A battery is a source of
electrical energy, which is provided by one or more electrochemical cells of
the battery after conversion of stored chemical energy. In today’s life,
batteries play an important part as many household and industrial appliances use
batteries as their power source.
Batteries can be divided into
two major categories, primary batteries and secondary batteries. A primary
battery is a disposable kind of battery. Once used, it cannot be recharged.
Secondary batteries are rechargeable batteries.
Once empty, it can be recharged again. This charging and discharging can happen
many times depending on the battery type. Alkaline batteries, Mercury
batteries, Silver-Oxide batteries, and Zinc carbon batteries are examples of
primary batteries whereas Lead-Acid batteries and Lithium batteries fall into
the secondary battery's category.
Alkaline batteries are
non-rechargeable, high energy density, batteries that have a long life span.
This battery obtained its name because the electrolyte used in it is alkaline
(potassium hydroxide). The chemical composition features zinc powder as an
anode and manganese dioxide as the cathode with potassium hydroxide as the
electrolyte.
The chemical reactions are:
Zn (s) + 2OH− (aq)
→ ZnO (s) + H2O (l) + 2e−
2MnO2 (s) + H2O (l) +
2e− →Mn2O3 (s) + 2OH− (aq)
If we compare the capacity of
an alkaline cell with a zinc-chloride cell of same size, the former can provide
about four to five times more energy under equal load conditions. The supply
voltage level decreases over time so the minimum required voltage level for a
particular load may not match the supplied voltage level and thus results in no
operation. But the rate of decline of alkaline batteries is lower than the
Leclanche cell, thus longer life. The typical values of voltage and current
supplied by a single alkaline cell are 1.5V and 700mA respectively. These
batteries are distributed in various standard cylindrical shapes.
Applications
Alkaline batteries are the
most common type of batteries used in the world with major consumption in the
US, UK and Switzerland. Designed for long lasting performance, these can be
found in remote controls, clocks, and radios. The high run time makes alkaline
batteries ideal for digital cameras, hand held games, MP3 players etc.
Zinc-Carbon batteries are also
known as dry cells (as the nature of electrolyte used in these cells is dry),
which come in a composition of a carbon rod (cathode) surrounded by a mixture
of carbon powder and manganese dioxide (to increase the conductivity). This
whole combination is packed in a zinc container acting as the anode. The
electrolyte is a mixture of ammonium chloride and zinc chloride. The typical
voltage value is a little less than 1.5V. These batteries are durable and have
longer lives. Zinc-Carbon batteries can be used effectively at moderate
temperature but do not work well at low temperatures.
Applications
These general purpose
batteries are available for lower prices which is why many electronic devices
are sold with these batteries included free. The basic use is in low power
drain applications such as flash lights, remote controsl, toys, and table
clocks.
Lead-acid batteries are the
rechargeable kind of batteries invented in the 1980s. These large, heavyweight
batteries find the major application in automobiles as these fulfill the high
current requirements of the heavy motors. The composition of Lead-Acid battery changes in charged and discharged
states.
A combination of Pb (negative)
and PbO2 (positive) as electrodes with H2SO4 as electrolyte in charged form and
PbSO4and water in discharged form.
Applications
The major application of lead acid battery
is in starting, lightning, and ignition systems(SLI) of automobiles. Its other
form, wet cell battery is used as backup power supply for high end servers,
personal computers, telephone exchanges, and in off grid homes with inverters.
Portable emergency lights also use lead acid batteries.
Mercury batteries are
non-rechargeable batteries that contain mercuric oxide with manganese dioxide.
They are deep discharge batteries and voltage level does not fall below 1.35V
until 5% energy level is reached. These batteries are less popular because of
low output voltage. Furthermore, mercury is toxic and can cause hazards for humans.
Applications
The flat discharge curve makes
this battery useful for photographic light meters and electronic devices such
as to run the real-time clock of CPU.
Lithium batteries are
rechargeable (secondary) batteries, where lithium in its pure ion compound form
is used. Depending on the design and chemical compounds used, lithium batteries
can produce voltages from 1.5 Volts to 3.7 Volts. The most common type of
lithium battery used in consumer applications uses manganese dioxide as cathode
and metallic lithium as anode. Compared to ordinary zinc–carbon batteries or
alkaline batteries, the voltage production of lithium cell is twice from them.
Silver oxide batteries are
expensive, small to large sized primary cells that offer better run time than
alkaline batteries. They are usually suitable for powering low-current
electrical devices.They use silver oxide as positive (cathode) electrode, zinc
as negative (anode) electrode plus alkaline electrolyte, normally Potassium
hydroxide (KOH) or Sodium Hydroxide (NaOH).
Applications
These long life batteries are
used in portable consumer instruments like calculators, iPods, digital diaries,
wrist watches and stop watches, toys, and artificial pacemakers. Lithium cells
can also be used as a replacement of alkaline batteries in many devices, such
as cameras and clocks. Although they are more expensive, lithium batteries will
provide much longer life. Silver Oxide batteries are used in military and
submarines.
From alkaline batteries to
silver-oxide, the different types of batteries are used in different
applications.