battery basics

BATTERY BASICS: A primer for battery technology

Battery Basics A primer for battery technology

Prepared by and for the Power Sources Team of CECOM’s Logistics and Readiness Center

This primer is intended to provide a basic understanding of battery technology for those with little or no background in chemistry. The descriptive style used herein depends in part on analogies in order to provide an intuitive understanding of some concepts rather than explain them in scientific terms. It is designed for use by the CECOM LRC Power Sources Team. It is provided here for informational purposes only and cannot be used for any other purpose without written consent. POC: Patrick Lyman, QA Specialist, CECOM LRC Power Sources Team, telephone (732) 532-8824 or DSN 992-8824, and e-mail address [email protected]

Table of Contents

Battery Basics....................................................................................................1

PART 1: The Fundamentals........................................................................3

Classification......................................................................................................................................3 Primary Batteries ..............................................................................................................................3 Rechargeable Batteries ................................................................................................................4

The Atom .............................................................. 4 (Basic chemistry as it applies to batteries)

Battery Definition........................................................................................................................6

The Cell ...........................................................................7 (Basic building block for all batteries) Anode....................................................................................................................... 7 (Reducing Agent) Cathode................................................................................................................................. 7 (Oxidizer) Electrolyte ........................................................................................................... 7 (Ionic Conductor) Separator.............................................................................................7 (Insulator, Ionic Transport)

Electrochemical Action.................................... 8 (Oxidation-Reduction, or REDOX) Discharge .................................................................................................................................................8 Charge.........................................................................................................................................................8

Determining Cell Voltage .................................. 9 (Standard Reduction Potentials)

Electricity Basics 10 (Wiring Diagrams and Ohm's Law)

Building Batteries With Cells....................................................................................11 Voltage.....................................................................................................................................................11 Current......................................................................................................................................................12

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mailto:[email protected]


Power.........................................................................................................................................................13 Energy (or Capacity) ...................................................................................................................13 Safety.........................................................................................................................................................14

PART 2: CECOM Batteries ......................................................................14

General Information .... 14 (Anode, cathode, electrolyte & cell voltages of battery chemistries) General Characteristics of CECOM Batteries . 15 (Power, Energy, Environmental Limits) Aircraft Batteries .................................................................... 17 (Vented Nickel Cadmium)

Type/Construction/Chemistry/Common Problems ..........................................17 Maintenance ..........................19 (Difference between AVUM & AVIM; charging methods)

Commo Batteries.......20 (Batteries that power communications electronics devices) Lithium Sulfur Dioxide.............................................................................................................20 Lithium Manganese Dioxide................................................................................................22 Zinc Air ...................................................................................................................................................23 Sealed Nickel Cadmium...........................................................................................................24 Sealed Nickel Metal Hydride...............................................................................................25 Lithium Ion...........................................................................................................................................25

Appendix A..................................................................................................... (Periodic Table)

Appendix B........................................................................................... 29 (Glossary of Terms)

Appendix C..........................................................................................................31 (References)

NAVIGATIONAL NOTE: Terms appearing in blue bold text are listed in Appendix B, Glossary of Terms. They are linked to the Glossary for your reference. Words appearing in green text are associated to a footnote.

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PART 1: The Fundamentals

But there is an important difference. Classification Before we go into the technical details of how batteries work, it’s important to note that there are two common types of batteries that account for all the batteries that CECOM manages: Primary and Rechargeable. The term “primary” was first used to describe this type based on the fact that the materials inside the battery were the prime source of the electric power it delivered, while the “secondary” (or rechargeable) batteries had to receive a charge before they could deliver any power. Although we seldom use the term “secondary” any more, the term “primary” has survived. The military officially prefers the term “non-rechargeable”, which won’t appear again in this text. The main difference between them is not the electrochemistry of the cells so much as it is the physical structure required to allow for safe restoration of the original materials after discharge (charging). (top)

Primary Batteries

Primary batteries are capable of one-time use: use it until it’s depleted and then dispose of it. The most common primary batteries in the world today are alkaline D, C, AA, AAA and 9-volt batteries. These batteries use zinc as the anode and manganese dioxide as the cathode with potassium hydroxide as the electrolyte – the “alkaline” part of the battery.

NOTE: The term “alkaline”, or base, refers to caustic solutions that are the opposite of acids. Acids and bases are graded on the same scale for their relative strength: the pH scale. Setting pure water at 7, considered the neutral point on the scale, acids are rated lower and bases, higher. Potassium hydroxide, the “alkaline” in alkaline batteries, is rated at about 12. Sulfuric acid, used in lead-acid batteries, is rated at about 2.

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Most of the primary batteries managed by CECOM use lithium as the anode and either

sulfur dioxide or manganese dioxide as the cathode. (top) Rechargeable Batteries

Rechargeable batteries are constructed in such a way as to allow for a restoration of the original electrode materials by applying a voltage from an external source. The oldest rechargeable battery still in use is the familiar lead-acid battery. These batteries use lead as the anode, lead dioxide as the cathode, and sulfuric acid as the electrolyte. Both electrodes are converted to lead sulfate in discharge; charging converts them back to their original materials. This is a rare case of the electrolyte actually taking part in the discharge process. This is the reason why it has been possible to determine the state of charge of a lead-acid battery by checking the specific gravity of the electrolyte. Specific gravity is a measure of a liquid’s density. Water is said to have a specific gravity of 1.0. If a liquid is more dense than water, its specific gravity will be greater than one. If it’s less dense than water, the number will be less than one. Lead-acid batteries have a specific gravity of 1.28 when fully charged and 1.12 when fully discharged.

The rechargeable batteries managed by CECOM come in three chemistries: nickel-

cadmium, nickel-metal hydride, and lithium ion. The nickel-cadmium batteries can have either vented or sealed cells. The former type is used in aircraft; the latter type is used for communications-electronics equipment. (top) The Atom All materials found in nature are built with the basic building block of the atom. The atom consists of a nucleus of positively charged particles called protons along with neutral particles called neutrons. This nucleus is orbited by negatively charged particles called electrons. The quantity of protons and electrons should be equal in order for the material to be stable. The electrons are organized into shells around the nucleus, each shell limited in the amount of electrons it can hold and each successive shell further away from the nucleus. The outermost shell of any atom is referred to as the valence shell; it is this valence shell that determines the properties of the atom.

