BATTERIES
There are many kinds of batteries which consist of
different materials in order to produce an electric charge. Here are some of the
most common batteries, what they consist of and how they work.
Bichromate Cell (see picture # 1)
A battery is a device which
converts chemical energy into electrical energy. A battery usually consists of
two or more cells connected in series or parallel, you can also have a single
cell battery. All cells consist of a positive electrode, and a negative
electrode. An electrolyte is a liquid substance capable of conducting
electricity. In this substance one of the electrodes will react producing
electrons, while the other will except electrons. When the electrodes are
connected to a device to be powered, called a load, an electrical current flows.
Batteries where the chemicals cannot be returned to their original form once
the energy has been converted (that is, batteries that have been discharged) are
called primary cells or voltaic cells. Batteries in which the chemicals can be
returned to its original form by passing an electric current through them in the
direction opposite that of normal cell operation are called secondary cells,
rechargeable cells, storage cells, or accumulators.
Dry Cell Battery(see
picture # 2)
This is the most common battery that people use today like
Energizer or Duracle batteries. The most common form of a primary cell is the
Leclanche cell, invented by a French chemist Georges Leclanche in the 1860s. The
electrolyte for this battery consisted of a mixture of ammonium chloride and
zinc chloride made into a paste. The negative electrode is zinc, and is the
outside shell of the cell, and the positive electrode is a carbon rod that runs
through the center of the cell. This rod is surrounded by a mixture of carbon
and manganese dioxide. This battery produces about 1.5 volts.
Another widely
used primary cell is the zinc-mercuric-oxide cell, more commonly called a
mercury battery. It can be made in the shape of a small flat disk and is used in
this form in hearing aids, and electric wristwatches. The negative electrode
consists of zinc, the positive electrode is of mercuric oxide, and the
electrolyte is a solution of potassium hydroxide. The mercury battery produces
about 1.34 volts.
The fuel cell is another type of primary cell. It is
unique in that the chemicals aren\'t contained within the cell but are supplied
from outside of the cell.
Secondary Cells
Lead-Acid Storage Battery
(see picture # 3)
The lead-acid storage battery is most commonly used in
automobiles, trucks, aircraft, and other vehicles. The storage battery or
secondary cell, which can be recharged by reversing the chemical reaction, was
invented in 1859 by a French physicist named Gaston Plante. His cell was a
lead-acid battery, the type widely used today. The lead-acid battery commonly
consists of three or six cells. Its chief advantage is that it can deliver a
strong current of electricity for starting an engine; however, it runs down
quickly. The electrolyte is a diluted solution of sulfuric acid. The negative
electrode consists of lead, and the positive electrode of lead dioxide. In
operation, the negative lead electron breaks into free electrons and positive
lead ions. The electrons travel through the external electric circuit, and the
positive lead ions combine with the sulfate ions in the electrolyte to form lead
sulfate. When the electrons reenter the cell at the positive lead-dioxide
electrode, then another chemical reaction occurs. The lead dioxide combines with
the hydrogen ions in the electrolyte in with the returning electrons to form
water, releasing lead ions in the electrolyte to form additional lead sulfate.
A lead-acid storage cell runs down as the acid slowly is converted into
water and the electrodes are converted onto lead sulfate. When the cell is being
recharged, the chemical reactions described above are reversed until the
chemicals have been restored to their original condition. A lead-acid battery
has a useful life of about four years. It produces about 2 volts per cell.
Recently, lead-acid batteries with useful lives of 50 to 70 years have been
developed for special needs.
Another widely used secondary cell is the
alkaline cell, or nickel-iron battery, developed by the American inventor Thomas
Edison in the early 1900s. The principle of operation is the same as in the
lead-acid cell except that the negative electrode consists of iron, the positive
electrode is of nickel oxide, and the electrolyte is a solution of potassium
hydroxide. The nickel-iron cell has the disadvantage of giving off hydrogen gas
during charging. This battery is used principally in heavy industrial
operations. This battery has a useful life of about ten years and produces about
1.15 volts.