TECHNICAL PAPER #25
James H. Hahn
Lester H. Smith, Jr.
1600 Wilson Boulevard, Suite 500
Arlington, Virginia 22209 USA
Tel: 703/276-1800 . Fax: 703/243-1865
[C]1985, Volunteers in Technical Assistance
This paper is one of a series published by Volunteers in
Assistance to provide an introduction to specific
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their
They are not intended to provide construction or
details. People are
urged to contact VITA or a similar organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
The papers in the series were written, reviewed, and
almost entirely by VITA Volunteer technical experts on a
Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time.
VITA staff included Maria Giannuzzi
as editor, Suzanne Brooks handling typesetting and layout,
Margaret Crouch as project manager.
The author of this paper, VITA Volunteer Horace McCracken,
president of the McCracken Solar Company in Alturas,
The co-author, VITA Volunteer Joel Gordes, is currently the
design analyst for the State of Connecticut's Solar Mortgage
Subsidy Program. The
reviewers are also VITA volunteers.
Dunham has done consulting in solar and alternative sources
energy for VITA and AID.
He has lived and worked in India, Pakistan,
and Morocco. Mr.
Dunham has also prepared a state-of-the-art
survey on solar stills for AID.
Jacques Le Normand is Assistant
Director at the Brace Research Institute, Quebec, Canada,
which does research in renewable energy.
He has supervised work
with solar collectors and has written several publiations on
solar and wind energy, and conservation.
Darrell G. Phippen is a
mechanical engineer and development specialist who works
Food for the Hungry in Scottsdale, Arizona.
VITA is a private, nonprofit organization that supports
working on technical problems in developing countries.
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to
maintains an international Inquiry Service, a
specialized documentation center, and a computerized roster
volunteer technical consultants; manages long-term field
and publishes a variety of technical manuals and papers.
By VITA Volunteer Lee Merriman
Batteries have been in use for many years, but today there
greater demand for battery power than ever before.
interest has been brought about not only by new developments
also by the diversity of uses for batteries in civilian,
and military applications.
This paper provides a basic understanding of batteries and
their development from the early 1800s to the present
and development continues in an effort to solve the inherent
weakness of batteries, namely, how to pack more energy
into a smaller package.
An electric cell or battery is a device that transforms the
chemical energy contained within its active materials
into electrical energy by means of an electrochemical
This type of reaction involves the transfer of electrons
material to another through a conducting solution.
batteries played an important role in the early days of
development both in the United States and in Europe.
In 1800 an Italian scientist named Volta discovered that by
immersing two dissimilar conductors in a chemical solution
electromotive force (EMF) or voltage was established between
Figure 1 illustrates a simple Voltaic cell.
The solid conductors of the cell are called electrodes and
conducting liquid the electrolyte.
A cell consists of two electrodes
and an electrolyte.
A battery consists of one or more
cells. The voltage
of the cell depends upon the material of the
electrodes and the electrolyte.
The electric current output and
the power of the cell are dependent upon the plate
the weight of the electrode material.
There are two general types of batteries in use today: the
type or "dry cell" and the secondary storage
primary battery produces a current by discharge action when
of the electrodes of the cell is decomposed during use.
of cell cannot be restored to use again by recharging and
entire cell must be discarded when it is no longer
cells, on the other hand, are chemically reversible and can
be charged and discharged over many cycles of operation
In the simple voltage cell shown in Figure 2, when two
metals, zinc and copper, are suspended in an electrolyte of
dilute sulfuric acid, a potential of approxiamtely 1.10 volts
will exist between the electrodes.
The zinc electrode will be
negative and the copper electrode will be positive.
switch in the external load circuit is closed, a current
flow through the load (energy-absorbing device) and battery
accordance to Ohm's Law.(*) As the load current continues to
hydrogen as bubbles will appear and cover the copper plate,
the zinc plate will gradually dissolve.
The main disadvantage
with this cell is that the gas bubbles increase the internal
resistance of the cell, causing current output to decrease.
(*) The direct current flowing in an electrical circuit is
proportional to the voltage applied to the circuit.
of proportionality R, called the electrical resistance, is
by the equation V = RI, in which "V" is the
applied voltage and
"I" is the current.