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electron

neutron

proton

Figure 1: An atom, showing 6 electrons orbiting a nucleus. Atoms with a full valence shell are inert gases. Every other element acts as if it wants to be like the inert gases – in other words, exist with a full outer shell. Atoms with one or two electrons in their valence shell give them up easily, leaving behind a full shell (except for hydrogen). Atoms with a nearly full valence shell can easily take electrons away from other atoms. The former elements make good anode materials; the latter make good cathode materials. This will be explained in more detail later. Appendix A contains a periodic table of the elements for reference. NOTE: This appendix had to be removed from the document due to formatting problems. To view, click on the link; when done, press the BACK button of your browser to return here. (top)

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Valence ShellNucleus: Protons & Neutrons

1

2

3

4

Electron Shell Number

1

2 Electrons, MAX

2

8 Electrons, MAX

318 Electrons, MAX

432 Electrons, MAX

Valence Shell:The outermost electron shell. This shell defines the properties of the element.

Materials with few electrons in the valence shell make good ANODES; materials lacking just one or two electrons to complete the valence shell make good CATHODES

Figure 2: Diagram of Electron Shells (or Energy Levels) showing maximum electrons for each. Materials that do not have an equal number of protons and electrons are called ions. Those with missing electrons are called cations (positive ions); those with additional electrons are called anions (negative ions). Ions seek out oppositely charged ions and react with them to form stable compounds. (top) Battery Definition A battery is a device that converts chemical energy into electric energy. This is done by the transfer of electrons from one material to another through an electric circuit. This transfer results in the oxidation of a reducing agent (the anode) and the reduction of an oxidizer (the cathode), a process called oxidation-reduction or REDOX. The term “oxidation” means that a material is losing electrons; the term “reduction” means that the material is gaining electrons. (top)

NOTE: An Example of REDOX that is not electrochemical in nature is the rusting of metal. The transfer of electrons in this case occurs directly and only heat is involved. Another example is the formation of sodium chloride, where a sodium atom loses an electron and the chlorine atom gains one. Sodium chloride is the chemical name for table salt.

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How can it be called “reduction” when it’s gaining an electron? The answer is in the observation of the phenomenon long before anyone knew that electrons existed. They were able to tell that a material that gained electrons had a negative electric charge, while those that lost electrons had a positive charge. Not knowing that the exchange of electrons was involved and believing that positive was more than negative, materials with the negative charge were thought to have been reduced. The Cell The basic building block of all batteries. It consists of two electrodes (an anode and a cathode), electrolyte, a separator between the anode and cathode, and some type of cell container. (top) Anode

The negative electrode1. As stated above, it is the reducing electrode, also known as the fuel electrode. The anode gives up its electrons to the external circuit and is oxidized in the process. Anodes are made from materials with very few electrons in their valence shell. Almost all anodes are made from either metals or compounds that include metals. (top) Cathode

The positive electrode, also known as the oxidizing electrode. This is designed to accept electrons from the external circuit and is reduced in the process. Cathodes are made from materials that have nearly full valence shells. Cathodes are typically made from compounds that include oxygen, chlorine, or both. (top) Electrolyte

The ionic conductor. While the electrons are passing through the external circuit, the electrode materials inside the cell are changing into ions. In order to sustain the flow of electrons, the newly formed ions have to pass between the electrodes through the electrolyte. Electrolytes are typically either acids or bases (alkaline), although newer technologies tend to use organic solvent and salt solutions. Acids, bases, and salt solutions all make good ionic conductors. (top) Separator

The separator provides insulation between the anode and cathode while allowing ionic transport between the electrodes. (top)

1 Defining the anode as the negative electrode holds true for voltaic cells, the type used to build batteries. There is another type of cell, the electrolytic cell, in which the positive/negative definitions are reversed, since the action of electrolytic cells is viewed from within the electrolyte, not from outside the cell.

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Electrochemical Action When the anode is connected to the cathode through an external circuit, the cell undergoes discharge. REDOX occurs: the anode material loses electrons (oxidation) and the cathode material gains electrons (reduction). For rechargeable batteries, applying a voltage in the reverse direction (from discharge) institutes REDOX in the opposite direction. In a battery, REDOX occurs only at the surface of the electrodes. A reaction involving the entire mass of both a reducing agent and an oxidizer would be either a fire or an explosion. (top) Discharge

The flow of electrons from the anode to the cathode through an electric circuit. Ions form on both electrodes and flow through the electrolyte to react with one another to form new stable compounds. In most practical batteries, the discharge product is formed on the surface of the cathode. (top)

El e c t r o n f l o w

D ISC H AR G E C H AR G E

(-) (-)

E lectrochem ica l Action

El e c t r o n f l o w

(+) (+ )

Figure 3: Discharge and charge processes in a basic cell.

Charge

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The flow of electrons from the cathode to the anode induced by an external power source. The discharge product separates out into ions that travel through the electrolyte. The original electrode materials return to their starting points. NOTE: Curious about memory? (top) Determining Cell Voltage Cell voltage is dependent in part on the electrode potential of the materials chosen, typically referred to as the “standard reduction potential”. A table of common electrode potentials appears below:

ANODE MATERIALS CATHODE MATERIALS Material Potential Material Potential Zinc -0.76 (in acid electrolyte) Chlorine 1.36 Zinc -1.25 (in base electrolyte) Oxygen 1.23 Lithium -3.01 Sulfur Dioxide 0.0 Lead -0.13 Lead Dioxide 1.69 Cadmium Hydroxide -0.81 Nickel (as NiOOH) 0.49

Table 1: Electrode potentials for some common battery chemistries The theoretical voltage of a given cell is the difference in potential between the two materials. This can be determined using a number line:

Figure 4: Number line showing theoretical cell voltages for two common battery chemistries

The potential is an “absolute” value, determined by the total value between the two points. The lithium sulfur dioxide potential is obvious, since sulfur dioxide has a zero-volt potential. The absolute value of the difference between them is 3.01 volts. The nickel-cadmium potential isn’t so obvious. The absolute difference between –0.81 volts and +0.49 volts is 1.30 volts, the total difference between them, or rather, the total distance between the two points on the number line. Common cell voltages are provided in Table 2 below. (top)

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Electricity Basics Batteries are used as a portable source of electric power. Before we go into detail about how batteries are built, we’ll first have to cover some basics regarding electric circuits. The most basic electric circuit involving a battery is the flashlight. A battery is used to light the flashlight bulb. It is connected to the bulb through a switch. Figure 5 below uses common symbols for electricity to provide a visual map of this circuit. (top)

(-)

(+)Battery

Switch

FlashlightBulb

Connections,or Wire

The position of the switch in thisdiagram means that it is OPEN; ifthe switch touched the contact on theother side, it would be CLOSED

This is the symbol for an electrochemical cell; this battery has only one cell.

