Download Cells & Batteries

NE 139
6029G
Assessments
Why Study Cells & Batteries
Increasing reliance on batteries

Alternative power supplies
Solar cells
Wind Turbine
Diesel Generator
Batteries
Inverter
Low
Voltage
Why Study Cells & Batteries
Increasing reliance on batteries
Alternative power supplies
 Cordless Drills
 Hybrid cars
 Supply back-up

Can the batteries be fully discharged?
 Can the battery be left flat?
 Can you use a car battery for a solar power system?

Chemical Effect of Current
Electrical current causing chemical change

Electro-plating (electro-deposition)

Splitting water into Hydrogen & Oxygen

Lightning thought to have made the basic building blocks of
life on earth.

Used to stop corrosion (Cathodic protection)

Refining of metals (Copper)

CHARGING OF BATTERIES
BACKGROUND
Periodic Table
Page 437
Every element has a symbol
Lead=
Sulphur =
Oxygen =
Hydrogen =
Pb
When “Compounds” are made the
S
O elements symbols are grouped together
H
Water= H2O
Hydrogen x2
Oxygen
BACKGROUND
When compounds are made the electrons
may be liberated creating:
Positive Ions Compounds lacking electrons
Free Electrons
Negative Ions Compounds with excessive electrons
BACKGROUND
Processes that produce electric charge from a
chemical reaction are:
Batteries
Fuel Cells
Cells connected together
Developed to a usable form by NASA for
Mercury, Apollo, and Skylab missions
Fuel cell acts as a “combustion” chamber. Converting high energy
fuel ( Hydrogen) with Oxygen to electric current.
FUEL CELLS
OXYGEN
ELECTRIC CURRENT
WATER
HYDROGEN
HEAT
Efficiency  45%
Can be any fuel(gas) provided the electrode and
membrane are correctly chosen
ELECTRIC CELLS
An electric cell contains three parts, namely:
Acid
Alkali (Base)
Electrolyte
Salt
Cathode
Anode
Discharging
Known as a Voltaic Cell
Negative electrode or Plate
Positive electrode or Plate
ELECTRIC CELLS
An electric cell contains three parts, namely:
Acid
Alkali (Base)
Electrolyte
Salt
Anode
Charging
Cathode
Known as a Electrolytic Cell
Negative electrode or Plate
Positive electrode or Plate
ELECTRIC CELLS
Anode
Cathode
+
Electrolyte
-
-
+
+
ELECTRIC CELLS
Chemical reaction between two electrodes and the
electrolyte they are in contact with
Primary Cell
 Chemical reaction is irreversible
 One electrode is “eaten” away
 When cell is constructed, all cell’s energy is present
Secondary Cell
 Chemical reaction is reversible
 Chemical change does not destroy electrode
 Once made, has to be charged
LUIGI GALVANI
1737 - 1798
PRIMARY CELLS
1780
Luigi Galvani discovered that when two different metals
were connected together and then both touched to
different parts of a nerve of a frog leg at the same
time, they made the leg contract. He called this "animal
electricity".
ALESSANDRO GIUSEPPE ANTONIO ANASTASIO VOLTA
1745 - 1827
PRIMARY CELLS
1800
Voltaic Pile (Copper, Zinc, Sulphuric acid
PRIMARY CELLS
Cell Voltage:
Dependant on electrode type
See Table 3.1 Page62
What voltage will the cell’s voltage
be if Copper & Zinc is used?
Zinc = -0.76 V
Copper = +0.34 V
Voltage difference =
+0.34 - (-0.76) = 1.1 V
Copper electrode = Positive terminal
PRIMARY CELLS
Cell Voltage:
Dependant on electrode type
See Table 3.1 Page62
What voltage will the cell’s voltage
be if Gold & Aluminium is used?
Aluminium = -1.76 V
Gold = +1.42 V
Voltage difference =
+1.42 - (-1.76) = 3.18 V
Gold electrode = Positive terminal
PRIMARY CELLS
Cell Voltage:
Dependant on electrode type
See Table 3.1 Page62
Cell Current:
Dependant surface area of electrode (Plate)
Copper
+
+
H
ZINC COPPER CELL
Hydrochloric Acid
H+
HCl
Zn++
Cl-
H+ HCl ClZnCl
Zinc
-
ZINC COPPER CELL
Problems with this type of cell
Hydrogen gas bubbles stick to the copper electrode
Reduces surface area of electrode
Effect known as “Polarisation”
Chemicals (Depolarisers) are added to reduce this effect
ZINC COPPER CELL
Problems with this type of cell
Any impurities in Zinc electrode will act as a small cell
and eat the electrode away even if the cell is not
connected
Effect known as “Local Action”
Causes the cell to go flat or have a “shelf life”
JOHN FREDERIC DANIEL
1790 - 1845
THE DANIELL CELL
1836
First attempt to remove the
problem of Polarisation
Used second electrolyte to
consume the hydrogen
GEORGES LECLANCHE
1839 - 1882
THE LECLANCHE CELL
1866
Positive electrode = Carbon
