Worst Post Ever (1047 hits)
Category: GeneralRating: -1.4 on 15 reviews (Rate this item) (V)
Submitted by WillZone (View user info) at 2004-04-15 15:33:57 EDT
Warning, the folowing is nothing. Please divert your nipples
Hello How is everyone. Here is something that is interesting
Title: New Technology Batteries Guide: NIJ Guide 200-98.
Series: NIJ Guide
Author: William J. Ingram
Published: October 1998
Subject: Technology in law enforcement
58 pages
120,000 bytes
-------------------------------
Some figures, charts, forms, equations, and tables are not included in this
ASCII plain-text file. To view this document in its entirety, download the
Adobe Acrobat graphic file available from this Web site or order a print
copy from NCJRS at 800-851-3420.
-------------------------------
U.S. Department of Justice
Office of Justice Programs
National Institute of Justice
Jeremy Travis
Director
-------------------------------
New Technology Batteries Guide
NIJ Guide 200-98
William J. Ingram
Institute for Telecommunication Sciences
Boulder, CO 80303
Prepared for:
National Institute of Justice
Office of Science and Technology
U.S. Department of Justice
Washington, DC 20531
October 1998
-------------------------------
The Technical effort to develop this Guide was conducted under
Interagency Agreement 94-IJ-R-004 Project No. 97-027-CTT.
This Guide was prepared by the Office of Law Enforcement Standards
(OLES) of the National Institute of Standards and Technology (NIST)
under the direction of A. George Lieberman, Program Manager for
Communications Systems, and Kathleen M. Higgins, Director of OLES.
The work resulting in this guide was sponsored by the National Institute of
Justice, David G. Boyd, Director, Office of Science and Technology.
------------------------------
FOREWORD
The Office of Law Enforcement Standards (OLES) of the National
Institute of Standards and Technology furnishes technical support to the
National Institute of Justice program to strengthen law enforcement and
criminal justice in the United States. OLES's function is to conduct
research that will assist law enforcement and criminal justice agencies in
the selection and procurement of quality equipment.
OLES is: (1) subjecting existing equipment to laboratory testing and
evaluation, and (2) conducting research leading to the development of
several series of documents, including national standards, user guides, and
technical reports.
This document covers research conducted by OLES under the sponsorship
of the National Institute of Justice. Additional reports as well as other
documents are being issued under the OLES program in the areas of
protective clothing and equipment, communications systems, emergency
equipment, investigative aids, security systems, vehicles, weapons, and
analytical techniques and standard reference materials used by the forensic
community.
Technical comments and suggestions concerning this report are invited
from all interested parties. They may be addressed to the Director, Office
of Law Enforcement Standards, National Institute of Standards and
Technology, Gaithersburg, MD 20899.
David G. Boyd, Director
Office of Science and Technology
National Institute of Justice
-------------------------------
BACKGROUND
The Office of Law Enforcement Standards (OLES) was established by the
National Institute of Justice (NIJ) to provide focus on two major
objectives: (1) to find existing equipment which can be purchased today,
and (2) to develop new law-enforcement equipment which can be made
available as soon as possible. A part of OLES's mission is to become
thoroughly familiar with existing equipment, to evaluate its performance
by means of objective laboratory tests, to develop and improve these
methods of test, to develop performance standards for selected equipment
items, and to prepare guidelines for the selection and use of this
equipment. All of these activities are directed toward providing law
enforcement agencies with assistance in making good equipment
selections and acquisitions in accordance with their own requirements.
As the OLES program has matured, there has been a gradual shift in the
objectives of the OLES projects. The initial emphasis on the development
of standards has decreased, and the emphasis on the development of
guidelines has increased. For the significance of this shift in emphasis to
be appreciated, the precise definitions of the words "standard" and
"guideline" as used in this context must be clearly understood.
A "standard" for a particular item of equipment is understood to be a
formal document, in a conventional format, that details the performance
that the equipment is required to give, and describes test methods by
which its actual performance can be measured. These requirements are
technical, and are stated in terms directly related to the equipment's use.
The basic purposes of a standard are (1) to be a reference in procurement
documents created by purchasing officers who wish to specify equipment
of the "standard" quality, and (2) to identify objectively equipment of
acceptable performance.
Note that a standard is not intended to inform and guide the reader; that is
the function of a "guideline." Guidelines are written in non-technical
language and are addressed to the potential user of the equipment. They
include a general discussion of the equipment, its important performance
attributes, the various models currently on the market, objective test data
where available, and any other information that might help the reader
make a rational selection among the various options or alternatives
available to him or her.
This battery guide is provided to inform the reader of the latest technology
related to battery composition, battery usage, and battery charging
techniques.
Kathleen Higgins
National Institute of Standards and Technology
March 27, 1997
-------------------------------
CONTENTS
FOREWORD
BACKGROUND
1. FUNDAMENTALS OF BATTERY TECHNOLOGY
1.1 WHAT IS A BATTERY?
1.2 How Does a Battery Work?
1.3 Galvanic Cells vs. Batteries
1.4 Primary Battery
1.5 Secondary Battery
1.6 Battery Labels
2. AVAILABLE BATTERY TYPES
2.1 General
2.1.1 Acid vs. Alkaline
2.1.2 Wet vs. Dry
2.1.3 Categories
2.2 Vehicular Batteries
2.2.1 Lead-Acid
2.2.2 Sealed vs. Flooded
2.2.3 Deep-Cycle Batteries
2.2.4 Battery Categories for Vehicular Batteries
2.3 "Household" Batteries
2.3.1 Zinc-carbon (Z-C)
2.3.2 Zinc-Manganese Dioxide Alkaline Cells ("Alkaline Batteries")
2.3.3 Rechargeable Alkaline Batteries
2.3.4 Nickel-Cadmium (Ni-Cd)
2.3.5 Nickel-Metal Hydride (Ni-MH)
2.3.6 Nickel-Iron (Ni-I)
2.3.7 Nickel-Zinc (Ni-Z)
2.3.8 Lithium and Lithium Ion
2.4 Specialty Batteries ("Button" and Miniature Batteries)
2.4.1 Metal-Air Cells
2.4.2 Silver Oxide
2.4.3 Mercury Oxide
2.5 Other Batteries
2.5.1 Nickel-Hydrogen (Ni-H)
2.5.2 Thermal Batteries
2.5.3 Super Capacitor
2.5.4 The Potato Battery
2.5.5 The Sea Battery
2.5.6 Other Developments
3. PERFORMANCE, ECONOMICS AND TRADEOFFS
3.1 Energy Densities
3.2 Energy per Mass
3.3 Energy Per Volume
3.4 Memory Effects
3.5 Voltage Profiles
3.6 Self-Discharge Rates
3.7 Operating Temperatures
3.8 Cycle Life
3.9 Capacity Testing
3.10 Battery Technology Comparison
4. SELECTING THE RIGHT BATTERY FOR THE APPLICATION
4.1 Battery Properties
4.2 Environmental Concerns
4.3 Standardization
4.4 Testing Capacities
4.5 Mobile Radios
4.6 Cellular Phones and PCS Phones
4.7 Laptop Computers
4.8 Camcorders
4.9 Summary
5. BATTERY HANDLING AND MAINTENANCE
5.1 Battery Dangers
5.2 Extending Battery Life
6. BATTERY CHARGERS AND ADAPTERS
6.1 Battery Chargers
6.2 Charge Rates
6.3 Charging Techniques
6.4 Charging Lead-Acid Batteries
6.5 Charging Ni-Cd Batteries
6.6 Timed-Charge Charging
6.7 Pulsed Charge-Discharge Chargers
6.8 Charging Button Batteries
6.9 Internal Chargers
6.10 Battery Testers
6.11 "Smart" Batteries
6.12 End of Life
6.13 Battery Adapters
7. PRODUCTS AND SUPPLIERS
7.1 Battery Manufacturers
7.1.1 Battery Engineering
7.1.2 Duracell
7.1.3 Eveready
7.1.4 Rayovac
8. A GLOSSARY OF BATTERY TERMS
9. BIBLIOGRAPHY
LIST OF FIGURES
(Figures are not available in this ASCII file)
Figure 1. Conceptual diagram of a galvanic cell.
Figure 2. Energy densities, W@h/kg, of various battery types (adapted
from NAVSO P-3676).
Figure 3. Energy densities, W@h/L, of various battery types (adapted
from NAVSO P-3676).
Figure 4. Flat discharge curve vs. sloping discharge curve.
Figure 5. Performance comparison of primary and secondary alkaline and
Ni-Cd batteries (adapted from Design Note: Renewable Reusable Alkaline
Batteries).
LIST OF TABLES
(Tables are not available in their original format; table 4 is not available in
this ASCII file)
Table 1. The Electromotive Series for Some Battery Components
Table 2. Various Popular Household-Battery Sizes
Table 3. Battery Technology Comparison (adapted from Design Note:
Renewable Reusable Alkaline Batteries)
Table 4. A Comparison of Several Popular Battery Types
Table 5. Recommended Battery Types for Various Usage Conditions
Table 6. Typical Usage of Portable Telecommunications Equipment.
Table 7. Charge Rate Descriptions
Table 8. Some On-Line Information Available via the World Wide Web
LIST OF EQUATIONS
(Equations are not available in this ASCII file)
Equation 1. The chemical reaction in a lead-acid battery.
Equation 2. The chemical reaction in a Leclanch‚ cell.
Equation 3. The chemical reaction in a nickel-cadmium battery.
Equation 4. The chemical reaction in a lithium-manganese dioxide cell.
-------------------------------
1. FUNDAMENTALS OF BATTERY TECHNOLOGY
1.1. What is a Battery?
A battery, in concept, can be any device that stores energy for later use. A
rock, pushed to the top of a hill, can be considered a kind of battery, since
the energy used to push it up the hill (chemical energy, from muscles or
combustion engines) is converted and stored as potential kinetic energy at
the top of the hill. Later, that energy is released as kinetic and thermal
energy when the rock rolls down the hill.
Common use of the word, "battery," however, is limited to an
electrochemical device that converts chemical energy into electricity, by
use of a galvanic cell. A galvanic cell is a fairly simple device consisting
of two electrodes (an anode and a cathode) and an electrolyte solution.
Batteries consist of one or more galvanic cells.