Figure 5: Basic Wiring Diagram (flashlight)

The wiring diagram above includes a single-cell battery, a switch, and a flashlight bulb. The switch is displayed in the “OPEN” position. When open, the battery is disconnected from the bulb. When the switch is closed, the battery is connected to the bulb and electric current begins to flow, lighting the bulb. The three electric properties of this circuit are voltage, current, and resistance. Current is measured in amperes which are indicated by “A”; resistance is measured in ohms which are indicated by the omega symbol, “Ω”. Voltage is measured in volts which are indicated with a “V”. The battery provides the voltage. The bulb, switch, wires and all connections provide the resistance. The amount of current in the circuit is determined by the voltage of the battery and the resistance offered by the circuit. In other words, the value of current is dependent on the

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voltage applied and the resistance of the circuit components. The relationships of these three properties can be displayed as:

Ohm’s Law

E

I R

Where:E represents Voltage;I represents Current;R represents Resistance

E = IR

E/I = R

E/R = I

Voltage is the productOf current & resistance

voltage divided by current is Resistance

voltage divided by resistance is Current

Figure 6: Relationship of voltage, current & resistance (Ohm’s Law)

In our example above (Figure 5), the battery has 1.5 volts. Bulbs don’t come with a resistance rating; they’re usually rated in watts, and flashlight bulbs typically have low wattage ratings. Wattage is a measure of power, which is the product of voltage and current (more on the topic of power later). Since the bulb offers more resistance than any other component of the circuit, the wattage rating of the bulb and the voltage of the battery will determine how much current flows in this circuit. Using a bulb with a 1 watt rating in this circuit would result in 1 W ÷ 1.5V = 0.67A (1 watt divided by 1.5 volts equals 0.67 amperes). Using ohms law (Figure 6 above), we see that this 1 watt bulb provides the resistance equivalent in ohms of 1.5V ÷ 0.67 A = 2.25 Ω (1.5 volts divided by 0.67 amperes equals 2.25 ohms). As we’ll see later on, we’d have to be careful in our selection of a battery for this circuit to make sure it can provide that much current (see the description of power density in Part 2). (top) Building Batteries With Cells Voltage

Voltage is a difference in potential. One volt is said to exist when the difference in potential between two points is equal to one coulomb of electrons. A coulomb is a quantity of 6.28 X 1018 electrons.

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The voltage of a battery can be set to any desired value in two ways: First, by selection of the cell materials, particularly the electrode materials; and second, by the number of cells in series. In the example below in Figure 7, the Li/SO2 potential is set to about 3 volts. By placing three cells in series, we obtain 9 volts. (top)

L O A D

(-)(+ )

L O A D

(-)

(+ )

S E R IE S – C e lls a re co nn ected in se riesT o increase vo lta ge

P A R A L L E L – C ells a re co n nected in p ara lle l to incre ase curren t

9 V olts, 2 A m ps

3 V o lts , 6 A m psF or th is exam ple, cells are lith ium su lfu r d ioxide D cells

Figure 7: Series and parallel arrangements of cells

Current

Current, the flow of electrons, is measured in amperes, as discussed above under the topic of Electricity Basics. One ampere is said to flow when one coulomb of electrons pass through a point in one second. The ampere capability of a battery can be determined in several ways: First, by the materials of the cell; second, by the physical structure of the cell; third, by the size of the cell, and lastly, by the number of cells in parallel. The first two ways to establish the current handling capability of a battery discussed above are methods for setting cell impedance. Impedance is a type of resistance; it is the total of all the factors in an electric circuit that oppose the flow of current. The higher the cell impedance, the lower the current capability of the cell. Choosing materials that can easily react with each other through an electric circuit is one way to limit cell impedance. Another way is by increasing the surface area of the electrodes. The most common methods for increasing electrode surface area are to spirally wind cells that fit into cylindrical cans (Figure 13), or to connect parallel plates inside a rectangular cell (Figure 9).

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Cell size also helps to determine the current capability of a cell. Larger cells can provide more current than smaller cells with the same chemistry, partly due to the larger surface area of the electrodes. In other words, size does matter. To see how parallel arrangements of cells work, let’s go back to the example given for battery voltage in Figure 7. Placing three Li/SO2 cells in series will give us a battery with 9 volts. This combination will safely produce a maximum of 2 amperes constant current, as in the BA-5600A/U and BA-5599A/U. If a device needed 3 volts and up to 6 amperes, we could connect the three cells in parallel. (top)

Power Parallel arrangements of cells do not magically produce more power. In an electric

circuit, power, measured in watts, is the product of both voltage and current. Batteries are needed to provide power, not just voltage. From the example in Figure 7 above, the same three cells produce 18 watts of power in either configuration:

9V X 2A = 3V X 6A = 18W. An example of how a battery can have a variable voltage and current capability in a

finished battery is the dual section arrangement in the BA-5590B/U and BA-5557A/U batteries, as well as the rechargeable counterparts, BB-390B/U and BB-557A/U. Here, the external connection on the using equipment can connect the two sections to produce either 30 volts with 2 amperes maximum capability, or 15 volts with 4 amperes maximum capability in the BA-5590B/U (0.65 amperes and 1.3 amperes respectively for the BA-5557A/U which has smaller cells than the BA-5590B/U). The rechargeable versions have higher current handling capability but provide less energy. How the using device connects the separate sections depends on its operating voltage. No matter how a using device connects to these batteries, they provide the same amount of power. (top)

Energy (or Capacity)

The capacity of a given battery chemistry is typically measured in terms of energy density: the ratio of the energy available from a cell or battery to its volume. The values used are usually the watt-hours (energy) per liter (volume), expressed as Wh/L. Sometimes you will find cubic centimeters (cm3) used as the measure of volume. Another measure used is the watt-hours per unit of weight, usually kilograms (Wh/kg).