II. TECHNOLOGY VARIATIONS
Several different types of primary-type wet cells were
and used in the United States.
Most notable among these were the
gravity cell, the caustic-copper oxide cell, the
cell, and the Lelanche cell.
Each cell had its own operating
characteristics, and current capacities ranged from less
ampere (amp) for the Lelanche cell to several hundred
the caustic-copper oxide cell.
The British Post Office developed
a wet cell known as the Daniel's cell, which offered several
outstanding operating features.
There were two main difficulties with the primary-type cell
construction, deterioration by local action and cell
Local action is an internal chemical action inherent to
batteries; the life of the cell is gradually diminished even
though no load is connected to its terminals.
Local action is
defined as the discharge of active material of either plate
to some impurity in the electrolyte or plate material.
action causes the formation of short-circuited cells, which
the metal to deteriorate.
Cell polarization is caused by hydrogen bubbles being
on the cathode when current flows through the cell.
the terminal voltage and increases the internal resistance
methods for neutralizing this polarizing effect
were used, either by chemical or mechanical construction,
led to the development of the air-depolarized cell.
In the air-depolarized cell, the electrode was made of a
absorbent form of carbon and was suspended above the
level. Since the
carbon electrode was not immersed in the electrolyte
solution, polarization of the cell was prevented.
operation, oxygen surrounding the porous surface of the
electrode combines with the hydrogen evolved at the surface
the carbon electrode and electrolyte.
Good ventilation was required
to maintain a satisfactory air supply for operation.
Edison carbon cell and the Carbonaire battery were
of the air-depolarized type.
Wet primary-type cells have largely
been replaced by the secondary-type storage battery.
The modern day "dry cell," which was developed by
Lelanche in 1868, is a modification of the old Lelanche wet
The difference is that only sufficient water is added to the
electrolyte to moisten an absorbent lining.
The modern dry cell
is the most widely used of all primary batteries today
because of their low cost, reliable performance, and
cell batteries are made in ratings of 1.5, 3,
6, 7.5, 9, 22.5, 45, 67, and 90 volts.
The most common type of construction for a dry cell is shown
The cell in Figure 3 uses a carbon rod for the anode or
terminal and an outside zinc container (case) for the
terminal. The zinc
case has an inner lining of absorbent paper
material which is saturated with the electrolyte.
between the electrodes is filled with a mixture of crushed
manganese dioxide, and graphite.
Manganese is added as a depolarizer.
The electrolyte is salammonic and zinc chloride.
top of the case is sealed with a sealing compound and the
container is enclosed in a paper container.
The voltage of a new
dry cell is 1.4 to 1.6 volts.
Dry cell batteries fall into three general classes: (1)
batteries usually 1-1/4 inch in diameter and 2-1/2 inches
high with a current capacity of about 3 amp-hours; (2) large
cells, more commonly referred to as the Number 6 dry cell,
2-1/2 inches in diameter and 6 inches high with a
current rating of about 30 amp-hours; and (3) the "heavy
and high voltage types, which might be one cell or a
of cells, used in industrial service with current capacities
50 amp-hours or greater.
The ampere-hour capacity is the rate of
discharge a battery can maintain for a given period of time,
usually eight hours.
For example, a 30 amp-hour rated battery
normally could supply about 3-1/2 amps for eight hours.
used, however, dry cells provide less than their rating.
The shelf life is limited by local action and for that reason
some manufacturers stamp a service date on the outer
each cell. Local
action causes eventual deterioration of the
battery, and after about one or two years storage, the
Since the zinc electrode forms part of the outer
wall, its gradual destruction weakens the cell structure,
the developed hydrogen gas builds up internal pressure, it
rupture and spill its corrosive contents.
For this reason, equipment
should never be stored with dry cells over long periods of
time. Dry cells
require no maintenance and when they no longer
operate are discarded and replaced.
A more recent type of dry cell developed is the Ruben or
cell (Figure 4).
This cell was developed during World War II by
Ruben Laboratories and P.R. Mallory Company for operating
electronic equipment requiring high current power.
This cell is
made in two forms: the "roll anode" and the
"button type." The
anode is amalgamated zinc and the cathode is a mercuric
depolarized material mixed with graphite.