1.2. How Does a Battery Work?
Figure 1 shows a simple galvanic cell. Electrodes (two plates, each made
from a different kind of metal or metallic compound) are placed in an
electrolyte solution. External wires connect the electrodes to an electrical
load (a light bulb in this case). The metal in the anode (the negative
terminal) oxidizes (i.e., it "rusts"), releasing negatively charged electrons
and positively charged metal ions. The electrons travel through the wire
(and the electrical load) to the cathode (the positive terminal). The
electrons combine with the material in the cathode. This combination
process is called reduction, and it releases a negatively charged
metal-oxide ion. At the interface with the electrolyte, this ion causes a
water molecule to split into a hydrogen ion and a hydroxide ion. The
positively charged hydrogen ion combines with the negatively charged
metal-oxide ion and becomes inert. The negatively charged hydroxide ion
flows through the electrolyte to the anode where it combines with the
positively charged metal ion, forming a water molecule and a metal-oxide
molecule.
In effect, metal ions from the anode will "dissolve" into the electrolyte
solution while hydrogen molecules from the electrolyte are deposited onto
the cathode. When the anode is fully oxidized or the cathode is fully
reduced, the chemical reaction will stop and the battery is considered to be
discharged.
Recharging a battery is usually a matter of externally applying a voltage
across the plates to reverse the chemical process. Some chemical reactions,
however, are difficult or impossible to reverse. Cells with irreversible
reactions are commonly known as primary cells, while cells with
reversible reactions are known as secondary cells. It is dangerous to
attempt to recharge primary cells.
The amount of voltage and current that a galvanic cell produces is directly
related to the types of materials used in the electrodes and electrolyte. The
length of time the cell can produce that voltage and current is related to the
amount of active material in the cell and the cell's design.
Every metal or metal compound has an electromotive force, which is the
propensity of the metal to gain or lose electrons in relation to another
material. Compounds with a positive electromotive force will make good
anodes and those with a negative force will make good cathodes. The
larger the difference between the electromotive forces of the anode and
cathode, the greater the amount of energy that can be produced by the cell.
Table 1 shows the electromotive force of some common battery
components.
--------------------
Table 1. The Electromotive Series for Some Battery Components
Anode Materials
(Listed from worst [most positive] to best [most negative])
1. Gold; 2. Platinum; 3. Mercury; 4. Palladium; 5. Silver; 6. Copper; 7.
Hydrogen; 8. Lead; 9. Tin; 10. Nickel; 11. Iron; 12. Chromium; 13. Zinc;
14. Aluminum; 15. Magnesium; 16. Lithium
Cathode Materials
(Listed from best [most positive] to worst [most negative])
1. Ferrate; 2. Iron Oxide; 3. Cuprous Oxide; 4. Iodate; 5. Cupric Oxide; 6.
Mercuric Oxide; 7. Cobaltic Oxide; 8. Manganese Dioxide; 9. Lead
Dioxide; 10. Silver Oxide; 11. Oxygen; 12. Nickel Oxyhydroxide; 13.
Nickel Dioxide; 14. Silver Peroxide; 15. Permanganate; 16. Bromate
-------------------------------
Over the years, battery specialists have experimented with many different
combinations of material and have generally tried to balance the potential
energy output of a battery with the costs of manufacturing the battery.
Other factors, such as battery weight, shelf life, and environmental impact,
also enter into a battery's design.
1.3. Galvanic Cells vs. Batteries
From earlier discussion, we know that a battery is one or more galvanic
cells connected in series or in parallel.
A battery composed of two 1.5 V galvanic cells connected in series, for
example, will produce 3 V. A typical 9 V battery is simply six 1.5 V cells
connected in series. Such a series battery, however, will produce a current
that is the equivalent to just one of the galvanic cells.
A battery composed of two 1.5 V galvanic cells connected in parallel, on
the other hand, will still produce a voltage of 1.5 V, but the current
provided can be double the current that just one cell would create. Such a
battery can provide current twice as long as a single cell.
Many galvanic cells can be thus connected to create a battery with almost
any current at any voltage level.
1.4. Primary Battery
A primary battery is a battery that is designed to be cycled (fully
discharged) only once and then discarded. Although primary batteries are
often made from the same base materials as secondary (rechargeable)
batteries, the design and manufacturing processes are not the same.
Battery manufacturers recommend that primary batteries not be recharged.
Although attempts at recharging a primary battery will occasionally
succeed (usually with a diminished capacity), it is more likely that the
battery will simply fail to hold any charge, will leak electrolyte onto the
battery charger, or will overheat and cause a fire. It is unwise and
dangerous to recharge a primary battery.
1.5. Secondary Battery
A secondary battery is commonly known as a rechargeable battery. It is
usually designed to have a lifetime of between 100 and 1000 recharge
cycles, depending on the composite materials.
Secondary batteries are, generally, more cost effective over time than
primary batteries, since the battery can be recharged and reused. A single
discharge cycle of a primary battery, however, will provide more current
for a longer period of time than a single discharge cycle of an equivalent
secondary battery.
1.6. Battery Labels
The American National Standards Institute (ANSI) Standard, ANSI
C18.1M-1992, lists several battery features that must be listed on a
battery's label. They are:
-- Manufacturer -- The name of the battery manufacturer.
-- ANSI Number -- The ANSI/NEDA number of the battery.
-- Date -- The month and year that the battery was manufactured or the
month and year that the battery "expires" (i.e., is no longer guaranteed by
the manufacturer).
-- Voltage -- The nominal battery voltage.
-- Polarity -- The positive and negative terminals. The terminals must be
clearly marked.
-- Warnings -- Other warnings and cautions related to battery usage and
disposal.
-------------------------------
2. AVAILABLE BATTERY TYPES
2.1. General
2.1.1. Acid vs. Alkaline
Batteries are often classified by the type of electrolyte used in their
construction. There are three common classifications: acid, mildly acid,
and alkaline.
Acid-based batteries often use sulphuric acid as the major component of
the electrolyte. Automobile batteries are acid-based. The electrolyte used
in mildly acidic batteries is far less corrosive than typical acid-based
batteries and usually includes a variety of salts that produce the desired
acidity level. Inexpensive household batteries are mildly acidic batteries.
Alkaline batteries typically use sodium hydroxide or potassium hydroxide
as the main component of the electrolyte. Alkaline batteries are often used
in applications where long-lasting, high-energy output is needed, such as
cellular phones, portable CD players, radios, pagers, and flash cameras.
2.1.2. Wet vs. Dry
"Wet" cells refer to galvanic cells where the electrolyte is liquid in form
and is allowed to flow freely within the cell casing. Wet batteries are often
sensitive to the orientation of the battery. For example, if a wet cell is
oriented such that a gas pocket accumulates around one of the electrodes,
the cell will not produce current. Most automobile batteries are wet cells.
"Dry" cells are cells that use a solid or powdery electrolyte. These kind of
electrolytes use the ambient moisture in the air to complete the chemical
process. Cells with liquid electrolyte can be classified as "dry" if the
electrolyte is immobilized by some mechanism, such as by gelling it or by
holding it in place with an absorbent substance such as paper.
In common usage, "dry cell" batteries will usually refer to zinc-carbon
cells (Sec. 2.3.1) or zinc- alkaline-manganese dioxide cells (Sec. 2.3.2),
where the electrolyte is often gelled or held in place by absorbent paper.
Some cells are difficult to categorize. For example, one type of cell is
designed to be stored for long periods without its electrolyte present. Just
before power is needed from the cell, liquid electrolyte is added.
2.1.3. Categories
Batteries can further be classified by their intended use. The following
sections discuss four generic categories of batteries; "vehicular" batteries
(Sec. 2.2), "household" batteries (Sec. 2.3), "specialty" batteries (Sec. 2.4),
and "other" batteries (Sec. 2.5). Each section will focus on the general
properties of that category of battery.
Note that some battery types (acidic or alkaline, wet or dry) can fall into
several different categories. For this guideline, battery types are placed
into the category in which they are most likely to be found in commercial
usage.
2.2. Vehicular Batteries
This section discusses battery types and configurations that are typically
used in motor vehicles. This category can include batteries that drive
electric motors directly or those that provide starting energy for
combustion engines. This category will also include large, stationary
batteries used as power sources for emergency building lighting,
remote-site power, and computer back up.
Vehicular batteries are usually available off-the-shelf in standard designs
or can be custom built for specific applications.
2.2.1. Lead-Acid
Lead-acid batteries, developed in the late 1800s, were the first
commercially practical batteries. Batteries of this type remain popular
because they are relatively inexpensive to produce and sell. The most
widely known uses of lead-acid batteries are as automobile batteries.
Rechargeable lead-acid batteries have become the most widely used type
of battery in the world--more than 20 times the use rate of its nearest
rivals. In fact, battery manufacturing is the single largest use for lead in the
world.[1]
Equation 1 shows the chemical reaction in a lead-acid cell.
Lead-acid batteries remain popular because they can produce high or low
currents over a wide range of temperatures, they have good shelf life and
life cycles, and they are relatively inexpensive to manufacture. Lead-acid
batteries are usually rechargeable.
Lead-acid batteries come in all manner of shapes and sizes, from
household batteries to large batteries for use in submarines. The most
noticeable shortcomings of lead-acid batteries are their relatively heavy
weight and their falling voltage profile during discharge (Sec. 3.5).
2.2.2. Sealed vs. Flooded
In "flooded" batteries, the oxygen created at the positive electrode is
released from the cell and vented into the atmosphere. Similarly, the
hydrogen created at the negative electrode is also vented into the
atmosphere. The overall result is a net loss of water (H2O) from the cell.
This lost water needs to be periodically replaced. Flooded batteries must
be vented to prevent excess pressure from the build up of these gases.
Also, the room or enclosure housing the battery must be vented, since a
concentrated hydrogen and oxygen atmosphere is explosive.
In sealed batteries, however, the generated oxygen combines chemically
with the lead and then the hydrogen at the negative electrode, and then
again with reactive agents in the electrolyte, to recreate water. The net
result is no significant loss of water from the cell.
2.2.3. Deep-Cycle Batteries
Deep-cycle batteries are built in configurations similar to those of regular
batteries, except that they are specifically designed for prolonged use
rather than for short bursts of use followed by a short recycling period.
The term "deep-cycle" is most often applied to lead-acid batteries. Deep-
cycle batteries require longer charging times, with lower current levels,
than is appropriate for regular batteries.
As an example, a typical automobile battery is usually used to provide a
short, intense burst of electricity to the automobile's starter. The battery is
then quickly recharged by the automobile's electrical system as the engine
runs. The typical automobile battery is not a deep-cycle battery.
A battery that provides power to a recreational vehicle (RV), on the other
hand, would be expected to power lights, small appliances, and other
electronics over an extended period of time, even while the RV's engine is
not running. Deep-cycle batteries are more appropriate for this type of
continual usage.