NOTE: An example of the difference between power and energy can be found in automobiles: How FAST a car can go relates to power; how FAR it can go on a tank of gas relates to energy.

Factors affecting energy density are: the theoretical energy of the cells (the electrodes and electrolyte used, size and shape of the electrodes); the amount of “dead” material in the battery (separators, binders, cans, air space, jackets etc); and the size of the battery. “Size” relates to the amount of active materials available. (top)

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Safety

The discussion of voltage and current above leads to issues of safety. Limiting cell impedance by choosing materials that easily react with one another could lead to violent reactions, sometimes as soon as when the cells are assembled. One of the main methods that chemists and chemical engineers use to avoid this is by determining what reactions are favored when the various cell materials exist within the same container. A full discussion of determining favored reactions is beyond the scope of this primer. A simple example can be found in ships at sea. The water of oceans and seas isn’t pure water; it contains materials that cause it to act like both an oxidizer and an electrolyte. This could easily oxidize the steel hull of a ship (rust). To prevent this, ships at sea typically have a cathodic protector, with the most basic type being a large piece of zinc. The oxidation reaction to the zinc is said to be favored, thereby providing oxidation protection to the other metal parts of the ship. (top)

PART 2: CECOM Batteries General Information The Power Sources Team of CECOM’s LRC manages two basic categories of batteries by application: communications-electronics (commo) batteries, and aircraft batteries. The latter consists of vented nickel cadmium batteries like the BB-664/A and BB-432B/A used in Army helicopters. The former types can be primary or rechargeable. In fact, we offer primary and rechargeable alternatives in the same (or similar) configurations. Table 2 below is provided for your reference. To help with analogies used earlier, the examples of alkaline and lead-acid batteries are included. The main points to note from this table are the cell voltages. In the previous section the use of cells in series to provide a desired voltage was discussed. In the example in Figure 7, lithium sulfur dioxide cells were used to demonstrate how three cells could be connected in series to produce 9 volts (3 cells x 3 volts per cell = 9 volts). If we wanted to use alkaline cells instead, we would require six cells (6 cells x 1.5 volts = 9 volts). Using nickel cadmium cells to get 9 volts creates a common problem: multiples of cell voltages don’t equate. 1.2 volts times 6 cells is only 7.2 volts; using 7 cells would give us 8.4 volts; using 8 cells would give us 9.6 volts. The solution to this problem relates to the topic of power discussed in the previous section. Nickel cadmium batteries can provide higher currents than their alkaline counterparts, so 7.2 volts is enough to power the same devices that need 9 volts from alkaline batteries. (top)

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Cell Voltage Chemistry Anode (-) Cathode (+) Electrolyte Nominal End Primary Batteries Alkaline Zinc Manganese Dioxide Potassium Hydroxide 1.5 0.9

Lithium Sulfur Dioxide Lithium Sulfur Dioxide Organic Solvent, Salt Solution 3 2

Lithium Manganese Dioxide Lithium Manganese DioxideOrganic Solvent, Salt Solution 3.3 2

Zinc-Air Zinc Oxygen Potassium Hydroxide 1.5 0.9 Rechargeable Batteries Lead Acid Lead Lead Dioxide Sulfuric Acid 2 1.75 Vented Nickel Cadmium Cadmium Nickel Hydroxide Potassium Hydroxide 1.2 1 Sealed Nickel Cadmium Cadmium Nickel Hydroxide Potassium Hydroxide 1.2 1 Nickel Metal Hydride Metal Hydride Nickel Hydroxide Potassium Hydroxide 1.2 1

Lithium Ion Carbon Lithiated Cobalt Dioxide Organic Solvents 4 2.5

Table 2: Chemical Composition and Voltage of CECOM Battery Chemistries

How can Lithium Ion batteries have a carbon anode? This is an example of a technically correct but useless fact. When lithium ion cells are assembled, there is no active material in the anode. After assembly, the cells are subject to a charge, which transfers the lithium in the lithiated cobalt dioxide over to the anode. General Characteristics of CECOM Batteries Table 3 below summarizes the essential characteristics of the chemistries used in CECOM batteries, with alkaline and lead-acid battery data included for reference. Zinc-Air batteries are also included as we plan on procuring some soon. The next three columns report power density and average energy density numbers for typical battery configurations. Energy density equates to how much fuel you can pack into a battery; power density equates to how fast you can use it up. Power density is described by adjectives while energy density can be expressed in numbers. The first, Wh/L, tells you how much energy (or fuel) you have by unit of volume, or space. The second, Wh/kg, is the measure of energy to the weight required. Highlighted in italics are the Wh/L for lithium manganese dioxide batteries and the Wh/kg for lithium sulfur dioxide. If a Project Manager was weighing options on which chemistry to use in a certain application, these numbers would tell him that the lithium manganese dioxide batteries would provide more energy based on the amount of space that can be spared, while lithium sulfur dioxide batteries provide more energy by weight. The next four columns deal with temperature extremes. The “best” numbers in each column are highlighted (print in bold & italics). Lithium sulfur dioxide batteries can work in the widest possible range of temperatures. Low temperature storage limits are posted here only to warn of possible irreversible damage due to freezing the electrolyte, more of a problem with large, flooded cell batteries (like lead-acid automotive batteries or nickel cadmium aircraft batteries). Damage to the other types due to freezing is less likely.

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Temperature Extremes by volume by weight Storage Operation

