REFERENCE GUIDE FOR BATTERIES
Terence O’Kelly

Content Links
1. Memorex history
2. History of the battery
a. Luigi Galvanib. Alessandro Volta
A. Voltaic pile
3. Modern battery typesa. Lead-acidb. Alkalinec. Lithium-Ion
d. Lithium Photoe. Metal-Chloride
f. Ni-Cadg. Nickel-Metal Hydrideh. Silver-Zinc
i. Zinc-Air
j. Zinc-Carbon
k. Zinc-Mercury
4. Battery sizes
5. Battery construction
a. Cell arrangements of batteries
i. Parallel cells
ii. Serial cells
6. Battery Terminology
a. Active materialb. Ampere-hoursc. Anoded. Cathodee. Capacity
f. CCVg. Constant current
h. Discharge
i. Drainj. E.V.
k. Internal Resistancel. Ohmm. Powern. Shelf life

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REFERENCE GUIDE FOR BATTERIES
Terence O’Kelly
Memorex has long been one of the world’s foremost suppliers of media for memory storage. Thevery name of the company is a shortened form of “MEMORy EXcellence” that started in 1961 withthe manufacture of half-inch 9-track computer tape and progressed to audio and video cassettes,
digital audio cassettes, and computer diskettes. As storage technology developed, Memorex
expanded to optical storage media such as recordable and rewritable CDs and DVDs and to solidstate storage in the form of flash memory. As memory devices have grown smaller and moresophisticated, Memorex has continued to expand to include another storage medium—power
storage in the form of batteries.
People often associate batteries with an energized bunny and a charged duck, but it
was an unnamed frog who contributed most to the development of the battery bygiving his leg and his life to science. At the end of the eighteenth century Luigi
Galvani, Professor of Anatomy at Bologna University in Italy, described in his recently
published treatise how he had discovered that connecting two lengths of copper wire and iron wire
together so that they touched the frog’s leg on one end and the exposed nerve endings on theother end would make the leg convulse. He attributed the phenomenon to “animal electricity.” Hebelieved that the leg stored electrical energy. Alessandro Volta disagreed. He was convinced thatthe source of power lay in the two different metals used for the wire because a single metal wire
would not produce the same convulsions. His experiments proved that the electrical energy camefrom the two metals separated by various liquids, and he built a “voltaic pile” that could produce a
shock when the ends were touched.

+

Volta’s “Crown of Cups”
Battery of Simple Cells+_

silver disczinc discsalt-water soaked pad

Figure 1

Figure 22

The voltaic pile was a stack of pairs of silver and zinc discs separated by cloth pads soaked inbrine (Figure 1). When someone touched the top silver disc and the bottom zinc disc at the sametime, he felt an electrical shock. There was a problem in the design in that the weight of the metal
discs squeezed the brine out of the pads and down the stack; so in 1800 Volta came up with adifferent solution in the form of a series of small cells holding strips of silver or copper and strips ofzinc dipped into dilute sulfuric acid. A copper wire ran from the top of one metal strip to the next inwhat Volta called “a crown of cups” (Figure 2). If the series or “battery” of simple cells contained ahundred or more cells, a person holding the wires at the end of the first and last cells received atingling sensation indicating that electricity was flowing through the wires. Volta’s battery differsfrom today’s batteries only in the materials and chemicals used and the amount of surface area on
the metal strips. Volta’s design is the grandfather of today’s wildly varying battery types and styles.
Volta experimented with different metals and salt or acid solutions with varying results. His battery
produced electrical energy instead of heat in an electrochemical reaction in a manner explainedlater by chemists who understood the process better. If just the zinc is placed in the acid, it begins
to dissolve and create heat. But when the wire connects the copper and zinc strips, the zinc nolonger gives off the heat. As it begins to dissolve in the diluted sulfuric acid, bubbles of hydrogenform on the copper. As this chemical process takes place, a current of electrons flows through thewire from the zinc to the copper. The electrical power develops in the following way:
1. Pure sulfuric acid is described by the chemical formula H2SO4.
2. Adding water to the pure acid causes the SO4 atoms to separate from the two H (hydrogen)atoms and at the same time take away two electrons, one from each H atom. (This is thereason that some car batteries have to have distilled water added every now and then if
some water has evaporated.)
3. The H atoms now have a positive charge because each lacks a negative electron.
Charged atoms or groups of atoms are called “ions.” The SO4 molecules are now
negatively charged ions.
4. The negative SO4 ions in the solution encourage the dissolution of the zinc into the acid toform zinc sulfate.
5. The acid dissolves the zinc strip, and the dissolved zinc atoms go into the solution as Zn2+
ions. Each dissolved zinc ion is positively charged because it leaves two electrons on thezinc strip.
6. When zinc dissolves in sulfuric acid, the chemical reaction usually produces heat; but inthis case, the excess electron charges on the remaining zinc strip create an electron
current through the wire from the zinc strip to the copper strip.
7. The positively charged H atoms have been busy, too. As they are being abandoned by the
fickle SO4 ions, they deposit themselves on the copper strip.
8. The copper offers each H ion one of its electrons and turns each back to a neutralhydrogen atom, transformed into a bubble of hydrogen on the copper strip.
9. The copper atoms now turn into positively charged copper ions after yielding their electrons
to the hydrogen.
The zinc strips have extra electrons from the Zn2+ ions, and the copper strips are short on electrons
since they have given them to the hydrogen. To balance things again, the electrons flow from thezinc through the wire to the copper and create electrical current.
These chemical reactions are the principle behind all batteries. The materials have changed over
the years to increase efficiency and practicality. The first problem with Volta’s crown of cups wasthat the accumulation of hydrogen bubbles on the copper strip would eventually insulate it fromfurther chemical reaction. Adding a small amount of potassium dichromate solution to the diluted
sulfuric acid allowed it to place oxygen atoms on the hydrogen bubbles, turning them into waterand clearing the copper plate. (This is why a battery that appears to have given up all its energy
can “recover” after an hour or so. The hydrogen insulation dissipates in time.) This chemical fix
decreased the “internal resistance” of Volta’s original design and made this simple cell3