The electrolyte is a
solution of potassium hydroxide (KOH) containing potassium
These cells are far superior to the Lelanche dry cell owing
to their compact size, flat voltage characteristic, and very
shelf life. The
no-load voltage of these cells is 1.34 volts.
Several advanced developments have been made in small
both primary and secondary-type cells, which include the
magnesium, alkaline, silver-zinc, and lithium.
Table 1 lists the
characteristics and applications of these cells.
SECONDARY STORAGE BATTERIES
Since 1965, there has been renewed interest in using storage
batteries in power systems.
This is because modern power consumption
involves very uneven load demands and increasing peak load
demands. When a
system must deliver more power (increase in load
demand), the supplier can meet the demand by either
additional generator onto the system or switching a charged
battery bank onto the line.
The latter requires a much smaller
The revival of batteries as power system units primarily has
begun with small independent systems such as wind- or
generators. In such
systems, storage batteries perform
two important functions.
First, during periods of low load demand,
the system battery can store much of the generated energy,
which would otherwise be lost to the system.
stored during the off-peak period is available during times
peak load demand.
The importance of the latter can be illustrated
with the following quantitative example: Suppose the
capacity of the battery has a discharge power rate equal to
of the generator power capacity ([P.sub.B] = 0.5
[P.sub.G]). This means that
under normal conditions, during periods of high load demand,
generator-battery combination can for several hours serve a
of up to 1.5 times what the generator alone could serve.
Another reason for the increased interest in secondary
batteries is the need for backup power for some of the newer
example, most modern computers involve some form
of "volatile" storage of information, that is, the
lost if power is removed.
To guard against this possibility, many
computer systems use "uninterruptible" power
systems, based on
storage batteries, to supply electrical current to the
equipment when commercial power is lost.
The storage battery, constructed with secondary wet cells,
similar in action to a primary cell, except the chemical
involved are practically completely reversible.
Once the cell is
discharged, current from an external source, passed through
cell in the opposite direction, will substantially restore
battery to its original charged condition.
There are three types of storage batteries currently
(1) the lead-acid type; (2) the nickel-iron or alkaline
(Edison cell); and (3) the nickel-cadmium or alkali-type
The lead-acid battery is the most widely used type of
today because of its low cost, reliability, good performance
characteristics, and wide application.
This battery is manufactured
in many sizes and capacities ranging from 1 amp-hour up to
several thousand amp-hours rating.(*)
The storage cell uses reactive sponge lead for the negative
electrode (Pb), lead dioxide for the positive electrode (Pb0
and dilute sulfuric acid for the electrolyte.
materials have little structural strength and must be
on plates or grids.
The grid of the battery plate has two functions:
first, it supports the active plate material; and second,
it serves as a conductor to connect the plate terminal to
parts of the active material.
Lead storage battery plates are divided into two types, the
Plante (formed) and the Faure (pasted), as shown in Figure
the Plante-type of construction the active material is
formed of pure lead by an electrochemical process from the
metallic lead of the supporting grid.
In the Faure-type the
active material is applied to the supporting grid in the
a paste follwed by a setting, drying, and forming operation.
Figure 5 shows the Plante (A) and Faure (B) lead cell
cell assemblies are soldered together to form positive and
groups which are interleaved together to make up the
Separators are placed between the electrodes,
and the complete element is placed in a container and
use of large plates with close spacing limits the internal
of the battery to a low level.
Figure 6 shows a cutaway
view of the lead storage cell.
During discharge the battery material of both plates is
into lead sulfate.
The amount of lead sulfate formed onthe plates
and the amount of acid lost from the electrolyte are in
proportion to the rate of discharge.
The reverse action takes
place when the cell is charged.
Cell chemical reactions are
represented by the following equation; however, this is a
simplified form as the actual action is much more complicated.
(*) Battery ampere-hour rating is normally based upon an
At the positive plate:
HS[O.sub.4][sup.-] + [3H.sup.+] + [2e.sup.-](*) -----> PB[SO.sub.4] +
At the negative plate:
Pb + HS[O.sub.4][sup.-] -----> Pb[SO.sub.4] + [H.sup.+] +
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The combined cell reaction for both discharge and charge is
by the following equation:
Pb[O.sub.2] + Pb + 2[H.sub.2] S[O.sub.4] <======
2Pb[SO.sub.4] + 2[H.sub.2]O + electrical energy
On discharge the acid separates from the electrolyte and
chemical combination with the plates, changing it to lead
As discharge continues, additional acid is drawn from the
electrolyte until current will cease to flow.