Chemistry Power

Density Wh/L Wh/kg Low High Low High Self-

DischargeCycle Life

Primary Batteries

% per yr at 70F

Alkaline Moderate 330 125 -40F 130F -4F 130F 4% 1 Lithium Sulfur Dioxide

Moderate to high 415 260 -65F 160F -60F 160F 2% 1

Lithium Manganese Dioxide

Moderate to high 550 230 -40F 140F -4F 130F 2% 1

Zinc-Air Low 1050 340 -40F 140F -4F 130F 6% 1 Rechargeable Batteries

% per mon at 70F

Lead Acid High 70 35 -60F 130F -40F 130F 20-30% 200 Vented Nickel Cadmium

High 90 37 -65F 140F -40F 122F 10% 500

Sealed Nickel Cadmium

Moderate to high 80-105 30-35 -65F 113F -40F 113F 15-20% 300

Nickel Metal Hydride

Moderate to high 175 50 113F -4F 122F 20% 300

Lithium Ion Moderate 200 90 130F -4F 130F 5-10% 500

Energy Density

Table 3: Characteristics of CECOM Battery Chemistries

Self-Discharge is the amount of energy lost while a battery waits to be used. The primary batteries win out in this category by a large margin. But before you write off the rechargeables, remember that the energy they lose can be replaced by recharging. The last column is the reason why the Army has a policy for maximum use of rechargeables. They’re heavier, they store less energy per unit volume or unit weight, they don’t work as well as primaries in extreme environments and they lose significant amounts of energy waiting to be used, but they can be used over and over again. The cycle life values here are the standard published numbers for commercial batteries. The military expects fewer: only 150 for lead-acid and 220 for the others. When compared overall, Zinc-Air wins in the energy density categories, but it has limits: It can’t produce equivalent power densities in sizes equal to the lithium batteries and can’t work when wet (or whenever the oxygen supply is cut off). Lithium sulfur dioxide can take environmental extremes better than any other. But this chemistry has its draw-backs too: the cell contains a pressured toxic gas which can vent. Lithium manganese dioxide batteries have better energy density by volume without the pressurized gas, but don’t handle temperature extremes as well. The data in Table 3 relates to commercially available cells (except for lithium sulfur dioxide, used in mostly military applications). The information is also several years old. Every chemical system listed, other than lithium sulfur dioxide and sealed nickel cadmium, has gotten better. This is the result of research and development work generated by the dissatisfaction with these two chemistries from the military and from the commercial market. (top)

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Aircraft Batteries

Figure 8: CECOM Aircraft Nickel Cadmium Batteries Reference: TM 11-6140-203-23, 15 JUL 94, with Change 2, 1 FEB 96. Aircraft batteries have to deliver a great deal of energy in a relatively short time, and do it in a wide range of temperatures. The type of battery best suited to this purpose is the vented, sintered-plate nickel cadmium battery. (top) Type/Construction/Chemistry/Common Problems

“Vented” is a term that could easily get confused with the “venting” of sealed-cell batteries. Used here, it means that the cells are built with a vent, designed to release excess pressure inside the cell and then seal up again to prevent accidental spills of the electrolyte. The vent operates every time the air pressure inside the cell exceeds a set limit.

“Sintered” means that a method for increasing the surface area of the plates has been used in their construction. The electrode materials in bead form are heat-treated and pressed onto a grid substrate. The end result looks like a solid plate but is actually very porous.

As assembled, the anode material is cadmium and the cathode material is nickel hydroxide (Table 2). Charging converts the materials to cadmium hydroxide and nickel oxyhydroxide (Figure 4). The electrolyte is potassium hydroxide, or KOH. The separator is made of two parts, one of cloth (typically nylon) and the other plastic (typically the same woven polypropylene used in primary batteries). This separator has to be “wetted”, or treated to make

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sure that it operates properly during both charge and discharge. Wetting agents are referred to as “surfactants” – a glorified name for soap. So long as the surfactant stays in the separator, it works fine; if any of it dissolves in the electrolyte, foaming will occur during charging.

Cells are usually assembled into a rectangular solid nylon jacket or “cell jar”. The top of the cell jar will have two terminals (positive and negative) and the vent, which is removable so that it can also serve as the access needed to replenish the electrolyte if necessary.

This diagram shows a “sealed” cell; The cell from an aircraft battery would have a removable vent located in the center of this cover.

Figure 9: Rectangular (or “Prismatic”) cell showing multiple parallel electrodes.

Aircraft batteries require 19 of these cells (1.2V X 19 = 22.8V). The exception is the BB-

716/A2 which uses 20 cells. The extra cell has less capacity than the other 19 so that there is a distinct drop in voltage when this cell dies to signal that the end of battery life is near.

The cells are connected by metallic cell straps inside an epoxy-coated steel case. The BB-558/A uses a stainless steel case instead due to demanding inside dimensions that can’t be controlled with the typical epoxy-coated material. The cases include open vents to allow air to pass through; most aircraft batteries are force ventilated through these openings to keep them cool. The cases also house the connection – a two-pronged standard terminal referred to as the “Elcon” connector. Most batteries also include a wiring harness that connects to the aircraft through another, specialty connector. These harnesses typically provide data for the pilot from sensors inside the battery for temperature, voltage, or both.

2 The BB-716/A is now managed by the Defense Supply Center, Richmond, SOS: S9G.

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The wiring harnesses themselves present design challenges to the manufacturer and often result in maintenance problems for the field. All the sensors inside the battery are inter-connected by wires. The wires of the harness are insulated and terminate into some form of connection on either end. Inside a vented aircraft battery, they are constantly exposed to potassium hydroxide and potassium carbonate, both of which are released in small amounts when the vents allow excess air pressure to escape from the cells. These caustic materials attack the wires at the terminations, eventually compromising the integrity of the connection. The end result is a false-negative signal from the battery back to the pilot. (top) Maintenance

The Army divides aircraft battery maintenance duties between Aviation Unit (AVUM) and Aviation Intermediate (AVIM) Maintenance units. The AVUM responsibilities usually include visual inspections and voltage readings. AVUM duties are conducted inside the aircraft with only hand tools and meters available. AVIM responsibilities include preparing new batteries for service, troubleshooting unserviceable batteries, replacing worn or inoperative parts (like connectors, harnesses, or cells), and charging. AVIM duties are conducted in a battery shop.

Vented nickel cadmium batteries can be charged by several methods: How you charge it will depend on which charger you have.

The most widely used method is the 2-step constant current, which can be done with the AN/ASM-137 (PCA131A), NSN 6130-00-759-2882, or the AN/ASM-137A, NSN 6130-00-238-4433, both of which are B16 NSNs. These chargers are designed to provide a high-rate charge up until the battery provides a pre-determined voltage value, and then apply a low-rate charge to top-off the charging cycle.

The other common method is the reverse-pulse charge. This can be done using the RF80H charger, NSN 6130-01-108-5668, managed by FHZ, generally referred to as the Christie ReFlex© Charger (Christie is now owned by Marathon Batteries). This charger also applies a high-rate charge, but occasionally applies a short reverse-pulse to help clear the ions that gather around the electrodes. This pulse method allows for faster charges than the 2-step method.

The last method used, not preferred by anyone who could possibly avoid it, is the forward-pulse charging method performed with the AN/USM-432, NSN 6130-01-236-3106 (B16). It uses the same theory as the RF80H, only it applies a forward pulse of high current. It tends to overheat batteries under charge and itself in the process.