arrangement more efficient. Over the years battery engineers have introduced many newmaterials and designs to overcome one deficiency or another or to enhance a particularcharacteristic. The many different designs account for the differences in battery types, theirelectrical characteristics, and their uses.

BATTERY TYPES
Batteries not only come in all different sizes, they also use very different designs based on theapplications for their use. Some are meant to supply large amounts of current in bursts of energy(high-drain use) while others are used to supply long-lasting supplies of low current power. The
most common types are:Lead-Acid Battery—the Standard Car Battery
The cells of a car battery use large flat plates of lead and lead dioxide instead of strips of copperand zinc. The plates have tips on their upper ends that are the “electrodes” to which the car’s
electrical wires are attached. The lead plate has the negative electrode and the lead dioxide plate
sports the positive electrode. The exchange solution or “electrolyte” is the same dilute sulfuric acidthat Volta used. The chemical reaction is similar to the crown of cups:
1. The lead plate sitting in the acid combines with the acid to form PbSO4 plus one freeelectron. (Pb stands for “plumbum,” Latin for “lead.” It is a heavy, malleable metal used by
the original plumbers to make pipes in the Roman days.)
2. The flow of current from the negative lead plate through the car’s starter to the positive leaddioxide plate creates water on the lead dioxide plate and builds lead sulfate on both plates.
3. As the battery sends more current from the negative pole of the battery through the starterto the positive pole, the acid solution becomes more diluted with water and the lead sulfate
increases, weakening the battery.
4. However, when the car starts running and the generator now charges the battery, thecurrent flowing to the battery’s poles returns the plates to their original lead and leaddioxide states, making the battery reusable.
Each of the cells in a car battery can provide about 2 volts. The typical 12-volt battery has six
cells, each with its own chamber. Looking at the top of a typical battery, one can see the six inlets
for those batteries that require the addition of distilled water to keep the electrolyte solution at theproper acid/water ratio. The very large, flat lead negative plate sits very close to the lead dioxide
plate shaped in a grid pattern in order to provide the largest amount of surface area possible. This
design is to allow the maximum transfer of current needed to turn over an internal combustion
engine, even on the coldest days when the lubricating oil is thick. Batteries such as car batteries
designed to supply short, intense bursts of electrical energy are know as ‘”high-drain” batteries.
Alkaline Battery
These batteries use zinc and manganese-oxide as the electrodes, and an alkaline formulation acts
as the electrolyte. These batteries are excellent for electrical devices that require a steady,uninterrupted flow of current such as wall clocks, flashlights, and portable music players. There
are also high-drain versions of alkaline batteries available, and they do outlast conventional
alkaline types; but since the high-drain design costs twice as much, it is more economical to invest
in two standard alkaline types for the longer power supply. The alkaline battery is increasingly
common since it outlasts the older zinc-carbon “heavy-duty” batteries with little cost penalty and iseasily disposable after it has expired.
There are also rechargeable alkaline batteries on the market that are cheaper than rechargeable
nickel-metal hydride batteries (see below) and do not suffer the power losses in storage that NiMH
batteries do. Unfortunately, they can only be recharged about 25 times, and the amount of charge
life decreases after each recycle.