The water, formed
by the loss of acid to the plates, lowers the remaining
gravity(**) of the electrolyte.
In common practice, discharge is
always stopped before the plates have entirely sulfated,
once entirely sulfated, battery condition cannot be
back to active material on charge.
On charge the reverse action
takes place: the acid in the sulfated plates is driven back
the electrolyte, and the S[O.sub.4] combines with hydrogen
in the water
to form additional sulfuric acid ([H.sub.2][SO.sub.4]).
Electrolyte for lead-acid cells is dilute sulfuric
acid. For a
fully charged battery the specific gravity varies from 1.200
1.30 and when discharged 1.150 (pure water measures
specific gravity is measured by a syringe-type hydrometer as
shown in Figure 7, and values are temperature corrected.
(*) The symbol e- stands for electrons.
(**) Specific gravity is defined as the ratio of weight of a
volume of a substance to an equal volume of pure water.
The voltage of a lead cell is approximately 2.10 volts at no
but is higher when being charged.
Normal voltage on charge is
2.15 volts and as the cell approaches full charge this value
rapidly increases to between 2.5 and 2.6 volts.
This later interval
of charge is known as the "gassing period."
Gassing of the
electrolyte at any time during charging should be avoided as
charge rate is too high.
As a cell reaches its final fully
charged condition, a high current is not advisable as this
current decomposes the water in the electrolyte, which is
off in the form of gas.
The lead-acid battery has several disadvantages:
(1) cells are
temperature sensitive and lose power in cold temperatures;
cell plates tend to buckle and distort on sustained, high
service, and (3) special care must be observed when a
not used for long periods, otherwise the cells will sulfate.
The nickel-iron or alkaline battery was developed to
inherent disadvantages of the lead-plate cell.
It is a radical
departure from it in both construction and operation.
United States this battery is known as the "Edison
after its inventor Thomas A. Edison.
Figure 8 shows the construction
of a typical cell. The
positive plate consists of steel
tubes containing nickel hydrate and nickel added in
layers. The negative
plate is formed of flat steel boxes or
pockets which are perforated and packed with iron oxide
Sheet-steel grids support these tubes and pockets, which are
bolted together to form positive and negative cell
terminals and the steel container are nickel plated.
and insulating parts are made of rubber.
The cell uses an
electrolyte of 21 percent solution of caustic potash
small amount of lithium hydrate.
The chemistry of this cell is quite complicated, and the
reaction occurring inside the cell is entirely different
that of the lead cell.
The electrolyte acts merely as a conducting
medium and does not enter into combination with any of the
active plate material during operation.
Its specific gravity
remains practically constant over the complete cycle of
Condition of battery charge or discharge is determined
by a voltmeter reading and not by the specific gravity of
the electrolyte. The
alkaline battery cell reaction is:
[Fe.sub.2] + 2NiOOH + KOH + 2[H.sub.2]O ------->
[Fe.sub.2][(OH).sub.2] + 2Ni[(OH).sub.2] + KOH + electrical
The voltage of each cell is approximately 1.50 volts on open
circuit, but is higher on charge and lower under load
These batteries are given an ampere-hour capacity rating
upon their rate of discharge up to the final voltage of 1.00
cell. Some current
ratings are based upon a 5-1/2-hour continuous
discharge rate, while others are based upon a 3-1/2-hour
Unlike the lead-cell battery, there is no minimum voltage
which this type of cell cannot be discharged.
In fact, this cell
can be discharged to zero volts, short-circuited at its
and left in this condition for an indefinite period.
is the method by which an alkaline battery is put into
Also, this cell can be accidentally overcharged, charged in
wrong direction, and momentarily short-circuited without
Alkaline batteries are not injured by freezing and an
with a specific gravity of 1.200 at 15.5[degrees]C
(60[degrees]F) freezes solid
at -66[degrees]C (-87[degrees]F).
The electrolyte of this cell gradually deteriorates
during use and must eventually be changed.