The constant current method is seldom used in the maintenance shop. It’s a last resort, designed to allow charging of batteries when all your regular chargers are broken or occupied. TM 11-6140-203-23 gives the charging current values and time limits for each battery covered by the TM.

Chargers onboard Army aircraft use a 2-step process of a constant current charge (limited by the charger itself) followed by a constant potential charge. The battery is charged by a limited

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current flow until the battery reaches a set voltage value, then by a constant voltage. This method allows the charge current to drop off as the battery voltage rises, and allows a battery to stay fully charged by the potential applied to its terminals, typically referred to as a trickle charge. (top) Commo Batteries Reference: US Army Supply Bulletin SB 11-6, 1 JUN 01. Commo batteries have to fulfill a wide range of needs for the military. They have to work in all climates possible, including the arctic, jungles, and deserts, in every season of the year. They are used individually or in combination with other batteries to power radios, tactical ADP, encoding devices, night vision devices, test sets, transponder sets, mine detectors, and land navigation devices. They have to be ready to go when needed, meaning: (1) be there in sufficient quantity at the beginning of an exercise; (2) Store easily and survive well in storage; (3) be easily transported to where they’re needed; (4) demand as little attention and work as possible; (5) be as light and easy to carry as possible; and (6) be economically feasible (within budget). As if that wasn’t enough, there has to be few types so that military units don’t need a vast array of different batteries to operate. Obviously, no single battery can fulfill all these needs. As a result, CECOM’s commo batteries are a larger and more diversified collection of chemistries and types than our aircraft batteries. Some are primary, some rechargeable. They range in size from 0.7 ounces to 4 pounds. Some are cylindrical in shape, some rectangular, and some have unique shapes all their own. They carry as little as 2.3 Watt-Hours of energy to as much as 170 Watt-Hours. Most store well in all climates, but have limits in how hot or cold they can be and still operate well. And judging from the feedback we get, they all cost too much. In order to cover the specifics, what follows is an abbreviated description of each chemical system used in CECOM commo batteries. For information on testing, charging, or extending the shelf life of any CECOM commo battery, please refer to section 10 of US Army Supply Bulletin SB 11-6. (top) Lithium Sulfur Dioxide (Li/SO2) Lithium sulfur dioxide batteries account for 5-10% of all CECOM sales. They range from a single cell (the BA-5567A/U) at 3.0 volts to 10 cells (BA-5590B/U and BA-5557A/U) with both 15 and 30-volt connections possible. As built, the anode is a ribbon of lithium metal with a copper current collector and a nickel-plated connection tab, a cathode made from a mixture of carbon and Teflon© pressed into an aluminum screen, and a separator made from woven polypropylene. These materials are spirally wound in a “jelly-roll” configuration and placed in a steel can. The can is sealed shut and filled with a mixture of sulfur dioxide, acetonitrile, and lithium bromide salt. The sulfur dioxide acts electrically as the cathode through the physical structure described earlier. The acetonitrile and lithium bromide act as the electrolyte.

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Basic Cell Design Spirally Wound Lithium Primary Cells

Separator: Thin, microporous plastic

Anode

Cathode

Lithium Metal

Current Collector

Anode Tab

Cathode Tab

Carbon & binder pressed into a metal screen (usually aluminum)

Figure 10: Basic components of a spirally wound cell

Sulfur dioxide is a gas at room temperature. In order to work properly, and in order to assure a sufficient quantity of it, this gas must be pressurized in the cell. It is toxic; it can cause respiratory paralysis in high concentrations. However, it has excellent olfactory warning properties (it stinks like hell). Since each cell contains a limited quantity and since sulfur dioxide gas spreads rapidly and quickly reacts with any moisture in the air, the chances of it reaching a dangerous concentration from a battery venting is remote. Anyone overcome by breathing in sulfur dioxide gas will start getting better simply by breathing in clean air. Lithium is highly reactive, capable of bursting in flames when wet. It reacts quickly with water to form lithium hydroxide, a caustic base. Molten lithium will react violently with just about everything. Precautions are necessary in the design and use of all lithium batteries to avoid reaching the melting point of lithium (180°C or 356°F). Completed cells are connected into cell strings with fuses, thermal cutouts and diodes (except for the BA-5567A/U). Cell strings are assembled into the battery jackets, made either from a non-flammable plastic or a flexible material called Mylar©, a multi-layered polyester. Each battery has its own unique connector or terminals.

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Figure 11: Open view of a Hawker BA-5590B/U showing cell and battery component arrangement. All of CECOM’s lithium batteries have a shelf life code of 9, meaning 60 months, extendable. They survive storage well, tolerating temperatures as high as 130°F and even short durations of 160°F. (top) Lithium Manganese Dioxide (Li/MnO2) Lithium manganese dioxide batteries differ from the lithium sulfur dioxide variety in both cathode and electrolyte. The cathode is made with manganese dioxide (a solid) mixed with carbon and a binder (usually Teflon©) and pressed into a conductive, metal screen (not always aluminum). The electrolyte consists of organic solvents with a salt; although the exact components vary, the organic solvents always include a type known as ethers. Ethers are highly flammable. They also can pass easily through the smallest of openings when subjected to high temperatures. These cells also use a woven, microporous separator, although for safety reasons it is usually a mix of polypropylene and polyethylene, referred to as a shut-down separator. Since polyethylene has a lower melting point than polypropylene, the polyethylene will melt sooner yet stay between the layers of polypropylene sealing all the pores and stopping all ionic conduction between the electrodes. The most common type of cell is spirally wound just like the lithium sulfur dioxide cells, and placed in a can that is sealed shut and filled with electrolyte. The Army is currently trying to develop a “pouch” cell, which is usually wound elliptically and sealed in a flexible, soft pouch before filling. These pouches have been subject to leaking ether and swelling, two problems that seem to be nearing resolution. Lithium manganese dioxide cells are assembled into batteries much the same way as their sulfur dioxide counterparts. They also store well, but not for long at temperatures above 160°F. They also have a shelf life of 60 months, extendable. Tests to date have shown that they are most likely to lose low-temperature performance as they age. (top)

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Zinc Air (Zn/O2)