2.2.4. Battery Categories for Vehicular Batteries Vehicular, lead-acid
batteries are further grouped (by typical usage) into three different
categories:
-- Starting-Lighting-Ignition (SLI) -- Typically, these batteries are used for
short, quick-burst, high-current applications. An example is an automotive
battery, which is expected to provide high current, occasionally, to the
engine's starter.
-- Traction -- Traction batteries must provide moderate power through
many deep discharge cycles. One typical use of traction batteries is to
provide power for small electric vehicles, such as golf carts. This type of
battery use is also called Cycle Service.
-- Stationary -- Stationary batteries must have a long shelf life and deliver
moderate to high currents when called upon. These batteries are most often
used for emergencies. Typical uses for stationary batteries are in
uninterruptible power supplies (UPS) and for emergency lighting in
stairwells and hallways. This type of battery use is also called Standby or
Float.
2.3. "Household" Batteries
"Household" batteries are those batteries that are primarily used to power
small, portable devices such as flashlights, radios, laptop computers, toys,
and cellular phones. The following subsections describe the technologies
for many of the formerly used and presently used types of household
batteries.
Typically, household batteries are small, 1.5 V cells that can be readily
purchased off the shelf. These batteries come in standard shapes and sizes
as shown in Table 2. They can also be custom designed and molded to fit
any size battery compartment (e.g., to fit inside a cellular phone,
camcorder, or laptop computer).
-------------------------------
Table 2. Various Popular Household-Battery Sizes
Size: Shape and Dimensions; Voltage
D: Cylindrical, 61.5 mm tall, 34.2 mm diameter; 1.5 V
C: Cylindrical, 50.0 mm tall, 26.2 mm diameter; 1.5 V
AA: Cylindrical, 50.5 mm tall, 14.5 mm diameter; 1.5 V
AAA: Cylindrical, 44.5 mm tall, 10.5 mm diameter; 1.5 V
9 Volt: Rectangular, 48.5 mm tall, 26.5 mm wide, 17.5 mm deep; 9 V
-------------------------------
Most of the rest of this guideline will focus on designs, features, and uses
of household batteries.
2.3.1. Zinc-carbon (Z-C)
Zinc-carbon cells, also known as "Leclanch‚ cells" are widely used
because of their relatively low cost. Equation 2 shows the chemical
reaction in a Leclanch‚ cell. They were the first widely available
household batteries. Zinc-carbon cells are composed of a manganese
dioxide and carbon cathode, a zinc anode, and zinc chloride (or
ammonium chloride) as the electrolyte.
Generally, zinc-carbon cells are not rechargeable and they have a sloping
discharge curve (i.e., the voltage level decreases relative to the amount of
discharge). Zinc-carbon cells will produce 1.5 V, and they are mostly used
for non-critical uses such as small household devices like flashlights and
portable personal radios.
One notable drawback to these kind of batteries is that the outer, protective
casing of the battery is made of zinc. The casing serves as the anode for
the cell and, in some cases, if the anode does not oxidize evenly, the
casing can develop holes that allow leakage of the mildly acidic electrolyte
which can damage the device being powered.
2.3.2. Zinc-Manganese Dioxide Alkaline Cells ("Alkaline Batteries")
When an alkaline electrolyte--instead of the mildly acidic electrolyte--is
used in a regular zinc- carbon battery, it is called an "alkaline" battery. An
alkaline battery can have a useful life of five to six times that of a
zinc-carbon battery. One manufacturer estimates that 30% of the
household batteries sold in the world today are zinc-manganese dioxide
(i.e., alkaline) batteries.[2],[3]
2.3.3. Rechargeable Alkaline Batteries
Like zinc-carbon batteries, alkaline batteries are not generally
rechargeable. One major battery manufacturer, however, has designed a
"reusable alkaline" battery that they market as being rechargeable "25
times or more."[4]
This manufacturer states that its batteries do not suffer from memory
effects as the Ni-Cd batteries do, and that their batteries have a shelf life
that is much longer than Ni-Cd batteries--almost as long as the shelf life of
primary alkaline batteries.
Also, the manufacturer states that their rechargeable alkaline batteries
contain no toxic metals, such as mercury or cadmium, to contribute to the
poisoning of the environment.
Rechargeable alkaline batteries are most appropriate for low- and
moderate-power portable equipment, such as hand-held toys and radio
receivers.
2.3.4. Nickel-Cadmium (Ni-Cd)
Nickel-cadmium cells are the most commonly used rechargeable
household batteries. They are useful for powering small appliances, such
as garden tools and cellular phones. The basic galvanic cell in a Ni-Cd
battery contains a cadmium anode, a nickel hydroxide cathode, and an
alkaline electrolyte. Equation 3 shows the chemical reaction in a Ni-Cd
cell. Batteries made from Ni-Cd cells offer high currents at relatively
constant voltage and they are tolerant of physical abuse. Nickel-cadmium
batteries are also tolerant of inefficient usage cycling. If a Ni-Cd battery
has incurred memory loss (Sec. 3.4), a few cycles of discharge and
recharge can often restore the battery to nearly "full" memory.
Unfortunately, nickel-cadmium technology is relatively expensive.
Cadmium is an expensive metal and is toxic. Recent regulations limiting
the disposal of waste cadmium (from cell manufacturing or from disposal
of used batteries) has contributed to the higher costs of making and using
these batteries.
These increased costs do have one unexpected advantage. It is more cost
effective to recycle and reuse many of the components of a Ni-Cd battery
than it is to recycle components of other types of batteries. Several of the
major battery manufacturers are leaders in such recycling efforts.
2.3.5. Nickel-Metal Hydride (Ni-MH)
Battery designers have investigated several other types of metals that
could be used instead of cadmium to create high-energy secondary
batteries that are compact and inexpensive. The nickel- metal-hydride cell
is a widely used alternative.
The anode of a Ni-MH cell is made of a hydrogen storage metal alloy, the
cathode is made of nickel oxide, and the electrolyte is a potassium
hydroxide solution.
According to one manufacturer, Ni-MH cells can last 40% longer than the
same size Ni-Cd cells and will have a life-span of up to 600 cycles.[5]
This makes them useful for high-energy devices such as laptop computers,
cellular phones, and camcorders.
Ni-MH batteries have a high self-discharge rate and are relatively
expensive.
2.3.6. Nickel-Iron (Ni-I)
Nickel-iron cells, also known as the Edison battery, are much less
expensive to build and to dispose of than nickel-cadmium cells.
Nickel-iron cells were developed even before the nickel- cadmium cells.
The cells are rugged and reliable, but do not recharge very efficiently.
They are widely used in industrial settings and in eastern Europe, where
iron and nickel are readily available and inexpensive.
2.3.7. Nickel-Zinc (Ni-Z)
Another alternative to using cadmium electrodes is using zinc electrodes.
Although the nickel- zinc cell yields promising energy output, the cell has
some unfortunate performance limitations that prevent the cell from
having a useful lifetime of more than 200 or so charging cycles. When
nickel-zinc cells are recharged, the zinc does not redeposit in the same
"holes" on the anode that were created during discharge. Instead, the zinc
redeposits in a somewhat random fashion, causing the electrode to become
misshapen. Over time, this leads to the physical weakening and eventual
failure of the electrode.
2.3.8. Lithium and Lithium Ion
Lithium is a promising reactant in battery technology, due to its high
electropositivity. The specific energy of some lithium-based cells can be
five times greater than an equivalent-sized lead-acid cell and three times
greater than alkaline batteries.[6] Lithium cells will often have a starting
voltage of 3.0 V. These characteristics translate into batteries that are
lighter in weight, have lower per-use costs, and have higher and more
stable voltage profiles. Equation 4 shows the chemical reaction in one kind
of lithium cell.
Unfortunately, the same feature that makes lithium attractive for use in
batteries--its high electrochemical potential--also can cause serious
difficulties in the manufacture and use of such batteries. Many of the
inorganic components of the battery and its casing are destroyed by the
lithium ions and, on contact with water, lithium will react to create
hydrogen which can ignite or can create excess pressure in the cell. Many
fire extinguishers are water based and will cause disastrous results if used
on lithium products. Special D-class fire extinguishers must be used when
lithium is known to be within the boundaries of a fire.[7]
Lithium also has a relatively low melting temperature for a metal, 180
degrees C (356 degrees F). If the lithium melts, it may come into direct
contact with the cathode, causing violent chemical reactions.
Because of the potentially violent nature of lithium, the Department of
Transportation (DOT) has special guidelines for the transport and handling
of lithium batteries. Contact them to ask for DOT Regulations 49 CFR.
Some manufacturers are having success with lithium-iron sulfide,
lithium-manganese dioxide, lithium-carbon monoflouride, lithium-cobalt
oxide, and lithium-thionyl cells.
In recognition of the potential hazards of lithium components,
manufacturers of lithium-based batteries have taken significant steps to
add safety features to the batteries to ensure their safe use.
Lithium primary batteries (in small sizes, for safety reasons) are currently
being marketed for use in flash cameras and computer memory. Lithium
batteries can last three times longer than alkaline batteries of the same
size.[8] But, since the cost of lithium batteries can be three times that of
alkaline batteries, the cost benefits of using lithium batteries are marginal.
Button-size lithium batteries are becoming popular for use in computer
memory back-up, in calculators, and in watches. In applications such as
these, where changing the battery is difficult, the longer lifetime of the
lithium battery makes it a desirable choice.
One company now produces secondary lithium-ion batteries with a voltage
of 3.7 V, "four times the energy density of Ni-Cd batteries," "one-fifth the
weight of Ni-Cd batteries," and can be recharged 500 times.[9]
In general, secondary (rechargeable) lithium-ion batteries have a good
high-power performance, an excellent shelf life, and a better life span than
Ni-Cd batteries. Unfortunately, they have a very high initial cost and the
total energy available per usage cycle is somewhat less than Ni-Cd
batteries.
2.4. Specialty Batteries ("Button" and Miniature Batteries)
"Button" batteries are the nickname given to the category of batteries that
are small and shaped like a coin or a button. They are typically used for
small devices such as cameras, calculators, and electronic watches.
Miniature batteries are very small batteries that can be custom built for
devices, such as hearing aids and electronic "bugs," where even button
batteries can be too large. Industry standardization has resulted in five to
ten standard types of miniature batteries that are used throughout the
hearing-aid industry.
Together, button batteries and miniature batteries are referred to as
specialty batteries.
Most button and miniature batteries need a very high energy density to
compensate for their small size. The high energy density is achieved by
the use of highly electropositive--and expensive--metals such as silver or
mercury. These metals are not cost effective enough to be used in larger
batteries.
Several compositions of specialty batteries are described in the following
sections.