Negative electrode = Zinc
Electrolyte = Ammonium Chloride
Depolariser = Manganese Dioxide
Zn(s) + 2 MnO2(s) + 2 NH4Cl(aq) → ZnCl2 + Mn2O3(s) + 2 NH3(aq) + H2O
THE ZINC CARBON CELL
1866
THE ZINC CARBON CELL
1866
Positive electrode = Carbon
Negative electrode = Zinc
Electrolyte = Ammonium Chloride
Depolariser = Manganese Oxide
Zn(s) + 2MnO2(s) + 2NH4+(aq) → Mn2O3(s) + Zn(NH3)22+(aq) + H2O(l)
THE ZINC CHLORIDE CELL
Electrolyte = Zinc Chloride
Zn(s) + 2 MnO2(s) + ZnCl2(aq) + 2 H2O(l) → 2 MnO(OH)(s) + 2 Zn(OH)Cl(aq)
THE ALKALINE CELL
Alkaline Cells Alkaline watch batteries are primarily used where cost is a factor.
Construction is similar to Lithium cells. Voltage rated at 1.5 volts. Next time you find a
free watch in your pack of breakfast cereal, chances are it will be powered by a Zinc
Alkaline cell.
Advantages
Cheap to make. Environmentally safe. Good for low and intermittent high drain
applications. Will keep that el-cheapo quartz watch going for months!
Disadvantages
Only about half the capacity of a silver oxide cell. Voltage not very constant during its
life. Relatively short shelf life, similar to carbon zinc cells in its characteristics, but with
about double the stored energy capacity.
Uses
Suitable for applications where a cheap alternative is required. Wouldn't risk putting one
in my Accutron even if I could find one to fit.
A) Cell top (-ve electrode)
B) Anode of Zinc + Electrolyte gel
C) Nylon seal
D) Electrolyte in Separator, Anode and Cathode Material.
E) Cathode of Manganese Dioxide
F) Absorbent separators containing electrolyte
G) Cell Can (+ve electrode)
Cylindrical alkaline batteries are produced with a high surface area zinc anode, a high
density
manganese dioxide cathode, and a potassium hydroxide electrolyte. A cutaway (fig. 4)
of a typical
cylindrical alkaline battery is illustrated in the following diagram:
Cathode is a mixture of high purity electrolytic manganese dioxide and carbon
conductor.
Anode is a gelled mixture of zinc powder and electrolyte.
Separators of specially selected materials prevent migration of any solid particles in the
battery.
Steel can confines active materials and serves as the cathode collector.
Brass collector serves as the anode collector.
Positive and negative covers provide contact surfaces of nickel-plated steel.
Non-conductive plastic film label electrically insulates the battery.
Nylon seal provides a safety venting mechanism
THE MERCURY CELL
Mercury batteries have been the mainstay of watch batteries for almost 50 years. These
cells are rated at 1.36 volts. Due to increasing concerns over waste mercury finding its
way into our food, the manufacturing of these batteries has virtually stopped.
Advantages
Extremely constant voltage over its useful life. Suitable for low drain and intermittent
high drain applications. Long shelf life - up to 3 years.
Disadvantages
Contains mercury, which in certain forms is highly toxic to humans and animals.
Uses
Excellent for Accutrons, as they were designed originally to operate with these cells.
Were used in nearly all applications requiring small constant voltage cells, ie, watches,
hearing aids, portable scientific instruments etc.
A) Cell top (-ve electrode)
B) Anode of powdered zinc + electrolyte gel
C) Nylon seal
D) Electrolyte
E) Cathode of Mercuric Oxide and Graphite
F) Absorbent separator of fabric and electrolyte
G) Barrier separator membrane.
H) Cell Can (+ve electrode)
I) Metal sleeve to support the nylon case seal
THE SILVER OXIDE CELL
A silver oxide battery (IEC code: S), also known as a silver–zinc battery, is a primary cell
(although it may be used as a secondary cell with an open circuit potential of 1.86 volts).
Silver oxide batteries have a long life and very high energy/weight ratio, but a
prohibitive cost for most applications due to the high price of silver. They are available
in either very small sizes as button cells where the amount of silver used is small and
not a significant contributor to the overall product costs, or in large custom design
batteries where the superior performance characteristics of the silver oxide chemistry
outweigh cost considerations. The large cells found some applications with the military,
for example in Mark 37 torpedoes or on Alfa class submarines
