Power in pocket

How does the battery in your phone or the flashlight work?

Santosh Kushwaha        Print Edition: December 2011

Batteries are a portable source of electricity-an absolute necessity in these days of devices that ride in your pocket or your purse. Some batteries are disposable, others are rechargeable, but all batteries work on a similar mode. A battery has a positive and a negative electrode, the first called a cathode and the other called an anode. Electrons move between these two to create a current. In batteries, each electrode consists of a different metal.

For instance, in an alkaline battery, the anode metal is manganese dioxide, while the metal in the cathode is zinc. Separating the anode from the cathode is an electrolyte which allows the passage of electrons. The negatively charged ion (anion) naturally tends to migrate towards the anode, while the positively charged cation moves towards the cathode. To power a light, for example, the ions go though a circuit, power the light and arrives at the positive ends of the battery.

When you recharge a battery, you change the direction of the flow of electrons using a power source, such as electricity or solar panels. The electrochemical processes happen in reverse, and the anode and cathode are restored to their original state and are ready to again provide full power.

Non-rechargeable batteries, or primary cells, and rechargeable batteries, or secondary cells, produce current exactly the same way: through an electrochemical reaction involving an anode, cathode and electrolyte. In a rechargeable battery, however, the reaction is reversible. When electrical energy from an outside source is applied to a secondary cell, the negative-to-positive electron flow that occurs during discharge is reversed, and the cell's charge is restored. The most common rechargeable batteries on the market today are lithium-ion (Li-Ion).

1748: Benjamin Franklin first coined the term "battery" to describe an array of charged glass plates.

1780 to 1786: Luigi Galvani demonstrated what we now understand to be the electrical basis of nerve impulses and provided the cornerstone of research for later inventors like Volta to create batteries.

1859: French inventor, Gaston Plante developed the first practical storage lead-acid battery that could be recharged (secondary battery). This type of battery is primarily used in cars today.

1866: French engineer Georges Leclanche patented the carbon-zinc wet (that is, with a liquid electrolyte) cell battery called the Leclanche cell.

1881: Carl Gassner invented the first commercially successful dry cell battery (zinccarbon cell).

1899: Waldmar Jungner invented the first nickelcadmium rechargeable battery

Courtesy:Gadgets and Gizmos

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