The main advantages of the nickel-iron cell are: (1) it is
extremely light and strong owing to its steel construction;
it offers an indefinitely long life; and (3) it overcomes
cell sulfating problem of the lead-acid battery.
disadvantage is its high first cost and high internal
Nickel-cadmium or Nicad batteries, a relatively new addition
storage cells, were developed in Europe.
These batteries consist
of interleaved assemblies of positive and negative plates
in a sealed steel container.
The positive active material, nickel
hydroxide, and the negative active material, cadmium oxide,
encased in identical, finely perforated steel pockets.
are made up of rows of these pockets, which are crimped and
formed into steel frames.
Positive and negative plate assemblies
are bolted together to heavy steel bus bars.
Plate groups are
interleaved and separated by thin plastic rods.
The cell electrical
terminals and case are nickel plated.
The electrolyte is a
solution of specially purified caustic potash (potassium
dissolved in distilled water.
Figure 9 shows a cutaway view
of the Nicad battery.
The simplified cell reaction is:
Cd + 2NIOOH + KOH + 2[H.sub.2]O ------> Cd[(OH).sub.2] +
2Ni[(OH).sub.2] + KOH + electrical
During charge or discharge of the cell, there is practically
change in the specific gravity of the electrolyte.
Edison cell, the sole function of the electrolyte is to act
conductor for the transfer of hydrogen ions from one
the other. The
voltage rating of each cell is 1.20 volts on open
circuit; when connected to an external load, this voltage
fairly constant up to approximately 90 percent of its rated
amp-hour rating of the Nicad cells is based upon a
final discharge voltage of 1.10 volts per cell.
cells, Nicad batteries will be damaged by repeated
below their minimum cell rating of 1.10 volts.
have a temperature operating range from -51[degrees]C
(-60[degrees]F) to 93[degrees]C
Nicad batteries are vibration and shock resistant due to
steel construction; hold their charge well during long idle
periods; maintain a constant voltage source during
are not damaged by overcharge.
These batteries can be mounted in
any position on discharge.
Like the Edison cell, the Nicad battery
has a high first cost as compared with the lead-acid
however, this high cost is offset by their longer life
span. A comparison
of lead-acid, alkaline, and Nicad batteries is
presented in Table 2.
2. Comparison of Lead-Acid, Nickel-Iron,
and Nickel-Cadmium Batteries
2.0 20 to 30
2.2 to 46
1.25 (-51) to 93
General Maintenance Procedures for Storage Batteries
Proper maintenance is essential for continued trouble-free
of storage batteries.
While the cell construction is different
for the several types, maintenance is similar for all types
and consists of the following general procedures:
Keep cells clean and dry;
Check electrolyte level regularly;
Keep batteries charged at all times; and
Keep impurities of all kinds out of cells as
harmful effect and eventually ruin them.
tools or utensils (hydrometers, funnels, etc.)
been used to service other electrolytes different
required for that specific battery,
tools used for lead-acid batteries.
Refer to manufacturers' recommendations and
The electrolyte of the lead-acid cell never requires
except for loss due to accidental spills.
However, in the Edison
and Nicad cells there is a gradual deterioration of their
which must eventually be replaced over the life of the
BIBLIOGRAPHY/SUGGESTED READING LIST
Baumeister, T., ed. Mark's Standard Handbook for Mechanical
7th Edition. New
York, New York: McGraw-Hill Book
Carr, C.C. Craft's American Electrician's Handbook. 8th Edition.
New York, New
York: McGraw-Hill Book Company, 1961.
Fink and Batey.
Standard Handbook for Electrical Engineers. 11th
York, New York: McGraw-Hill Book Company, 1978.
Hubert, Charles I.
Preventative Maintenance of Electrical Equipment.
New York, New
York: McGraw-Hill Book Company, 1969.
Knowlton, A.E., Standard Handbook for Electrical Engineers.
York, New York: McGraw-Hill Book Company, 1949.
McGraw-Hill Encyclopedia of Science and Technology. 5th
New York, New
York: McGraw-Hill Book Company, 1982.
Timbre and Bush.
Principles of Electrical Engineering. 3rd Edition.
New York, New
York: Wiley and Sons, Inc., 1946.
Wolf, Stanley. Guide
to Electronic Measurement and Laboratory
Englewood Cliffs, New Jersey: Prentice Hall,
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