE = 5 V; RS = 2 k; f = 1 kHz; B = 200 Hz
_ 2 10 100 _ _ _ 11 _ _ 1.5 _
pF
pF
MHz
dB
Notes 1. VBE sat decreases by about 1.7 mV/K with increasing temperature. 2. VBE decreases by about 2 mV/K with increasing temperature.
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NPN general purpose transistors
BC546; BC547
handbook, full pagewidth
250
MBH723
hFE 200 VCE = 5 V
150
100
50
0 10 −2
10 −1
1
10
10 2
IC (mA)
103
BC546A.
Fig.2 DC Current gain; typical values.
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handbook, full pagewidth
300
MBH724
hFE
VCE = 5 V
200
100
0 10 −2
10 −1
1
10
10 2
IC (mA)
103
BC546B; BC547B.
Fig.3 DC Current gain; typical values. Philips Semiconductors Product specification
NPN general purpose transistors
BC546; BC547
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handbook, full pagewidth
600
MBH725
VCE = 5 V hFE
400
200
0 10 −2
10 −1
1
10
10 2
IC (mA)
103
BC547C.
Fig.4 DC Current gain; typical values. Philips Semiconductors Product specification
NPN general purpose transistors
PACKAGE OUTLINE
BC546; BC547
3.2 ZENER DIODE
A Zener diode is a diode which allows current to flow in the forward direction in the same manner as an ideal diode, but will also permit it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "zener knee voltage" or "zener voltage" or "avalanche point".
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The device was named after Clarence Zener, who discovered this electrical property. Many diodes described as "zener" diodes rely instead on avalanche breakdown as the mechanism. Both types are used. Common applications include providing a reference voltage for voltage regulators, or to protect other semiconductor devices from momentary voltage pulses
Zener diode
Zener diode
Type
Passive
Working principle
Zener breakdown
First production
Clarence Zener (1934)
Electronic symbol
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3.2.1FEATURES
1 . Low forward voltage 2 .High current capability 3 .Low leakage current 4 .High surge capability 5 .Low cost 3.2.2MECHANICAL DATA Case: Molded plastic use UL 94V-0 recognized Flame retardant epoxy Terminals: Axial leads, solder able per MIL-STD-202, method 208 Polarity: Color band denotes cathode Mounting Position: Any
3.3 OPERATIONAL AMPLIFIER
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An operational amplifier is a high-gain direct-coupled amplifier that is normally used in feedback connections. If the amplifier characteristics are satisfactory, the transfer function of the amplifier with feedback can often be controlled primarily by the stable and well-known values of passive feedback elements. The term operational amplifier evolved from original applications in analog computation where these circuits were used to perform various mathematical operations such as summation and integration. Because of the performance and economic advantages of available units, present applications extend far beyond the original ones, and modern operational amplifiers are used as general purpose analog data-processing elements. High-quality operational amplifiers1were available in the early 1950s. These amplifiers were generally committed to use with analog computers and were not used with the flexibility of modern units.