4Lithium-Ion Battery
These rechargeable batteries are long lasting but not as heavy as other designs. The typicalelectrode is based on cobalt chemistry, but researchers are developing electrodes based on
phosphates or manganese that may offer better characteristics for the future. The favorable
power-to-weight ratio of the lithium-ion battery makes it popular in cell phones and in the more
expensive laptop computers. Lithium-Ion batteries are generally far more expensive than otherbattery types.
Lithium Photo Battery
Battery designs based on lithium, lithium iodide, and lead iodide are high-drain designs capable ofsudden power surges such as those required by the flash devices on cameras. This is thecommon type of battery used in photographic equipment. They are long lasting batteries, lasting
about twice as long as alkaline versions both in use and in storage; but they tend to be rather
expensive, typically about four times more expensive than the alkaline versions.
Metal-Chloride Battery
These are heavy rechargeable batteries capable of supplying current for long periods. These
characteristics have made them the choice for use in battery-powered automobiles.
Nickel-Cadmium Battery (NiCad)
This rechargeable design uses nickel-hydroxide and cadmium as the electrodes in an electrolyte ofpotassium hydroxide. The battery chemistry works best when the battery is drained nearly to its
limit and immediately fully recharged because it has a “memory effect” that leaves it last charged
state as its maximum capacity for the future. Although NiCad batteries are relatively low in energy
density compared to NiMH batteries, their long life and capability of high discharge rates offer
considerable advantages. The cadmium in the battery is a hazardous waste material; so thesebatteries cannot simply be tossed into the garbage when they have expired. They need to beproperly recycled.
Nickel-Metal Hydride Battery (NiMH)
The NiMH battery is renowned for its ability to last through 300 to 600 recharge cycles and keep ondelivering power. That strong point is balanced by the fact that NiMH batteries drain faster thanalkaline batteries, and that drain continues even when the batteries are not being used. Electricaldevices that sit in wait for sporadic use, such as flashlights and remote controls, are the wrong
type for NiMH batteries.
Silver-Zinc Battery
This is another battery with a good power-to-weight ratio in its design.
common in airplanes and other equipment where weight is a critical factor.

That makes it more

Zinc-Air Battery
Like the silver-zinc battery, this design is also lightweight and rechargeable.
Zinc-Carbon Battery
This design is a very common, inexpensive design available in the typical AA, C, and D sizes. The
electrodes are zinc and carbon with an acidic paste pressure squeezed into the casing that acts as
the electrolyte. The paste is what made this design one of the first “dry cell” batteries that did not
rely on a corrosive liquid electrolyte that could leak or spill. The “heavy-duty” moniker is often used
to describe this particular design.
Zinc-Mercury Battery
The zinc-mercury battery is a lightweight, low-drain design common in hearing aids.

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BATTERY SIZES
Batteries can take all sorts of shapes and sizes, as anyone who has ever tried to change a watch
battery has discovered. Since all that is required is the two electrodes (the anode for the negativepole and the cathode for the positive pole and the chemical material creates the energy), thosematerials can take any shape required. The most common types of batteries, however, take a few
specific shapes that are designated by an old combination of letters established years ago by
ANSI, the American National Standards Institute. The IEC, the International ElectrotechnicalCommission, has set new, voluntary designations on batteries; but in the American market people
still refer to the old letter code.

1.5 volts
1.5 volts
1.5 volts
9.0 volts
1.5 volts

D

ANSI Designation 1
D
C
AA
9V
AAA

C

AA

IEC Designation
R20
R14
R6
6F22
R03

9V

AAA

1

The sizes ranged from A to D. The missing “B” size was a battery used in vacuum tube radios up until the
1960’s when both the radios and the B batteries disappeared as transistor radios displaced the older tube
versions. The B battery was taller than the C type and not quite as thick.

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CELL ARRANGMENTS
Batteries differ not only in their composition, size, and shape but also in their voltage and current
flow. Voltage is the amount of electrical force or potential across the two electrodes of the battery.
Current describes the flow of electricity across the electrodes if they are connected to each otherthrough a form of resistance, which could be a filament in a light bulb, an electrical motor, or someother electrical device. (If the two electrodes are directly connected with a wire and no resistanceat all, the circuit is known as a “short circuit” with all that implies—sparks, heat, and potential fire aswell as damage to the battery.) Current describes the flow of electricity; voltage describes thepower pushing it. If electricity were water, a rain shower would be high current (fast moving) but
with low voltage (not a lot of force in each drop). A pinhole leak in Boulder Dam, on the other
hand, would be similar to low current, high voltage—not much flow, but a lot of force behind it. A
shock of 50,000 volts is about the same as a static spark resulting from walking on a rug in a dry
room in winter—lots of voltage, very little current. A bolt of lightning has about the same voltage as
the static spark—but it is the tremendous current of the lightning bolt that lights up the sky anddoes the damage.
Batteries are most often just what the word originally meant: a series or battery of cells connected
together to produce electricity. The way the cells are arranged determines the voltage of thebattery and its ability to deliver current. There are two basic arrangements: parallel and serial.
Parallel Cells
Just as in a parallel circuit, a parallel design of cells allows the voltage to remain the same whilecurrent flow increases depending on the number of cells. In Figure 3 below, the number of 1.5-voltcells is four, each capable of supplying a particular amount of current. In the parallel arrangement,
the voltage of the total cells connected together remains 1.5 volts; but the cells together can deliver
four times the current flow of just one of the four cells. A device requiring low voltage in a large
burst of energy would use a battery with the parallel cell design.