The silver oxide/zinc alkaline primary battery is the predominate system of the
miniature battery product
line. It typically can be used in watches, calculators, photoelectric exposure devices,
hearing aids, and
electronic instruments. Its general characteristics include:
Higher voltage than comparable mercury batteries
Flatter discharge curve than alkaline manganese dioxide batteries
Good low temperature characteristics
Good resistance to shock, vibration, and acceleration
Low and essentially constant internal resistance
Excellent service maintenance; in excess of 90% after storage at 21°C(70°F) for five
years
Available in voltages ranging from 1.5 to 6.0 volts and a variety of sizes.
Silver oxide batteries contain a cathode of silver oxide with a low percentage of
manganese dioxide and
graphite, an anode of high surface area zinc, and a highly alkaline electrolyte consisting
of either sodium
hydroxide or potassium hydroxide. The open circuit voltage of silver oxide batteries is
1.6 volts. The
operating voltage at typical current drains is 1.55 volts or more. Silver oxide batteries
offer a higher flat
operating voltage characteristic than mercuric oxide batteries as illustrated in the
following diagram:
Cathodes are a mixture of Ag2O and conductor.
Anodes are a gelled mixture of amalgamated zinc powder and electrolyte.
Separators of specially selected materials prevent migration of any solid particles in the
battery.
Insulating and sealing gaskets are moulded of nylon.
Exterior battery surfaces of nickel are used to resist corrosion and to insure good
electrical contact.
The type of electrolyte used with silver oxide batteries determines their rate or current
carrying capability.
Under heavy drains, potassium hydroxide (KOH) electrolyte offers less resistance to the
current flow and
allows the battery to operate at higher efficiency than a sodium hydroxide (NaOH)
electrolyte. At low
drains both electrolytes operate with equal efficiency. This relationship is shown in the
following
diagram:
Silver oxide batteries containing a KOH electrolyte are more difficult to seal than those
containing at
NaOH electrolyte. As a result, NaOH batteries are typically more salt resistant than
It provides up to 40 percent more run time than lithium-ion batteries and also feature a
similar sized KOH
water-based chemistry that is free from the thermal runaway and flammability problems
batteries. Both batteries however, exhibit excellent long term salt resistance.
that have plagued the lithium-ion alternatives
Temperature:
Silver oxide batteries have good performance characteristics at temperature extremes.
They can be
used up to 55°C(131°F). Silver oxide batteries utilizing KOH as an electrolyte will operate
with less loss
of efficiency at lower temperatures than comparable NaOH batteries. Batteries with KOH
electrolyte will
operate down to -28°C (-20°F) and NaOH batteries down to -10°C(14°F) with some This once attractive technology had the highest energy density (prior to lithium
technologies), and was primarily developed for aircraft use. The worldwide rise in silver
service reduction in
prices seemed to spell its demise. It was the power source in all of the Apollo
both types.
spacecraft: the command module re-entry batteries, the lunar module and the lunar
rover. (The Apollo Service Module used fuel cells as a primary power source.)
More recently, the company ZPower has introduced a new line of rechargeable silverApplications:
zinc batteries to compete with lithium-ion batteries. The claims include an energy
Eveready silver oxide batteries are specially designed to meet the varying power
density of 200Wh/kg, complete non-flammability, and no toxic chemicals. To offset the
requirements of a wide
high price of silver, the company plans to offer a trade-in policy to recycle all of it.[2][3]
variety of applications.
Intel's venture arm, Intel Capital, has provided the company with financial backing.[4]
Watch and Calculator - Silver oxide watch batteries using a sodium hydroxide (NaOH)
ZPower claims that an undisclosed "major manufacturer" of laptop computers will
electrolyte
introduce its silver-zinc battery in a new line of laptops in 2009.
system are primarily designed for low drain continuous use over long periods of time,
typically up to five
