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Silver-Oxide Zinc Batteries Ag2O/Zn
System Description
Silver-oxide/zinc alkaline primary battery
is the predominate system of the miniature battery product line. It can be used in
watches, calculators, photoelectric exposure devices, hearing aids, and electronic
instruments.
Its 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°C) for five
years
Available in voltages ranging from 1.5 to 6.0 volts and a variety of sizes.
Battery Construction
Silver oxide batteries are produced with flat circular cathodes and homogeneous gelled
anodes.
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 molded of nylon.
Exterior battery surfaces of nickel are used to resist corrosion and to insure good
electrical contact
Electro-Chemistry
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. 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 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 similar sized KOH batteries. Both batteries
however, exhibit excellent long term salt resistance.
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 service reduction in both types.
Applications
Silver oxide batteries are specially
designed to meet the varying power requirements of a wide variety of applications.
Watch and Calculator -- Silver oxide
watch batteries using a sodium hydroxide (NaOH) electrolyte 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.
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