Figure 12: Military zinc-air prototype, showing air vents on either side of connector Zinc air batteries, currently under consideration in military applications, use oxygen from the atmosphere as the cathode and metallic zinc as the anode, usually in a pressed powder form. The cells are constructed with access holes around the cathode area to allow airflow in and out. Since there is no need to pack the active cathode material into the cell, greater energy densities are possible due to more room for the anode (the fuel electrode). In the commercial market, zinc air batteries are button cells used for all applications that would normally take an alkaline button cell. For military applications, the cells planned will be zinc powder mixed with electrolyte and binder, pressed into flat plates inside a shallow plastic dish (called a “buttercup”), and arranged in a rectangular configuration with a porous container that will allow air flow over the surface. While zinc air batteries pack a lot of fuel (energy), they can’t deliver the same amount of power as lithium or nickel metal hydride batteries in similar sizes. In order to obtain the needed current capability, zinc air batteries will need to be larger. Zinc air batteries must have access to air. Getting them wet or closing them inside plastic bags will cause them to shut down. Current experimental models have been able to power military radios with no more air than would be required to allow a small dog to breathe. The shelf life of zinc air batteries depends on maintaining an airtight seal to prevent self-discharge. If the batteries are removed from their packaging, they will experience rapid self-

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discharge. While CECOM has not yet assigned any shelf life codes to zinc air batteries, tests have shown that they can retain 85% of their capacity in casual storage for up to 5 years if kept in an airtight seal. (top) Sealed Nickel Cadmium (NiOOH/Cd(OH)2 abbreviated as NiCd)

Ni Cd Spirally Wound Cell

Nickel Hydroxide

Cadmium

Figure 13: An assembly drawing of a spirally wound nickel cadmium cell Sealed nickel cadmium batteries have a similar chemistry to the aircraft batteries described above, only they are normally wound spirally and placed in steel cans. The cans are closed with a vent mechanism designed to release excess pressure should internal pressure rise during charging. However, unlike the aircraft batteries, it’s best to control charging so that they don’t have to vent. Once they do, some of the electrolyte will be lost which will adversely affect performance. The separators differ in that they are composed of unwoven nylon or polypropylene. The electrolyte is still KOH, but with limited amounts – typically referred to as “starved” electrolyte. Sealed nickel cadmium batteries have excellent power density, capable of providing high current discharges. They don’t, however, carry much energy by volume or weight. Sealed nickel cadmium batteries have a shelf life code of 7, meaning 36 months, extendable. High temperature storage (in excess of 113°F) can cause electrolyte loss, which will result in permanent loss of capacity and possibly affect the integrity of internal battery

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components and connections. They store better when fully discharged; they will be able to tolerate higher temperatures when fully discharged. Charging sealed nickel cadmium batteries can be accomplished either with the old PP-7286/U (NSN 6130-01-041-3490) charger or the new PP-8444A/U charger (NSN 6130-01-443-0970). The former uses a set current value and a timer to turn the charge cycle off. The latter is automatic, depending on a characteristic drop in voltage as the nickel cadmium battery reaches its full charge capacity. Once this slight drop is detected, the PP-8444A/U can switch to a top-off charge to complete the charge cycle. (top) What is “memory”? Memory is said to occur when a nickel-based rechargeable battery is repeatedly discharged to the same level prior to charging. The unused portion of the electrodes undergoes a change in the crystal structure, making it difficult to use should a discharge cycle finally place a demand on it (the same thing can happen to the entire electrode during long-term storage). The fix is to deep-discharge the battery, which will discharge at a lower than normal voltage once the memory has taken place. It is more of a problem in nickel-cadmium batteries than in nickel metal hydride batteries since both electrodes are subject to the change. Sealed Nickel Metal Hydride (abbreviated as NiMH) Nickel metal hydride cells use hydrogen as the anode. Only instead of obtaining it from the atmosphere, it’s provided by compounds of hydrogen and a variety of metals. The cathode is nickel hydroxide that converts to nickel oxyhydroxide in charging. The electrolyte is again KOH, in the “starved” configuration. Nickel metal hydride cells also provide good power density. They are an improvement in energy density compared to the sealed nickel cadmium batteries. However, the self-discharge they experience sitting on the shelf is the worst of any CECOM battery. Nickel metal hydride batteries also have a shelf life code of 7 (36 months, extendable). When charged, they have the least tolerance of any battery to high temperature storage due to an amount of free hydrogen in the cells. When fully discharged, they can tolerate temperatures up to 122°F. However, they too can lose electrolyte in hot conditions, resulting in irreversible damage. Charging should3 only be done on the PP-8444A/U. It applies a charge in two stages, similar to the charge method used for sealed nickel cadmium. Only instead of a voltage drop, it keys on rising battery temperature to switch to the top-off charge mode. (top) Lithium Ion Unlike the primary lithium batteries, lithium ion rechargeables do not contain any metallic lithium. The lithium is in compound. While there are several possible compounds that can be used, the most common is lithiated cobalt dioxide, or lithium cobaltite (LiCoO2). This

3 NiMH batteries can be charged by any method that charges them at a slow rate. For optimum performance, use the PP-8444A/U whenever possible.

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compound is used to build the cathode. The anode is built with carbon held to a support structure with a binder. Electrodes are spirally wound. Charging causes separation of the compound into lithium and cobalt dioxide ions. The lithium then migrates through the electrolyte to the anode and reacts with the carbon. Lithium ion batteries have much better energy density than their nickel-based counterparts but don’t have the equivalent power density (see Table 3). Unlike the nickel-based chemistries, lithium ion batteries store best when charged. In fact, being completely discharged is a problem that could adversely affect performance. If left in this discharged condition, they won’t last long at all. Lithium ion batteries are more tolerant of high temperature storage conditions than the nickel-based batteries. Lithium ion batteries must not be over-charged. While the nickel cadmium batteries require some overcharge for proper operation, it could damage lithium ion batteries. A typical charge method would be a constant current charge until the battery reaches a set voltage followed by a constant potential charge to the charge end-voltage, typically 4.10 volts per cell. There is no trickle charge applied to lithium ion batteries. The PP-8444A/U should be used to charge CECOM lithium ion batteries. Self discharge is the shelf life limiting factor. Although a lithium ion cell has excellent self-discharge characteristics compared to other rechargeable cells, lithium ion cells come in packs with protective circuits that stop potentially harmful situations from occurring. Unfortunately, this circuitry slowly uses up the energy in lithium ion batteries. Once the cells discharge to 2.5 volts, they must be charged immediately or they will be useless. CECOM’s lithium ion battery (the BB-2847/U) is rated for an extendable 36-month shelf life. CECOM will soon have other lithium ion batteries available, including an equivalent to the BA-5590B and BB-390A configurations. (top)