2.4.1. Metal-Air Cells
A very practical way to obtain high energy density in a galvanic cell is to
utilize the oxygen in air as a "liquid" cathode. A metal, such as zinc or
aluminum, is used as the anode. The oxygen cathode is reduced in a
portion of the cell that is physically isolated from the anode. By using a
gaseous cathode, more room is available for the anode and electrolyte, so
the cell size can be very small while providing good energy output. Small
metal-air cells are available for applications such as hearing aids, watches,
and clandestine listening devices.
Metal-air cells have some technical drawbacks, however. It is difficult to
build and maintain a cell where the oxygen acting as the cathode is
completely isolated from the anode. Also, since the electrolyte is in direct
contact with air, approximately one to three months after it is activated,
the electrolyte will become too dry to allow the chemical reaction to
continue. To prevent premature drying of the cells, a seal is installed on
each cell at the time of manufacture. This seal must be removed by the
customer prior to first use of the cell. Alternately, the manufacturer can
provide the battery in an air-tight package.
2.4.2. Silver Oxide
Silver oxide cells use silver oxide as the cathode, zinc as the anode, and
potassium hydroxide as the electrolyte. Silver oxide cells have a
moderately high energy density and a relatively flat voltage profile. As a
result, they can be readily used to create specialty batteries. Silver oxide
cells can provide higher currents for longer periods than most other
specialty batteries, such as those designed from metal-air technology. Due
to the high cost of silver, silver oxide technology is currently limited to
use in specialty batteries.
2.4.3. Mercury Oxide
Mercury oxide cells are constructed with a zinc anode, a mercury oxide
cathode, and potassium hydroxide or sodium hydroxide as the electrolyte.
Mercury oxide cells have a high energy density and flat voltage profile
resembling the energy density and voltage profile of silver oxide cells.
These mercury oxide cells are also ideal for producing specialty batteries.
The component, mercury, unfortunately, is relatively expensive and its
disposal creates environmental problems.
2.5. Other Batteries
This section describes battery technology that is not mature enough to be
available off-the- shelf, has special usage limitations, or is otherwise
impractical for general use.
2.5.1. Nickel-Hydrogen (Ni-H)
Nickel-hydrogen cells were developed for the U.S. space program. Under
certain pressures and temperatures, hydrogen (which is, surprisingly,
classified as an alkali metal) can be used as an active electrode opposite
nickel. Although these cells use an environmentally attractive technology,
the relatively narrow range of conditions under which they can be used,
combined with the unfortunate volatility of hydrogen, limits the
long-range prospects of these cells for terrestrial uses.
2.5.2. Thermal Batteries
A thermal battery is a high-temperature, molten-salt primary battery. At
ambient temperatures, the electrolyte is a solid, non-conducting inorganic
salt. When power is required from the battery, an internal pyrotechnic heat
source is ignited to melt the solid electrolyte, thus allowing electricity to
be generated electrochemically for periods from a few seconds to an hour.
Thermal batteries are completely inert until the electrolyte is melted and,
therefore, have an excellent shelf life, require no maintenance, and can
tolerate physical abuse (such as vibrations or shocks) between uses.
Thermal batteries can generate voltages of 1.5 V to 3.3 V, depending on
the battery's composition. Due to their rugged construction and absence of
maintenance requirements, they are most often used for military
applications such as missiles, torpedoes, and space missions and for
emergency-power situations such as those in aircraft or submarines.
The high operating temperatures and short active lives of thermal batteries
limit their use to military and other large-institution applications.
2.5.3. Super Capacitor
This kind of battery uses no chemical reaction at all. Instead, a special
kind of carbon (carbon aerogel), with a large molecular surface area, is
used to create a capacitor that can hold a large amount of electrostatic
energy.[10] This energy can be released very quickly, providing a specific
energy of up to 4000 Watt-hours per kilogram (Wh/kg), or it can be
regulated to provide smaller currents typical of many commercial devices
such as flashlights, radios, and toys. Because there are no chemical
reactions, the battery can be recharged hundreds of thousands of times
without degradation. Other potential advantages of this kind of cell are its
low cost and wide temperature range. One disadvantage, however, is its
high self-discharge rate. The voltage of some prototypes is approximately
2.5 V.
2.5.4. The Potato Battery
One interesting science experiment involves sticking finger-length pieces
of copper and zinc wire, one at a time, into a raw potato to create a battery.
The wires will carry a very weak current which can be used to power a
small electrical device such as a digital clock.
One vendor sells a novelty digital watch that is powered by a potato
battery. The wearer must put a fresh slice of potato in the watch every few
days.
2.5.5. The Sea Battery
Another interesting battery design uses a rigid framework, containing the
anode and cathode, which is immersed into the ocean to use sea water as
the electrolyte. This configuration seems promising as an emergency
battery for marine use.
2.5.6. Other Developments
Scientists are continually working on new combinations of materials for
use in batteries, as well as new manufacturing methods to extract more
energy from existing configurations.
-------------------------------
3. PERFORMANCE, ECONOMICS AND TRADEOFFS
3.1. Energy Densities
The energy density of a battery is a measure of how much energy the
battery can supply relative to its weight or volume. A battery with an
energy density twice that of another battery should, theoretically, have an
active lifetime twice as long.
The energy density of a battery is mainly dependent on the composition of
its active components. A chemist can use mathematical equations to
determine the theoretical maximum voltage and current of a proposed cell,
if the chemical composition of the anode, cathode, and electrolyte of the
cell are all known. Various physical attributes, such as purity of the
reactants and the particulars of the manufacturing process can cause the
measured voltage, current, and capacity to be lower than their theoretical
values.
3.2. Energy per Mass
Figure 2 compares the gravimetric energy densities of various dry cell
systems discharged at a constant rate for temperatures between -40 degrees
C (-40 degrees F) and 60 degrees C (140 degrees F).
Of the systems shown, the zinc-air cell produces the highest gravimetric
energy density. Basic zinc-carbon cells have the lowest gravimetric energy
density.
3.3. Energy Per Volume
Figure 3 compares the volumetric energy densities of various dry cell
systems discharged at a constant rate for temperatures between -40 degrees
C (-40 degrees F) and 60 degrees C (140 degrees F).
Of the systems shown, the zinc-air cell produces the highest volumetric
energy density. Basic zinc-carbon cells have the lowest volumetric energy
density. The curves for secondary battery cells are not shown in the tables.
Of the major types of secondary cells, Ni-Cd batteries and wet-cell
lead-acid batteries have approximately the same volumetric energy
density. Ni-MH batteries have approximately twice the volumetric energy
density of Ni-Cd batteries.
3.4. Memory Effects
As a rechargeable battery is used, recharged, and used again, it loses a
small amount of its overall capacity. This loss is to be expected in all
secondary batteries as the active components become irreversibly
consumed.
Ni-Cd batteries, however, suffer an additional problem, called the memory
effect. If a Ni-Cd battery is only partially discharged before recharging it,
and this happens several times in a row, the amount of energy available for
the next cycle will only be slightly greater than the amount of energy
discharged in the cell's most-recent cycle. This characteristic makes it
appear as if the battery is "remembering" how much energy is needed for a
repeated application.
The physical process that causes the memory effect is the formation of
potassium-hydroxide crystals inside the cells. This build up of crystals
interferes with the chemical process of generating electrons during the
next battery-use cycle. These crystals can form as a result of repeated
partial discharge or as a result of overcharging the Ni-Cd battery.
The build up of potassium-hydroxide crystals can be reduced by
periodically reconditioning the battery. Reconditioning of a Ni-Cd battery
is accomplished by carefully controlled power cycling (i.e., deeply
discharging and then recharging the battery several times). This power
cycling will cause most of the crystals to redissolve back into the
electrolyte. Several companies offer this reconditioning service, although
battery users can purchase a reconditioner and recondition their own
batteries. Some batteries can be reconditioned without a special
reconditioner by completely draining the battery (using the battery
powered device itself or a resistive circuit designed to safely discharge the
battery) and charging it as normal.
3.5. Voltage Profiles
The voltage profile of a battery is the relation- ship of its voltage to the
length of time it has been discharging (or charging). In most primary
batteries, the voltage will drop steadily as the chemical reactions in the cell
are diminished. This diminution leads to an almost-linear drop in voltage,
called a sloping profile. Batteries with sloping voltage profiles provide
power that is adequate for many applications such as flashlights, flash
cameras, and portable radios.
Ni-Cd batteries provide a relatively flat voltage profile. The cell's voltage
will remain relatively constant for more than two-thirds of its discharge
cycle. At some point near the end of the cycle, the voltage drops sharply to
nearly zero volts. Batteries with this kind of profile are used for devices
that require a relatively steady operating voltage.
One disadvantage of using batteries with a flat voltage profile is that the
batteries will need to be replaced almost immediately after a drop in
voltage is noticed. If they are not immediately replaced, the batteries will
quickly cease to provide any useful energy.
Figure 4 shows the conceptual difference between a flat discharge rate and
a sloping discharge rate.
Figure 5 (Sec. 5) shows actual voltage profiles for several common battery
types.
3.6. Self-Discharge Rates
All charged batteries (except thermal batteries and other batteries
specifically designed for a near-infinite shelf life) will slowly lose their
charge over time, even if they are not connected to a device. Moisture in
the air and the slight conductivity of the battery housing will serve as a
path for electrons to travel to the cathode, discharging the battery. The rate
at which a battery loses power in this way is called the self-discharge rate.
Ni-Cd batteries have a self-discharge rate of approximately 1% per day.
Ni-MH batteries have a much higher self-discharge rate of approximately
2% to 3% per day. These high discharge rates require that any such
battery, which has been stored for more than a month, be charged before
use.
Primary and secondary alkaline batteries have a self-discharge rate of
approximately 5% to 10% per year, meaning that such batteries can have a
useful shelf life of several years. Lithium batteries have a self-discharge
rate of approximately 5% per month.
3.7. Operating Temperatures
As a general rule, battery performance deteriorates gradually with a rise in
temperature above 25 degrees C (77 degrees F), and performance
deteriorates rapidly at temperatures above 55 degrees C (131 degrees F).
At very low temperatures -20 degrees C (-4 degrees F) to 0 degree C (32
degrees F), battery performance is only a fraction of that at 25 degrees C
(77 degrees F). Figure 2 and Figure 3 show the differences in energy
density as a function of temperature.
At low temperatures, the loss of energy capacity is due to the reduced rate
of chemical reactions and the increased internal resistance of the
electrolyte. At high temperatures, the loss of energy capacity is due to the
increase of unwanted, parasitic chemical reactions in the electrolyte.
Ni-Cd batteries have a recommended temperature range of +17 degrees C
(62 degrees F) to 37 degrees C (98 degrees F). Ni-MH have a
recommended temperature range of 0 degree C (32 degrees F) to 32
degrees C (89 degrees F).