years. This is commonly found in analog watch applications.
Silver oxide watch batteries using a potassium hydroxide (KOH) electrolyte system are
principally
designed for continuous low drains with periodic high drain pulse demands for periods
of approximately
one to two years. This is typical of applications such as LCD watches with backlight,
analog watches with
alarms and calculators.
Hearing Aid and Electronic - Silver oxide hearing aid and electronic batteries are
designed to
produce greater volumetric energy density at higher continuous discharge rates than
silver oxide watch or
photographic batteries. Hearing aid and electronic batteries use potassium hydroxide
electrolyte in
combination with the separator system designed to match the required application.
Photographic - Silver oxide photo batteries are designed to provide constant voltage or
periodic
high drain pulses with or without a low drain background current.
Silver Oxide Cells The silver oxide cell is really the ideal successor to mercury batteries,
and is superior in a number of ways. It has a higher capacity than mercury cells for a
given size. These cells are rated at 1.62 volts. Their construction is very similar to
mercury cells, the cathode material being the main difference.
Advantages
Constant voltage over its useful life. Contains no chemicals harmful to the environment.
Basically superior in all ways over mercury cells.
Disadvantages
About half the shelf life of mercury cells.
Uses
Main applications are in watches. Great for Accutrons, which will perform equally well
with these cells as mercury cells.
A) Cell top (-ve electrode)
B) Anode of powdered zinc + electrolyte gel
C) Nylon seal
D) Electrolyte
E) Cathode of Silver Oxide and Graphite
F) Absorbent separator of fabric and electrolyte
G) Barrier separator membrane.
H) Cell Can (+ve electrode)
I) Metal sleeve to support the nylon case seal
THE LITHIUM CELL
Lithium Cells Lithium cells are often called "coin cells" due to their shape. The lithium
cells used in watches are Lithium-Manganese Dioxide, and are rated at 3.0 volts. The
other type of lithium cells commonly seen are Lithium-Thionyl Chloride, which are rated
at 3.6 or 3.7 volts. These are not used in watches.
Advantages
Fairly constant voltage over most of its useful life. Contains no chemicals harmful to the
environment. Very long shelf life, up to 10 years.
Disadvantages
Suitable for low drain or only intermittent high drain applications.
Uses
Excellent for quartz watches that draw very low current, and only intermittent current
when the stepper motor is driven. Can last 5 years or more in the correct application.
Not suitable for Accutrons as the voltage is too high.
A) Cell top (-ve electrode)
B) Anode of lithium
C) Nylon seal
D) Electrolyte in Separator, Anode and Cathode Material.
E) Cathode of Manganese Dioxide
F) Absorbent separators containing electrolyte
G) Cell Can (+ve electrode)
Zinc-Air Cells
Note: Not to be used in watches!
Zinc-Air cells are not watch batteries, and are included in this list because they seem at first
glance to be a good alternative to Mercury cells for our Accutrons. Read on and find out why
not. Zinc-Air cells have the highest capacity of all button cells due to the fact that most of
the cell volume can be taken up with anode material (zinc), because the cathode material
used is oxygen obtained from the atmosphere. Their rated voltage is 1.4 volts. They are
activated by peeling off an adhesive layer, allowing air to enter the cell through small vent
holes.
Advantages
Very high capacity for their size. Very constant voltage ouptut for most of their life. Able to
be used in medium current applications. Slightly shorter shelf-life than Mercury cells when
not activated, but longer than Alkaline and Silver Oxide. Environmentally safe.
Disadvantages
Must be used in applications where the battery compartment is vented to the atmosphere.
The cells are hygroscopic, and therefore may store and release water to and from the
atmosphere. Actual performance of the cell can depend on the relative humidity.
Uses
The main use for Zinc Air button cells is in hearing aids. They must not be used in watches,
as they require atmospheric oxygen to function, and they may emit water which can be