Appendix A

Periodic Table (next page)

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Periodic Table of the Elements Alkali

Halogens Inert

Metals Gases I A O

1.008 4.003

H HeHydrogen Helium

1 II A III A IV A V A VI A VII A 2 6.94 9.013 10.82 12.01 14.008 16 19 20.183

Li Be B C N O F Ne Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon

3 4 5 6 7 8 9 10

22.991 24.32 26.98 28.09 30.975 32.066 35.457 39.944

Na Mg Al Si P S Cl ArSodium Magnesium Aluminum Silicon Phosphorus Sulfur Chlorine Argon

11 12 III B IV B V B VI B VII B VIII I B II B 13 14 15 16 17 18

39.1 40.08 44.96 47.9 50.95 52.01 54.94 55.85 58.94 58.69 63.54 65.38 69.72 72.6 74.91 78.96 79.916 83.8

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrPotassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

85.48 87.63 88.92 91.22 92.91 95.95 98 101.1 102.91 106.7 107.88 112.41 114.76 118.7 121.76 127.61 126.91 131.3

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I XeRubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

132.91 137.36 138.92 178.6 180.95 183.92 186.31 190.2 192.2 195.23 197.967 200.61 204.39 207.21 208.98 209.983 209.987 222

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At RnCesium Barium Lanthanum Hafnium Tantalum Wolfram Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon

55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

223.02 226.05 227 261.11 262.114 263.118 262.123 265 266

Fr Ra Ac Rf Db Sg Bh Hs MtFrancium Radium Actinium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium

87 88 89 104 105 106 107 108 109

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140.13 140.92 144.27 144.913 150.43 151.964 156.9 158.93 162.46 164.94 168.94 169.4 173.04 174.99

Lanthanide Series: Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium

58 59 60 61 62 63 64 65 66 67 68 69 70 71

232.05 231.036 238.07 237.048 244.064 243.06 247.07 247.07 251.08 252.08 257.095 256.094 259.1 262.105

Actinide Series: Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No LrThorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium

90 91 92 93 94 95 96 97 98 99 100 101 102 103

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Appendix B

Glossary of Terms Anions – Ions that have gained at least one electron from another atom and are therefore negatively charged. Anode – The negative electrode in a voltaic cell that gives up its electrons to the external circuit and is oxidized in the process. Atom – The smallest particle of an element that retains the characteristics of that element. Cathode – The positive electrode in a voltaic cell that accepts electrons from the external circuit and is reduced in the process. Cations – Ions that have lost at least one electron and therefore have a positive charge. Coulomb – A quantity of 6.28 X 1018 or 6,280,000,000,000,000,000 (six quintillion, two hundred and eighty quadrillion). Current – The flow of electrons through an electric circuit. Measured in amperes. One ampere is equal to one coulomb of electrons moving through one point in one second. Electrodes – In an electrochemical cell, the materials that provide the electron flow to the external circuit. There are two electrodes in an electrochemical cell: The anode and the cathode. Electrolyte – The medium that allows ionic conduction between the electrodes of an electrochemical cell. Electron – A negatively charged particle that orbits the nucleus of an atom. Energy – The work that a physical system is capable of doing in changing from its actual state to a specified reference state. For batteries, this means using the chemical (potential) energy to generate electric energy. Energy Density – The amount of energy, typically expressed in watt-hours, relative to either the volume (liters) or weight (kilograms). Impedance – The total opposition offered to the flow of current in an electric circuit. It is a combination of the resistance of the circuit components and the reactance offered by any capacitive or inductive properties of the circuit’s components. Inert Gases – The gases of group O (or group VIIIA) of the periodic table, these gases do not react with any other element(s) to form compounds. This is due to their full valence shells.

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They are: Helium, Neon, Argon, Krypton, and Xenon (Radon, a radioactive gas, is also in this group). Ions – Atoms that have either lost or gained one or more electrons by giving them to or taking them from another atom. Neutron – A particle with no electric charge that resides in the nucleus of an atom. Parallel (connection) – When two or more cells are connected to each other by connecting all their negative outputs together and all their positive outputs together. Power – The measure of work being done. Work is done whenever a force causes a motion. In an electric circuit, voltage causes the motion of electrons. Electric power is measured in watts and can be derived by multiplying the voltage and current in an electric circuit. Proton – A positively charged particle that resides in the nucleus of an atom. REDOX – Or oxidation-reduction, the transfer of electrons from one material to another. Resistance – The opposition to current flow offered by an electric circuit or a component in a circuit. Resistance is a physical property and can be measured in ohms. Series (connection) – When two or more cells are connected to each other by connecting the negative output from one cell to the positive terminal of the next. Specific Gravity – The density of a fluid relative to water, with pure water being equal to 1. More dense fluids will have a greater specific gravity; less dense fluids will have a smaller specific gravity. Valence – The outermost shell of electrons orbiting the nucleus of an atom. Voltage – Or Electromotive Force, the potential energy that exists between two points. One volt is said to exist when that potential equals one coulomb of electrons. Wiring Diagram – A method for using symbols to represent the individual components of an electric circuit and how they are connected with one another. (top)

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Appendix C

References T. Atwater & A. Salkind, Primary Cells, Wiley Encyclopedia, New York, 2000 D. Linden, Ed., Handbook of Batteries, 2d. Ed., McGraw-Hill Book Co., New York, 1995 US Army Field Manual FM 11-60, Basic Principles, Direct Current, Nov 1982 (out of print) US Army Supply Bulletin SB 11-6, Communications Electronics Batteries, Supply and Management Data, 01 Jun 2001, PIN 079041. US Army Technical Manual, TM 11-6140-203-23, Aviation Unit and Intermediate Maintenance manual for Aircraft Nickel Cadmium Batteries, 15 Jul 1994 with Change 2, 01 Feb 1996, PIN 072947. NOTE: Both SB 11-6 and TM 11-6140-203-23 are available at the US Army Logistics Support Activity Website, http://www.logsa.army.mil. A username and password are required to gain access to either document. (top)

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