3.8. Cycle Life
The cycle life of a battery is the number of discharge/recharge cycles the
battery can sustain, with normal care and usage patterns, before it can no
longer hold a useful amount of charge.
Ni-Cd batteries should have a normal cycle life of 600 to 900 recharge
cycles. Ni-MH batteries will have a cycle life of only 300 to 400 recharge
cycles. As with all rechargeable batteries, overcharging a Ni-Cd or Ni-MH
battery will significantly reduce the number of cycles it can sustain.
3.9. Capacity Testing
Many battery manufacturers recommend the constant-load test to
determine the capacity of a battery. This test is conducted by connecting a
predetermined load to the battery and then recording the amount of time
needed to discharge the battery to a predetermined level.
Another recommended test is the intermittent-or switching-load test. In
this type of test, a predetermined load is applied to the battery for a
specified period and then removed for another period. This load
application and removal is repeated until the battery reaches a
predetermined level of discharge. This kind of test simulates the battery
usage of a portable radio.
A comparison of these two kinds of tests was performed on five
commonly available types of batteries.[11] The data shows that the five
tested batteries all had a constant-load duration of 60 to 80 minutes, which
indicates that the five batteries had similar capacities.
But, intermittent-load testing of those same five batteries showed that the
duration of the batteries ranged from 8.5 hours to 12 hours. There was no
correlation of the results of the two tests, meaning that batteries that
performed best under constant-load testing did not necessarily perform
well under intermittent-load testing. The study concluded that the ability
of a battery to recover itself between heavy current drains cannot be made
apparent through a constant-load test.
3.10. Battery Technology Comparison
Table 3 shows a comparison of some of the performance factors of several
common battery types.
The initial capacity of a battery refers to the electrical output, expressed in
ampere-hours, which the fresh, fully charged battery can deliver to a
specified load. The rated capacity is a designation of the total electrical
output of the battery at typical discharge rates; e.g., for each minute of
radio transceiver operation, 6 seconds shall be under a transmit current
drain, 6 seconds shall be under a receive current drain and 48 seconds shall
be under a standby current drain.
-------------------------------
Table 3. Battery Technology Comparison (adapted from Design Note:
Renewable Reusable Alkaline Batteries)
(See Sec. 3.10)
Secondary Alkaline:
Initial Capacity = 2; Rated Capacity = 4; Self-Discharge = 1; Cycle Life =
2; Initial Cost* = 2; Life-Cycle Cost* = 2
Primary Alkaline:
Initial Capacity = 1; Rated Capacity = 3; Self-Discharge = 1; Cycle Life =
4; Initial Cost* = 1; Life-Cycle Cost* = 4
Ni-Cd:
Initial Capacity = 4; Rated Capacity = 1; Self-Discharge = 3; Cycle Life =
1; Initial Cost* = 3; Life-Cycle Cost* = 2
Ni-MH:
Initial Capacity = 3; Rated Capacity = 2; Self-Discharge = 4; Cycle Life =
1; Initial Cost* = 4; Life-Cycle Cost* = 2
Worst Performance = 4, Low Performance = 3, Good Performance= 2,
Best Performance = 1 *A better performance ranking means lower costs.
-------------------------------
The self-discharge rate is the rate at which the battery will lose its charge
during storage or other periods of non-use. The cycle life is the number of
times that the rechargeable battery can be charged and discharged before it
becomes no longer able to hold or deliver any useful amount of energy.
The initial cost is the relative cost of purchasing the battery. The life-cycle
cost is the per-use relative cost of the battery.
Table 4 shows a more detailed comparison of many of the available
battery types.
-------------------------------
4. SELECTING THE RIGHT BATTERY FOR THE APPLICATION
Batteries come in many different shapes, sizes, and compositions. There is
no one "ideal" battery that can satisfy all possible requirements equally.
Different battery technologies have been developed that will optimize
certain parameters for specific battery uses.
In general, the energy output of a battery is related only to its size and
material composition. Different battery designs and different
manufacturing methods (for the same type, size, and composition of
battery) will, in general, lead to only minor differences in the batteries'
electrical output. Battery-industry standards have contributed to the fact
that batteries (of the same type, composition, and size) from different
manufacturers are quite interchangeable.
However, the small differences that do exist between batteries made by
different manufacturers, can be significant when using a multi-cell array of
matched cells. In these cases, potential replacement cells must be graded
to see if the cells properly match the capacity of the existing cells.
Even for non-matched, multi-cell applications, such as flashlights, portable
radios, etc., it is still a good rule of thumb to avoid mixing batteries from
different manufacturers within one device. Small variances in voltage and
current, between different brands of battery, can slightly shorten the useful
life span of all of the batteries.
Do not mix batteries of different types (e.g., do not mix rechargeable
alkaline batteries with Ni- Cd batteries) within a single device or within an
array of batteries.
Figure 5 shows some discharge curves for several popular AA size battery
types. Two of the curves (secondary alkaline [1st use] and [25th use])
show that secondary alkaline batteries rapidly lose their capacity as they
are used and recharged. Only one Ni-Cd curve is shown, since its curve
remains essentially the same throughout most its life span.
4.1. Battery Properties
Battery applications vary, as do considerations for selecting the correct
battery for each application. Some of the important factors that customers
might consider when selecting the right battery for a particular application
are listed below:
-- Chemistry -- Which kind of battery chemistry is best for the
application? Different chemistries will generate different voltages and
currents.
-- Primary or Secondary -- Primary batteries are most appropriate for
applications where infrequent, high-energy output is required. Secondary
batteries are most appropriate for use in devices that see steady periods of
use and non-use (pagers, cellular phones, etc.).
-- Standardization and Availability -- Is there an existing battery design
that meets the application needs? Will replacement batteries be available
in the future? Using existing battery types is almost always preferable to
specifying a custom-made battery design.
-- Flexibility -- Can the battery provide high or low currents over a wide
range of conditions?
-- Temperature Range -- Can the battery provide adequate power over the
expected temperature range for the application?
-- Good Cycle Life -- How many times can the rechargeable battery be
discharged and recharged before it becomes unusable?
-- Costs -- How expensive is the battery to purchase? Does the battery
require special handling?
-- Shelf Life -- How long can the battery be stored without loss of a
significant amount of its power?
-- Voltage -- What is the voltage of the battery? (Most galvanic cells
produce voltages of between 1.0 and 2.0 V.)
-- Safety -- Battery components range from inert, to mildly corrosive, to
highly toxic or flammable. The more hazardous components will require
additional safety procedures.
-- Hidden Costs -- Simpler manufacturing processes result in lower cost
batteries. However, if a battery contains toxic or hazardous components,
extra costs will be incurred to dispose of the battery safely after its use.
Table 5 shows a short list of different battery types and the kinds of
application that are appropriate for each.
4.2. Environmental Concerns
All battery components, when discarded, contribute to the pollution of the
environment. Some of the components, such as paperboard and carbon
powder, are relatively organic and can quickly merge into the ecosystem
without noticeable impact. Other components, such as steel, nickel, and
plastics, while not actively toxic to the ecosystem, will add to the volume
of a landfill, since they decompose slowly.
-------------------------------
Table 5. Recommended Battery Types for Various Usage Conditions
Battery Type: Primary Alkaline
Device Drain Rate: High
Device Use Frequency: Moderate
Battery Type: Secondary Alkaline
Device Drain Rate: Moderate
Device Use Frequency: Moderate
Battery Type: Primary Lithium
Device Drain Rate: High
Device Use Frequency: Frequent
Battery Type: Secondary Ni-Cd
Device Drain Rate: High
Device Use Frequency: Frequent
Battery Type: Primary Zn-C ("Heavy Duty")
Device Drain Rate: Moderate
Device Use Frequency: Regular
Battery Type: Primary Zn-C ("Standard")
Device Drain Rate: Low
Device Use Frequency: Occasional
-------------------------------
Of most concern, however, are the heavy-metal battery components,
which, when discarded, can be toxic to plants, animals, and humans.
Cadmium, lead, and mercury are the heavy-metal components most likely
to be the target of environmental concerns.
Several of the major battery manufacturers have taken steps to reduce the
amount of toxic materials in their batteries. One manufacturer reports the
reduction of the mercury content of their most-popular battery from
0.75%, in 1980, to 0.00%, in 1996.[12] Other manufacturers report that
their current battery formulas contain no mercury. The U.S. Department of
Mines, in 1994, estimated that, for the U.S. production of household
batteries, mercury usage had fallen from 778 tons in 1984 to (a projected)
10 tons in 1995.[13]
Many of the major battery manufacturers have put significant efforts into
the recycling of discarded batteries. According to one manufacturer, it
takes six to ten times more energy to recycle a battery than to create the
battery components from virgin materials. Efforts are underway that could
improve the recycling technology to make recycling batteries much more
energy efficient and cost effective.[14]
The use of secondary (rechargeable) batteries is more cost efficient than
the use of primary batteries. Such use will reduce the physical volume of
discarded batteries in landfills, because the batteries can be recharged and
reused 25 to 1000 times before they must be discarded.
The most popular secondary batteries, however, contain cadmium. Many
manufacturers, responding to customer requests and legislative demands,
are designing nickel-metal hydride, lithium-ion, and rechargeable-alkaline
secondary batteries that contain only trace amounts of cadmium, lead, or
mercury.
4.3. Standardization
Existing off-the-shelf batteries are often preferred to batteries that require
special design and manufacturing. Some benefits of using off-the-shelf
batteries are listed below:
-- The use of a proven design can reduce the risk of the battery not
working properly.
-- The use of tested technology eliminates costly and time-consuming
development efforts.
-- The use of a proven design reduces unit production costs because of
competitive, multi-source availability.
-- The use of tested technology reduces operations and support costs
through commonality of training, documentation, and replacement efforts.
4.4. Testing Capacities
One method of estimating battery capacity requirements for a specific
battery-powered device is to calculate the current drawn during the typical
duty cycle for the device.
Standard duty cycles for battery service life and capacity determinations
are defined in EIA/TIA Standard 603 for land mobile radio
communications[15] and NIJ Standard-0211.01 for hand- held portable
radio applications.[16] Specifically, in an average 1 minute period of
mobile-radio usage, 6 seconds (10%) is spent receiving, 6 seconds (10%)
is spent transmitting and 48 seconds (80%) is spent in the idle mode. Table
8 provides an example of a transceiver drawing an average current of 8.0 +
6.2 + 32.5 = 46.7 mA. For a typical duty cycle composed of 8 hours of
operation (followed by 16 hours of rest) a minimum battery capacity of
374 mAh is required. One manufacturer of portable communications
equipment recommends that batteries be replaced if they fail to deliver
80% or more of their original rated capacity. Below 80% batteries are
usually found to deteriorate quickly. Because a minimum requirement of
374 mAh is 75% of the rated capacity of a 500 mAh battery, the latter
should adequately provide power for the entire duty described.[17]
-------------------------------
Table 6. Typical Usage of Portable Telecommunications Equipment.