+

+

+

+

-

-

-

-

1.5 V

1.5 V

1.5 V

1.5 V

1.5 V

Parallel Arrangement
Total Voltage = Voltage of 1 cell X 1
Total Current = Current of 1 cell X number of cells

Figure 37Serial Cells
Cells arranged in a serial design will increase their voltage potential by the number of cells
connected in the series. The current capability remains the same as that of each single cell in theseries. In the example in Figure 4 below, the total potential of the four 1.5-volt cells is 6 volts. The
current is no different from that of a single cell in the series.

+

+

+

+

-

-

-

-

1.5 V

1.5 V

1.5 V

1.5 V

6.0 V

Serial Arrangement
Total Voltage = Voltage of 1 cell X number of cells
Total Current = Current of 1 cell X 1
Figure 4

The individual cells of a battery often produce little voltage. The arrangement of the cells within thebattery determines its total voltage. The typical 12-volt car battery has 6 cells in it, each capable of
2 volts. The serial arrangement brings the total voltage to 12 volts, and the large plates insideincrease the amperage to what is required. A nine-volt battery typically has six 1.5-volt cells
arranged in series inside its case.
Devices that require a particular current flow or voltage generally rely on existing battery types todeliver the power the correct way. The batteries themselves can be arranged in parallel or inseries, depending on the requirements. This makes it much easier for the consumer to get thedevices working without having to get involved in calculations of electrical circuitry. The only
important requirement is to put the batteries in the device properly so that the positive electrodes
and negative electrodes are facing the correct directions.

BATTERY TERMINOLOGY
Battery data sheets and sales literature use a lot of electrical terms to describe the performanceand operation of the batteries. Many of the terms are only vaguely familiar to users, and it helps tounderstand what the terms mean in order to understand the claims made for battery performance.
Active Material: the material at the positive or negative electrode that reacts chemically to move theelectrons to store an electrical charge. The battery type usually takes its name from the type ofactive material used in the battery.

8

Ampere: a measure of the flow of current through a circuit.
Ampere-hours: a measure of the electrical charge passing through a circuit at a rate of one ampere
per hour. The measure is taken by multiplying the amount of current in amperes time the numberof hours. Of course a small battery is incapable of sustaining that amount current flow, so thefigure is generally measured in thousands of an ampere or milli-amperes.
Anode: the negative electrode that loses the electrons in a chemical reaction.
Cathode: the positive electrode that accumulates the electrons from the anode.
Capacitance: a ratio of an increased charge on a conductor to the corresponding change involtage.
Capacity: the amount of electrical output a battery can sustain over a period of time, generally
expressed in mAh, or milliamps per hour. The measurement is taken on a specific load at a
specific temperature until the voltage drops to a specified point. The load represents a resistancetypical of the application in which the battery is used.
CCV: Closed Circuit Voltage. The voltage of a battery measured under a specific load or
resistance and time interval. An open circuit is one in which there is no connection between theelectrode or anode and no current flow. A short circuit is one in which there is a direct connection
between the anode and cathode and no resistance at all! Short circuits are what lead touncontrolled chemical reactions and the danger of fire.
Constant Resistance: resistance that does not vary over the life of the battery as the battery’s
voltage and current decline.
Discharge: the withdrawal of electrical energy from a battery, usually during its operation.
Drain: the withdrawal of current from a battery whether or not it is connected to a circuit.
e.v.: ending voltage. This is the lowest level of voltage in the battery at which either the battery canstill operate any devices connected to it or below which it should not operate.
Impedance: opposition to the flow of alternating current that is a combination of resistance,
inductance, and capacitance.
Inductance: the property of a circuit by which the flow of current through a conductor produces anelectro-magnetic field and the corresponding electro-motive force.
Internal Resistance: (Ri)—the opposition of direct current flow within the battery itself that results ina drop in closed circuit voltage.
Ω: Ohm--the standard unit of electrical resistance that is equal to a conductor in which a current of
one ampere is produced by a potential of one volt across the conductor’s terminals.
Power: the amount of work an energy source can perform, expressed in watts. Watts are theproduct of the voltage times the current.
Shelf Life: The amount of time a cell or battery will retain a specified percent of its rated capacity,
typically under ambient storage conditions.

9Voltage: the measurement of electro-motive force or electric potential. One volt is defined as theamount of potential between two points of a conductor with a constant current flow of 1 ampere
producing 1 watt of power.
Watt: a unit of electrical power.

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