LM124/LM224/LM324/LM2902 Low Power Quad Operational Amplifiers 4.1General Description The LM124 series consists of four independent, high gain internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current drain is independent of the magnitude of the power supply voltage. Application areas include transducer amplifiers, DC gain blocks and all the conventional op amp circuits which now can be more easily implemented in single power supply systems. For example, the LM124 series can be directly operated off of the standard +5V power supply voltage which is used in digital systems and will easily provide the required interface electronics without requiring the additional ±15V power supplies
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.2Advantages
Eliminates need for dual supplies Four internally compensated op amps in a single package Allows directly sensing near GND and VOUT also goes to GND Compatible with all forms of logic Power drain suitable for battery operation
4.3Features
Internally frequency compensated for unity gain Large DC voltage gain 100 dB Wide bandwidth (unity gain) 1 MHz(temperature compensated) Wide power supply range: Single supply 3V to 32V or dual supplies ±1.5V to ±16V Very low supply current drain (700 μA)—essentially Independent of supply voltage Low input biasing current 45 nA (temperature compensated) Low input offset voltage 2 mV and offset current: 5 nA Input common-mode voltage range includes ground Differential input voltage range equal to the power supply voltage Large output voltage swing 0V to V+ − 1.5V
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Input Voltage Range
Input Current
00929934
00929935
Supply Current
Voltage Gain
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4. BATTERY CHARGER
RF80-M® Aircraft Battery Charger/Analyzer
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cv `
The NEW CHRISTIE® RF80-M® Aircraft Battery Charger/Analyzer is the latest evolution of the popular RF80 series which has been the worldwide industry standard for decades. The RF80-M is the first product of its kind to feature an advanced microcontroller with touch-screen display. The optional ABMS-10X PC Interface provides PC control, data-logging, diagnostics and expanded battery processing capabilities
Features:
7 Inch Touch Screen Display Optional PC Interface Up to 80 amps ReFLEX® Charge, 60 amps CC/CP Charge and 60 amps Discharge
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Manual Mode Program Mode Constant Current, Constant Potential and ReFLEX® charge modes Alarm signals at each end of task Programmable Alert Proven RF80-K Power Section Enhanced safety features
Benefits:
Intuitive, easy to use, and large bright display of volts, amps and time Compatible with ABMS-10X Battery Management Sys-tem for PC control, individual cell monitoring, temp sensing, data-logging, diagnostics and expanded bat-tery processing capabilities Fully compatible with all battery manufacturer’s component maintenance manuals Allows single or multiple charge/discharge tasks to be run in sequence Battery parameters may be stored and custom task sequences saved for automatic processing The only charger/analyzer offering all 3 charge modes including ReFLEX for fast charging.
5. Circuit operation:
The batteries used for aircraft starting are Nickel cadmium alkaline batteries. The main advantage of Ni-Cd batteries is that it can be used for very high current discharge for short duration. Therefore where ever storage of total energy is less critical than high discharge rate, such as aircraft starting, these batteries are preferred.
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The charging circuit must have two modes of charging, namely high current charging called boost charge till the battery attains around 90 % charge, and a constant potential float charging to maintain the battery in a charged condition by compensating for leakage.
1.45V
Voltage 1.2V
Time
Charging curve for Nicd cell
6. CONCLUSION
In the past few decades, Ni–Cd batteries have had internal resistance as low as alkaline batteries. Today, all consumer Ni–Cd batteries use the "swiss roll" or "jelly-roll" configuration. This design incorporates several layers of positive and negative material rolled into a cylindrical shape. This design reduces internal resistance as there is a greater amount of electrode in contact with the active material in each cell.
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Aircrafts usually utilize Nickel cadmium batteries for starting purpose once aircraft generator can be made on and supplies the power thereafter. Nickel cadmium batteries are high efficiency but costly batteries and need to be charged accurately.
7. DECLARATION
We here by declare that this project report entitled < BATTERY CHARGER FOR AIRCRAFT BATTERY > has been prepared by us during <date> to <date>, in partial fulfillment of the requirements for the award of Bachelor of Technology in Electrical and Electronics Engineering. We also declare that this work is a result our own effort and that it have not been submitted to any other university for the award of any Degree/Diploma.
A.ALEKHYA (09RG1A0204) M.SRILATHA (09RG1A0238) S.ANUSHA (09RG1A0256)
Place: Suraram Date:
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8. REFERENCES
1. http://www.christiecbs.com/RF80-M%20Brochure%20MAI%20%28A%29.pdf 2. S.U. Falk and A.J Salkind, Alkaline Storage Batteries, Wiley Press, New York, 1969. 3. David Linden, Handbook of Batteries (Second Edition), McGraw-Hill Inc., New York, 1994. 4. Hugh Morrow, ―Cadmium,‖ Mining Annual Review – 2000, the Mining Journal Ltd., London, UK, August 2000. 5. M. Eskra, P. Ralston, M. Klein et al., ―Nickel-Metal Hydride Replacement for VRLA and Vented NiCd Aircraft Batteries,‖ IEEE Aerospace and Electronic Systems Society Annual Battery Conference, Long Beach, CA, Jan 2001.
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