Standby Mode
Percent of Duty Cycle: 80% (48 minutes of each hour)
Current Drain for Mode: 10 mA
Average Current for Mode: 8.0 mA
Receive Mode
Percent of Duty Cycle: 10% (6 minutes of each hour)
Current Drain for Mode: 62 mA
Average Current for Mode: 6.2 mA
Transmit Mode
Percent of Duty Cycle: 10% (6 minutes of each hour)
Current Drain for Mode: 325 mA
Average Current for Mode: 32.5 mA
-------------------------------
Similar calculations can be performed for any battery in any
battery-powered device by using the data relevant to the device and the
proposed battery. The manufacturers should either provide such
appropriate information with the batteries and devices, or they should be
able to provide those data on request.
4.5. Mobile Radios
As reported above, mobile radios have a typical duty cycle of 10%
transmit, 10% receive, and 80% standby. The maximum current drain will
occur during the transmit cycle. Each radio, typically, will have a daily
cycle of 8 hours of use and 16 hours of non-use. The non-use hours may
be used to charge the radio's batteries.
Most commercial, off-the-shelf mobile-radio units include a battery. But,
since many radio units are in service 7 days a week, 52 weeks a year, and
since the batteries are discharged and recharged daily, each set of batteries
should wear out approximately once every two years (~700 recharge
cycles). Replacement batteries should be purchased as directed by the user
manual for the unit.
4.6. Cellular Phones and PCS Phones
Most commercial, off-the-shelf cellular phones contain a battery when
purchased. Charging units may be supplied with the phone or may be
purchased separately.
Typical usage for cellular telephones will vary significantly with user, but,
the estimate for mobile radio usage (10% of the duty cycle is spent in
transmit mode, 10% in receive mode, and 80% in standby mode) is also a
reasonable estimate for cellular phone usage. At the end of each usage
cycle, the user places the battery (phone) on a recharging unit that will
charge the battery for the next usage cycle. This usage pattern is
appropriate for Ni-Cd or Ni-MH batteries. Ni-Cd batteries should be
completely discharged between uses to prevent memory effects created by
a recurring duty cycle.
When a replacement or spare battery is needed, only replacements,
recommended by the phone manufacturer should be used.
Batteries and battery systems from other manufacturers may be used if the
batteries are certified to work with that particular brand and model of
phone. Damage to the phone may result if non- certified batteries are used.
Several battery manufacturers make replacement battery packs that are
designed to work with a wide variety of cellular phones. Because of the
variety of phones available, battery manufacturers must design and sell
several dozen different types of batteries to fit the hundreds of models of
cellular phones from dozens of different manufacturers.[18] The user is
advised to check battery interoperability charts before purchasing a
replacement battery.
One battery manufacturer offers a battery replacement system that allows a
phone owner to use household primary batteries, inserted into a special
housing (called a refillable battery pack), to replace the phone's regular
rechargeable battery pack. This refillable pack, says the manufacturer, is
designed for light-use customers, who require that their phone's batteries
have the long shelf life of primary batteries. This refillable pack can also
be used in emergencies, for example, where the phone's rechargeable
battery pack is exhausted and no recharged packs are available. Primary
household batteries can be readily purchased (or borrowed from other
devices), inserted into the refillable pack, and used to power the
phone.[19]
4.7. Laptop Computers
Most commercial, off-the-shelf laptop computers have a built-in battery
system. In addition to the battery provided, most laptops will have a
battery adapter that also serves as a battery charger.
The expected usage of a laptop computer is that the operator will use it
several times a week, for periods of several hours at a time. The computer
will drain the battery at a moderate rate when the computer is running, and
at the self-discharge rate when the computer is shut off. Quite often, the
user will use the computer until the "low battery" alarm sounds. At this
point, the battery will be drained of 90% of its charge before the user
recharges it. The computer will also register regular periods of non-use,
during which the battery can be recharged. Secondary Ni-Cd batteries are
most appropriate for this usage pattern.
When a laptop-computer battery reaches the end of its life cycle, it should
be replaced with a battery designed specifically for that laptop computer.
Using other types of batteries may damage the computer. The user's
manual for the laptop computer will list one or more battery types and
brands that may be used. If in doubt, the user is advised to contact the
manufacturer of the laptop computer and ask for a battery-replacement
recommendation.
4.8. Camcorders
Almost all commercial, off-the-shelf camcorders come with a battery and
a recharging unit when purchased.
The camcorder is typically operated continuously for several minutes or
hours (to produce a video recording of some event). This use will require
that the battery provide approximately 2 hours of non-stop recording time.
The electric motor driving the recording tape through the camcorder
requires a moderately high amount of power throughout the entire
recording period.
Rechargeable Ni-Cd or Ni-MH batteries or primary lithium batteries are
usually the only choice for camcorder use. Several battery manufacturers
produce Ni-Cd or Ni-MH batteries that are specially designed for use in
camcorders. Due to the lack of sufficient standardization for these kind of
batteries, the battery manufacturers must design and sell approximately 20
different camcorder batteries to fit at least 100 models of camcorders from
over a dozen manufacturers.[20]
Camcorder batteries are usually designed to provide 2 hours of service, but
larger batteries are available that can provide up to 4 hours of service.
Lithium camcorder batteries can provide three to five times the energy of a
single cycle of secondary Ni-Cd batteries. These lithium batteries,
however, are primary batteries and must be properly disposed of at the end
of their life cycle. Secondary lithium-ion camcorder batteries are being
developed.
4.9. Summary
There are six varieties of batteries in use, each with its own advantages
and disadvantages. Below is a short summary of each variety:
-- Lead-Acid -- Secondary lead-acid batteries are the most popular
worldwide. Both the battery product and the manufacturing process are
proven, economical, and reliable.
-- Nickel-Cadmium -- Secondary Ni-Cd batteries are rugged and reliable.
They exhibit a high- power capability, a wide operating temperature range,
and a long cycle life. They have a self- discharge rate of approximately 1%
per day.
-- Alkaline -- The most commonly used primary cell (household) is the
zinc-alkaline manganese dioxide battery. They provide more
power-per-use than secondary batteries and have an excellent shelf life.
-- Rechargeable Alkaline -- Secondary alkaline batteries have a long shelf
life and are useful for moderate-power applications. Their cycle life is less
than most other secondary batteries.
-- Lithium Cells -- Lithium batteries offer performance advantages well
beyond the capabilities of conventional aqueous electrolyte battery
systems. However, lithium batteries are not widely used because of safety
concerns.
-- Thermal Batteries -- These are special batteries that are capable of
providing very high rates of discharge for short periods of time. They have
an extremely long shelf life, but, because of the molten electrolyte and
high operating temperature, are impractical for most household uses.
-------------------------------
5. BATTERY HANDLING AND MAINTENANCE
The following guidelines offer specific advice on battery handling and
maintenance. This advice is necessarily not all inclusive. Users are
cautioned to observe specific warnings on individual battery labels and to
use common sense when handling batteries.
5.1. Battery Dangers
-- To get help, should someone swallow a battery, immediately call The
National Battery Ingestion Hot Line collect at (202) 625-3333. Or, call
911 or a state/local Poison Control Center.
-- Batteries made from lead (or other heavy metals) can be very large and
heavy and can cause damage to equipment or injuries to personnel if
improperly handled.
-- When using lithium batteries, a "Lith-X" or D-Class fire extinguisher
should always be available. Water-based extinguishers must not be used
on lithium of any kind, since water will react with lithium and release
large amounts of explosive hydrogen.
-- Before abusively testing a battery, contact the manufacturer of the
battery to identify any potential dangers.
-- Vented batteries must be properly ventilated. Inadequate ventilation may
result in the build up of volatile gases, which may result in an explosion or
asphyxiation.
-- Do not attempt to solder directly onto a terminal of the battery.
Attempting to do so can damage the seal or the safety vent.
-- When disconnecting a battery from the device it is powering,
disconnect one terminal at a time. If possible, first remove the ground
strap at its connection with the device's framework. Observing this
sequence can prevent an accidental short circuit and also avoid risking a
spark at the battery. In most late-model, domestic automobiles, the battery
terminal labeled "negative" is usually connected to the automobile's
framework.
-- Do not attempt to recharge primary batteries. This kind of battery is not
designed to be recharged and may overheat or leak if recharging is
attempted.
-- When recharging secondary batteries, use a charging device that is
approved for that type of battery. Using an approved charging device can
prevent overcharging or overheating the battery. Many chargers have
special circuits built into them for correctly charging specific types of
batteries and will not work properly with other types.
-- Do not use secondary (rechargeable) batteries in smoke detectors.
Secondary batteries have a high self-discharge rate. Primary batteries have
a much longer shelf life and are much more dependable in emergencies.
Consult the smoke detector's user manual for the recommended battery
types.
-- Do not attempt to refill or repair a worn-out or damaged battery.
-- Do not allow direct bodily contact with battery components. Acidic or
alkaline electrolyte can cause skin irritation or burns. Electrode materials
such as mercury or cadmium are toxic. Lithium can cause an explosion if
it comes into contact with water. Other components can cause a variety of
short-term (irritation and burns) or long-term (nerve damage) maladies.
-- Do not lick a 9 V battery to see if it is charged. You will, of course, be
able to determine whether or not the battery is charged, but such a test may
result in a burn that may range from simply uncomfortable to serious.
-- Do not dispose of batteries in a fire. The metallic components of the
battery will not burn and the burning electrolyte may splatter, explode, or
release toxic fumes. Batteries may be disposed of, however, in industrial
incinerators that are approved for the disposal of batteries.
-- Do not carry batteries in your pocket. Coins, keys, or other metal
objects can short circuit a battery, which can cause extreme heat, acid
leakage, or an explosion.
-- Do not wear rings, metal jewelry, or metal watchbands while handling
charged cells. Severe burns can result from accidentally short circuiting a
charged cell. Wearing gloves can reduce this danger.
-- Do not use uninsulated tools near charged cells. Do not place charged
cells on metal workbenches. Severe arcing and overheating can result if
the battery's terminals are shorted by contact with such metal objects.
-------------------------------
The Straight Dope
by Cecil Adams, The Chicago Reader
Is it true that refrigerating batteries will extend shelf life? If so, why does a
cold car battery cause slower starts? The answer will help me sleep better.