corrosive to metal parts. Under extremes of temperature, or if the cell is shorted out, the
internal membranes may rupture, and vent liquids and gas to the atmosphere. Do not use in
watches!!!
THE ALKALINE CELL
Type
Primary
Chemical Reaction
2Zn + 3MnO2
Operating Temperature
-20º F to 130º F ( -28º C to 54º C). Good range of operating temperatures.
Recommended for
High-discharge devices, which include (but are not limited to): Digital cameras, RC cars,
portable power tools, heavy-use flashlights, CB walkie-talkies, FRS radios, portable
televisions, handheld video games, portable audio systems (such as boomboxes), CD
players, MP3 players, appliances, shavers, and toothbrushes.
Initial Voltage
1.5 volts or 9.0 volts.
Capacity
•When used in a device with a high discharge rate, the service life is up to 38% higher than
standard alkalines.
•At low to moderate discharge rates, performance is similar to standard alkalines.
•Alkaline batteries do not have a standard capacity rating; see the Capacity heading for a
full explanation.
Discharge Rate
Sloping. Products with a high current drain are particularly hard on batteries; the higher the
current drain is, the steeper the discharge slope will be.
Internal Resistance
Very low. It remains almost constant until the end of its life when it will increase rapidly.
Impedance
Very low (much less than that of carbon zinc batteries).
Storage Life
Loses 5% of performance after one year, and 2.5% each year after. We recommend that
these be used within
5 years.
Initial
Voltage
Storage Temperature
-40º F to 120º F ( -40º C to 48º C).
KOH-->
2ZnO + MN3O4
Chemical Reaction
Operating Temperature
2Zn + 3MnO2
KOH-->
2ZnO + MN3O4
See each type.
1.5 volts or 9.0 volts.
Capacity
Alkaline batteries do not have a standard capacity
rating; see the Capacity heading for a full
explanation.
Discharge Rate
Sloping. Products with a high current drain are
particularly hard on batteries; the higher the current
drain is, the steeper the discharge slope will be.
Internal Resistance
Very low. It remains almost constant until the end of
its life when it will increase rapidly.
Impedance
Very low (much less than that of carbon zinc
batteries).
Storage Life
See below.
Storage Temperature
See below.
Disposal
Not recyclable; can be safely thrown away.
Positive cap: Formed protrusion at one end of the battery can which identifies it as the
positive terminal.
Steel can: Nickel-plated steel which is formed into a container to hold chemicals and
serves as the positive collector.
Outer Jacket: A plastic sleeve which contains decorative printing identifying the cell
type and size.
Separator: Porous non-woven fibrous material which separates electrodes; holds
electrolyte between electrodes.
Electrolyte: A solution of potassium hydroxide in water which carries the ionic current
inside the battery.
Cathode: Manganese dioxide and graphite which take up electrons from the external
circuits.
Anode: Powdered zinc metal which serves as the source of electrons.
Anode Collector: Tin-plated brass which serves as a path for the electrons from the
anode to the external circuit.
Seal/Vent: Molded plastic disc which holds internal components inside the cell and
releases internal pressure when battery is abused.
THE LITHIUM IRON DISULFIDE
CELL
Lithium-Iron:
A recent addition in the marketplace, the Lithium Anode, Iron Sulfide (or Iron Disulfide)
Cathode battery stands out from the rest of the Lithium based Primary batteries in that
its voltage output is typically 1.5 volts and comes in standard AA size. It also has for a
Primary Lithium based battery uncommonly high capacity and high drain characteristics,
typically higher than normal Zinc Manganese Dioxide Alkaline batteries. However their
cost, when compared with normal Alkaline batteries has to be taken into consideration,
especially when a lot of the simpler silent Super 8 cameras tend to have low to moderate
drain characteristics.
BUTTON
Lithium-Manganese Dioxide:
The most commonly available Lithium based button cell type battery, it consists of a
Lithium Anode, Manganese Dioxide cathode and typically an organic electrolyte. It,
however, cannot be used for replacing a Mercury Oxide battery because of its size,
voltage (typically 3 volts) and its sloping output voltage characteristic under mid to high
drain applications.