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Electrical Engineering Principles
EET 212C

J
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• Examples of primary cells include the
Leclanché cell and the mercury cell
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Such a cell has an e
...
f
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5V when new, but this
falls rapidly if in continuous use
due to polarization
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The
Leclanché cell is suitable only for
intermittent use, applications
including torches, transistor
radios, bells, indicator circuits,
gas lighters, controlling switchgear and so on
...


Sizes of dry Leclanché cell
• The following sizes are found commonly on the market
for this category of cells:
1
...

2
...

3
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Size D – The largest size; commonly used in homes to
power AM and FM radio receivers

See link
https://en
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org/wiki/List_of_battery_sizes

Chemical reactions in a dry Leclanché
cell

Features of dry Leclanché cell
•
•
•
•

Inexpensive, widely available
Inefficient at high current drain
Poor discharge curve (sloping)
Poor performance at low temperatures

Wet Leclanché cell
• A mixture of manganese dioxide and
powdered carbon is pressed around
the carbon rod and then enclosed in a
porous pot which the solution can
soak through
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•
The e
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f
...
5
V and the internal resistance of a
normal size cell is 1 Ohm
...
They
were once a majorly used to supply
power to landline telephone installations in remote
areas
...
Side
reactions due to impurities in
the zinc anode increase selfdischarge and corrosion of the cell
...
Its commercial
success is attributable in part to the
development of plastic seals that
have made it possible largely to
dispense with the use of ammonium
chloride
...
The
zinc chloride battery is capable of
greater continuous service than the
zinc-carbon battery, particularly in
motorized devices such as toys
...
In
earlier times it was used in the form of buttonsized cells for hearing aids and watches
...
However, because of its mercury content,
the cell has been relegated to the role of a
standard reference cell—providing an extremely
reliable 1
...


Zinc mercuric oxide battery (Cont’)

Silver Oxide Cell
• A silver-oxide battery uses silver(I) oxide as
the positive electrode (cathode), zinc as the
negative electrode (anode), plus
an alkaline electrolyte, usually sodium
hydroxide (NaOH) or potassium
hydroxide (KOH)
...


Reactions in the Silver Oxide cell

Silver oxide cell (Cont’)

Advantages of Silver Oxide Battery
• Compared with mercury batteries, silver
oxide batteries have a higher operating
voltage
...


Alkaline cell
• In an alkaline battery, the negative electrode
is zinc and the positive electrode
is manganese dioxide (MnO2)
...
The alkaline
electrolyte of potassium hydroxide remains, as
there are equal amounts of OH− consumed
and produced
...

• Alkaline batteries have a high
internal resistance
...

• A defective battery charger can
cause the alkaline batteries to
explode
...


•

•

•

•
•
•

Alkaline batteries have longer shelf life than other
batteries of the chloride type electrolyte batteries
...
This allows the battery to
produce the same energy while lasting longer than
other batteries
...

Costs of an alkaline battery are much lower than
the other more sophisticated ones containing nickel
and cadmium
...

Alkaline batteries function well even at very low
temperatures
...


Uses of alkaline battery
• Usage of alkaline batteries for low-drain
applications offers commendable
performance with very low replacement rate
...

• Low-drain applications dominate the alkaline
battery market

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