-- Kevin C., Alexandria, Virginia
Whatever it takes, dude. Refrigerating batteries extends shelf life because
batteries produce electricity through a chemical reaction. Heat speeds up
any reaction, while cold slows it down. Freeze your [car battery] and you'll
extend its life because the juice won't leak away--but it'll also make those
volts a little tough to use right away. That accounts for the belief
occasionally voiced by mechanics that if a battery is left on the garage
floor for an extended period, the concrete will "suck out the electricity." It
does nothing of the kind, but a cold floor will substantially reduce a
battery's output. The cure: warm it up first.
(Reprinted, with permission, from Return of the Straight Dope. [copyright]
1994 Chicago Reader, Inc.)
-------------------------------
5.2. Extending Battery Life
-- Read the instructions for the device before installing batteries. Be sure
to orient the battery's positive and negative terminals correctly when
inserting them.
-- In a device, use only the type of battery that is recommended by the
manufacturer of the device.
-- To find a replacement battery that works with a given device, call the
manufacturer of the device or ask the retailer to check the manufacturer's
battery cross-reference guide.
-- Store batteries in a cool, dark place. This helps extend their shelf life.
Refrigerators are convenient locations. Although some battery
manufacturers say that refrigeration has no positive effect on battery life,
they say it has no negative effect either. Do not store batteries in a freezer.
Always let batteries come to room temperature before using them.
-- Store batteries in their original boxes or packaging materials. The
battery manufacturer has designed the packaging for maximum shelf life.
-- When storing batteries, remove any load or short circuit from their
terminals.
-- When storing battery-powered devices for long periods (i.e., more than a
month), remove the batteries. This can prevent damage to the device from
possible battery leakage. Also, the batteries can be used for other
applications while the batteries are still "fresh."
-- Use a marking pen to indicate, on the battery casing, the day and year
that the battery was purchased. Also, keep track of the number of times the
battery has been recharged. Avoid writing on or near the battery terminals.
-- Do not mix batteries from different manufacturers in a multi-cell device
(e.g., a flashlight). Small differences in voltage, current, and capacity,
between brands, can reduce the average useful life of all the batteries.
-- When using secondary batteries in a multi-cell device (e.g., a flashlight),
try to use batteries of the same age and similar charging histories. This
kind of matching will make it more likely that all the batteries will
discharge at the same rate, putting less stress on any individual battery.
-- When using single-cell rechargeable Ni-Cd batteries, be sure to
discharge the cell completely before recharging it, thus counteracting the
"memory" effect.
-- Secondary Ni-Cd batteries can sometimes be reconditioned to reduce the
impact of "memory" effects. Completely discharge the battery and
recharge it several times.
-- Do not use batteries in high-temperature situations (unless the battery is
designed for that temperature range). Locate batteries as far away from
heat sources as possible. The electrical potential of the battery will degrade
rapidly if it is exposed to temperatures higher than those recommended by
the manufacturer.
-------------------------------
6. BATTERY CHARGERS AND ADAPTERS
6.1. Battery Chargers
Secondary (rechargeable) batteries require a battery charger to bring them
back to full power. The charger will provide electricity to the electrodes
(opposite to the direction of electron discharge), which will reverse the
chemical process within the battery, converting the applied electrical
energy into chemical potential energy.
Batteries should only be recharged with chargers that are recommended,
by the manufacturer, for that particular type of battery. In general,
however, battery-industry standards ensure that any off-the-shelf battery
charger, specified for one brand, size, and type of battery, will be able to
charge correctly any brand of battery of that same size and type.
Do not, however, use a charger designed for one type of battery to charge
a different type of battery, even if the sizes are the same. For example, do
not use a charger designed for charging "D"-sized Ni-Cd batteries to
charge "D"-sized rechargeable alkaline batteries. If in doubt, use only the
exact charger recommended by the battery manufacturer.
Recharging a battery without a recommended charger is dangerous. If too
much current is supplied, the battery may overheat, leak, or explode. If not
enough current is applied, the battery may never become fully charged,
since the self-discharge rate of the battery will nullify the charging effort.
It is not recommended that battery users design and build their own
charging units. Many low- cost chargers are available off-the-shelf that do
a good job of recharging batteries. Specific, off- the-shelf chargers are
identified and recommended, by each of the major battery manufacturers,
for each type of secondary battery they produce.
6.2. Charge Rates
The current that a charger supplies to the battery is normally expressed as
a fraction of the theoretical current (for a given battery) needed to charge
the battery completely in 1 hour. This theoretical current is called the
nominal battery capacity rating and is represented as "C." For example, a
current of 0.1 C is that current which, in 10 hours, theoretically, would
recharge the battery fully. Table 7 shows some common charging rates for
various styles of recharging.
-------------------------------
Table 7. Charge Rate Descriptions
Charge Rate (Amperes) Description
Standby (Trickle): 0.01 C to 0.03 C
Slow (Overnight): 0.05 C to 0.1 C
Quick: 0.2 C to 0.5 C
Fast: 1 C and more
Nominal Charge Time (Hours) Description
Standby (Trickle): 100 to 33
Slow (Overnight): 20 to 10
Quick: 5 to 2
Fast: 1 and less
"C" is the theoretical current needed to completely charge the fully
discharged battery in one hour.
-------------------------------
6.3. Charging Techniques
In general, lower charge rates will extend the overall life of the battery. A
battery can be damaged or degraded if too much current is applied during
the charging process. Also, when a battery is in the final stages of
charging, the current must be reduced to prevent damage to the battery.
Many chargers offer current-limiting devices that will shut off or reduce
the applied current when the battery reaches a certain percent of its
charged potential.
Slow charge rates (between 0.05 C and 0.1 C) are the most-often
recommended charge rate, since a battery can be recharged in less than a
day, without significant probability of damaging or degrading the battery.
Slow charge rates can be applied to a battery for an indefinite period of
time, meaning that the battery can be connected to the charger for days or
weeks with no need for special shut-off or current-limiting equipment on
the charger.
Trickle chargers (charge rates lower than 0.05 C) are generally insufficient
to charge a battery. They are usually only applied after a battery is fully
charged (using a greater charge rate) to help offset the self-discharge rate
of the battery. Batteries on a trickle charger will maintain their full charge
for months at a time. It is usually recommended that batteries on a trickle
charger be fully discharged and recharged once every 6 to 12 months.
Quick and fast charging rates (over 0.2 C) can be used to charge many
kinds of secondary batteries. In such cases, however, damage or
deterioration can occur in the battery if these high charge rates are applied
after the battery has approximately 85% of its charge restored. Many quick
and fast chargers will have current-limiters built into them that will slowly
reduce the current as the battery is charged, thereby preventing most of
this deterioration.
The recharge times shown in Table 7 may be somewhat lower than the
actual times required to recharge batteries at the associated charge rates.
Various elements, such as temperature, humidity, initial charge state, and
the recharge history of the cell, will each act to extend the time needed to
charge the cell fully.
6.4. Charging Lead-Acid Batteries
Constant potential charging, with current limiting, is usually
recommended for sealed lead-acid cells. Due to the sloping voltage profile
of a lead-acid battery, the voltage of the battery is a reliable indicator of its
state of charge. Current limiting may be accomplished through the use of a
current-limiting resistor. One manufacturer uses a miniature light bulb as a
current-limiting resistor. The brightness of the bulb will provide a visual
indication of the state of charge of the battery. In modern practice,
however, current limiting is accomplished with integrated circuits.
6.5. Charging Ni-Cd Batteries
During their recharge cycle, nickel-cadmium batteries react in a manner
different from other batteries. Nickel-cadmium batteries will actually
absorb heat during the first 25% of the charge cycle (as opposed to most
secondary batteries, which generate heat all through their recharge cycle).
Beyond that first quarter of the charge cycle, a Ni-Cd battery will generate
heat. If constant current is applied past the point when the battery reaches
approximately 85% of its fully charged state, the excess heat will cause
"thermal runaway" to occur. Under thermal runaway conditions, the excess
heat in the battery will cause its voltage to drop. The drop in voltage will
cause the charge rate to increase (according to Ohm's Law), generating
more heat and accelerating the cycle. The temperature and internal
pressure of the battery will continue to rise until permanent damage
results.
When using trickle or slow chargers to charge Ni-Cd batteries, the heat
build-up is minimal and is normally dissipated by atmospheric convection
before thermal runaway can occur. Most chargers supplied with, or as a
part of, rechargeable devices (sealed flashlights, mini-vacuums, etc.) are
slow chargers.
Quick or fast battery chargers, designed especially for Ni-Cd batteries, will
usually have a temperature sensor or a voltage sensor that can detect when
the battery is nearing thermal- runaway conditions. When near-runaway
conditions are indicated, the charger will reduce or shut off the current
entering the battery.
6.6. Timed-Charge Charging
Most charging methods, described so far in this guide, allow the user to
begin charging a cell regardless of its current state of charge. One
additional method can be used to charge Ni-Cd cells, but only if the cell is
completely discharged. It is called the timed-charged method.
One characteristic of Ni-Cd cells is that they can accept very large charge
rates (as high as 20 C), provided that the cell is not forced into an
overcharge condition.
The timed-charge charger will provide high-rate current to the cell for a
very specific period. A timer will then cut off the charging current at the
end of that period. Some cells can be charged completely in as little as 10
minutes (as opposed to 8 hours on a slow charger).
Great care should be exercised when using a timed-charge charger,
because there is no room for error. If the cell has any charge in it at all at
the beginning of the charge cycle, or if the cell's capacity is less than
anticipated, the cell can quickly reach the fully charged state, proceed into
thermal-runaway conditions, and cause the explosion or destruction of the
cell.
Some timed-charge chargers have a special circuit designed to discharge
the cell completely before charging it. These are called dumped
timed-charge chargers, since they dump any remaining charge before
applying the timed charge.
6.7. Pulsed Charge-Discharge Chargers
This method of charging Ni-Cd cells applies a relatively high charge rate
(approximately 5 C) until the cell reaches a voltage of 1.5 V. The charging
current is then removed and the cell is rapidly discharged for a brief period
of time (usually a few seconds). This action depolarizes the cell
components and dissipates any gaseous buildup within the cell. The cell is
then rapidly charged back to 1.5 V. The process is repeated several more
times until the cell's maximum charge state is reached.
Unfortunately, this method has some difficulties. The greatest difficulty is
that the maximum voltage of a Ni-Cd cell will vary with several outside
factors such as the cell's recharge history and the ambient temperature at
the charger's location. Since the cell's maximum potential voltage is
variable, the level to which it must be charged is also variable. Integrated
circuits are being designed, however, that may compensate for such
variations.
