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.

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.

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

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.