6.8. Charging Button Batteries
Secondary cylindrical (household) cells will usually have a safety seal or
vent built into them to allow excess gases, created during the charging
process, to escape. Secondary, button-type batteries do not have such seals
and are often hermetically sealed.
When cylindrical cells are overcharged, excess gases are vented. If a
button battery is inadvertently overcharged, the excess gases cannot
escape. The pressure will build up and will damage the battery or cause an
explosion. Care should be taken not to overcharge a secondary button
battery.
6.9. Internal Chargers
For some applications, the charger may be provided, by the battery
manufacturer, as an integral part of the battery itself. This design has the
obvious advantage of ensuring that the correct charger is used to charge
the battery, but this battery-charger combination may result in size, weight
and cost penalties for the battery.
6.10. Battery Testers
A battery tester is a device that contains a small load and attaches across
the terminals of a battery to allow the user to see if the battery is
sufficiently charged. A simple battery tester can be made from a flashlight
bulb and two pieces of wire. Flashlight bulbs are ideal for testing
household batteries, since the voltage and current required to light the bulb
is the same as that of the battery. This kind of flashlight-bulb tester can
also be used to drain a secondary battery safely before fully charging it.
Some off-the-shelf household batteries are sold with their own testers.
These testers are attached to the packaging material or to the battery itself.
The active conductor in the tester is covered by a layer of heat-sensitive
ink. As the ends of the tester are pressed against the battery terminals, a
small amount of current will flow through the material under the ink,
heating it. The heating will cause the ink to change color, indicating that
the battery still has energy.
Using a simple battery tester to test a Ni-Cd battery can be somewhat
misleading, since a Ni-Cd battery has a flat voltage profile. The tester will
indicate near-maximum voltage whether the battery is 100% charged or
85% discharged.
6.11. "Smart" Batteries
Many battery-powered devices require the use of multi-cell battery packs
(i.e., several ordinary battery cells strapped together to be used as a single
unit). The individual cells cannot be charged or measured separately,
without destroying the battery pack.
A new development in rechargeable battery technology is the use of
microelectronics in battery- pack cases to create "intelligent" battery
packs. These "smart" battery packs contain a microprocessor, memory,
and sensors that monitor the battery's temperature, voltage, and current.
This information can be relayed to the device (if the device is designed to
accept the information) and used to calculate the battery's state of charge at
any time or to predict how much longer the device can operate. The
microprocessor on a battery pack may also record the history of the battery
and display the dates and number of times that it has been charged.
To get the maximum potential from a secondary battery, the user must
adopt a strict regimen of noting certain information about the battery and
acting upon that information. For example, if a battery is already partially
discharged, using it in a device will obviously not allow the device to be
used for its entire duty cycle. Attempting to charge a battery when the
ambient temperature is too high is another example of suboptimal battery
usage, since the battery will not hold as much charge as it would have had
it been charged at the recommended temperature.
Most battery users are not sufficiently diligent in matters of battery
maintenance. "Smart" batteries allow the battery itself to record all
pertinent information and make it available to the user at a glance.
6.12. End of Life
All secondary batteries will eventually fail due to age, expended
components, or physical damage. A battery, when properly maintained,
will fail through gradual loss of capacity. To the user, this gradual failure
will appear as a frequent need to change and charge the batteries. Sudden
failure, usually due to physical abuse, will prevent the battery from
holding any charge at all.
The physical manifestations of a gradual failure of the battery can be seen
as a degradation of the separator material, dendritic growth or other
misshappening of the electrodes, and permanent material loss of the active
components.
The physical manifestations of a sudden failure, can be seen as the
destruction of the battery components. Open-circuit failure can be induced
by an applied shock to or excess vibration of the battery. As a result, the
internal components of the battery may become loose or detached, causing
a gap in the electrical circuit.
Short-circuit failure can be caused by an applied shock. It can also be
caused by overheating or overcharging the battery. In a short-circuit
failure, some part of one of the electrodes pierces (caused by shock) or
grows through (caused by overcharging) the separator material in the
electrolyte. This piercing effect will cause the electrical path to be shorted.
If a battery and its replacements seem to be suffering repeated premature
failures, in reoccurring and similar circumstances, the failed batteries
should be sent to a laboratory for dissection and analysis. The problem
may lie in faulty equipment, inappropriate battery usage, or in physical
abuse to the device and its batteries. Resolution of the problem will save
time and money in future battery designs and applications.
6.13. Battery Adapters
A battery adapter is a device that can be used instead of a battery to
provide current to a battery- powered device.
Most battery adapters will convert 60 Hz,
110 V, alternating current (i.e., typical house current) into direct current
(dc) for use by battery- powered devices. Other adapters are designed to be
powered by 12 V automobile batteries, usually by insertion of a plug into
the automobile's cigarette lighter.
An adapter will usually have a dc-output plug that is inserted into the
battery-powered device to provide dc current to the device.
Usually, manufacturers of the more expensive battery-powered devices
(e.g., cellular phones, laptop computers) will provide the customer with a
battery adapter designed especially for that device. The adapter will plug
into a special connector in the device to provide it power. If designed to do
so, the battery adapter will charge the device's batteries as well.
Other manufacturers make generic battery adapters. These adapters will
have a battery-shaped appendage that plugs into a battery-powered device
in place of a real battery and will provide energy equivalent to a real
battery. While this kind of adapter has some advantages (it can be used for
any battery powered device, it can be used when no charged batteries are
available, etc.), those advantages are usually outweighed by the
disadvantages (the power cord is inconvenient and negates the portability
of the device, the battery cover cannot be replaced while the cord is
attached, a multiple-battery device would require multiple adapters, etc.).
7. PRODUCTS AND SUPPLIERS
-------------------------------
Batteries and battery manufacturers and suppliers listed or mentioned in
this section, and elsewhere in this guideline, are listed for the convenience
of the reader. The name of a specific product or company does not imply
that the product or company is, necessarily, the best for any particular
application or device. The lists are, necessarily, not all-inclusive. The list
of Web pages was compiled following a Web search performed in August,
1997. New Web pages may have appeared since then and some which
appear in this list may no longer be available. Other Web pages, that were
not listed in the Web-search database at that time, will also not appear in
this list.
7.1. Battery Manufacturers
The battery manufacturers listed below are some of the manufacturers of
household batteries. They are presented in alphabetical order. All
information was verified in August, 1997.
7.1.1. Battery Engineering
Postal Address:
Battery Engineering, Inc.
100 Energy Drive
Canton, MA 02001
Phone Number:
(617) 575-0800
Web Page:
http://www.batteryeng.com
Email Address:
info.at.batteryeng.com
7.1.2. Duracell
Postal Address:
Duracell, Inc.
Berkshire Corp Park
Bethel, CT 06801
Phone Number:
1 (800) 551-2355
Web Page:
http://www.duracell.com/
7.1.3. Eveready
Postal Address:
Eveready Battery Company, Inc.
Checkerboard Square
St. Louis, MO 63164-0001
Phone Number:
1 (800) 383-7323
Web Page:
http://www.eveready.com/
Email Address:
bunny.at.chas.ts.maritz.com
7.1.4. Rayovac
Postal Address:
Rayovac Corporation
P.O. Box 44960
Madison, WI 53744-4960
Phone Number:
1 (800) 237-7000
Web Page:
http://www.rayovac.com/
Email Address:
customers.at.rayovac.com
-------------------------------
Table 8. Some On-Line Information Available via the World Wide Web
All Web information was verified in August, 1997.
BATTERY MANUFACTURERS
Battery Engineering
http://www.batteryeng.com/
Duracell Batteries
http://www.duracell.com/
Eveready Batteries
http://www.eveready.com/
Kodak Corporation
http://www.kodak.com/
NEXcell
http://www.battery.com.tw/
Panasonic Batteries
http://www.panasonic-batteries.be/home.html
PolyStor Corporation
http://www.polystor.com/
Radio Shack
http://www.radioshack.com/
Rayovac Batteries
http://www.rayovac.com/
Sony Corporation
http://www.sel.sony.com/SEL/rmeg/batteries/
BATTERY DISTRIBUTORS
Battery-Biz, Inc.
http://www.battery-biz.com/battery-biz/
Battery Depot
http://www.battery-depot.com/
Battery Network
http://batnetwest.com/
Batteries Plus
http://www.spromo.com/battplus/
E-Battery
http://e-battery.com/
Powerline
http://www.powerline-battery.com/
-------------------------------
8. A GLOSSARY OF BATTERY TERMS
Ampere-Hour -- One ampere-hour is equal to a current of one ampere
flowing for one hour. A unit-quantity of electricity used as a measure of
the amount of electrical charge that may be obtained from a storage battery
before it requires recharging.
Ampere-Hour Capacity -- The number of ampere-hours which can be
delivered by a storage battery on a single discharge. The ampere-hour
capacity of a battery on discharge is determined by a number of factors, of
which the following are the most important: final limiting voltage;
quantity of electrolyte; discharge rate; density of electrolyte; design of
separators; temperature, age, and life history of the battery; and number,
design, and dimensions of electrodes.
Anode -- In a primary or secondary cell, the metal electrode that gives up
electrons to the load circuit and dissolves into the electrolyte.
Aqueous Batteries -- Batteries with water-based electrolytes.
Available Capacity -- The total battery capacity, usually expressed in
ampere-hours or milliampere-hours, available to perform work. This
depends on factors such as the endpoint voltage, quantity and density of
electrolyte, temperature, discharge rate, age, and the life history of the
battery.
Battery -- A device that transforms chemical energy into electric energy.
The term is usually applied to a group of two or more electric cells
connected together electrically. In common usage, the term "battery" is
also applied to a single cell, such as a household battery.
Battery Types -- There are, in general, two type of batteries: primary
batteries, and secondary storage or accumulator batteries. Primary types,
although sometimes consisting of the same active materials as secondary
types, are constructed so that only one continuous or intermittent discharge
can be obtained. Secondary types are constructed so that they may be
recharged, following a partial or complete discharge, by the flow of direct
current through them in a direction opposite to the current flow on
discharge. By recharging after discharge, a higher state of oxidation is
created at the positive plate or electrode and a lower state at the negative
plate, returning the plates to approximately their original charged
condition.
Battery Capacity -- The electric output of a cell or battery on a service test
delivered before the cell reaches a specified final electrical condition and
may be expressed in ampere-hours, watt- hours, or similar units. The
capacity in watt-hours is equal to the capacity in ampere-hours multiplied
by the battery voltage.
Battery Charger -- A device capable of supplying electrical energy to a
battery.
Battery-Charging Rate -- The current expressed in amperes at which a
storage battery is charge