Science Fair

Batteries come in many shapes and sizes. Some are no larger than a pill while others are heavy and huge size, but most batteries have one thing in common. They store chemical energy and change it into electrical energy. The cell is the basic unit producing electricity. A battery has 2 or more cells, but people often use the world battery when talking about a single cell, too, like a dry cell. One of the most popular batteries that have a cell is a dime sized battery which we use for watches. Cells force electrons to flow along conductors.(DK Science 150).

"The electrical force of a cell or battery is called its electromotive force (emf). This force, which makes electrons flow around a circuit, is measured in units called volts (v). Each king of cell has a particular emf. A dry cell, for example, has an emf of 1.5volts." (DK science 150)

The other way to measure a battery is by how much current it can provide. Current is used to measure how many electrons flow through the cell and amp is the basic unit for current.

There are lots of important parts for regular batteries. They are the positive terminal and electrode, the negative terminal and electrode, and the electrolyte which is located between the two electrodes. The positive electrode is made out of a carbon rod. Powdered carbon and manganese oxide prevents hydrogen from forming on the carbon rod, which would stop the cell from working normally. For the negative electrode, Zinc is used, which serves, as a case for the cell. Electrons flow from the negative terminal through a wire in the device the battery is powering into the positive terminal (learning center).

The most common cell is the dry cell and different types have different types of electrolytes. The dry cell works like the cell invented by the French engineer Georges Leclanceh in 1865. His cell had a liquid electrolyte, but in the modern version the electrolyte is ammonium chloride paste(DK Science 150). Ordinary dry cells are used in most flashlight batteries. These dry cells use ammonium chloride as the electrolyte. "Cells needed to supply heavier currents use zinc chloride. Alkaline cells, which last longer and can supply even heavier currents, use the alkali potassium hydroxide" (DK Science 150).

The earliest method of generating electricity occurred by creating a static charge. In 1660, Otto von Guericke constructed the first electrical machine that consisted of a large sulfur globe which, when rubbed and turned, attracted feathers and small pieces of paper. Guericke was able to prove that the sparks generated were truly electrical. The first suggested use of static electricity was the so-called "electric pistol". Invented by Alessandro Volta, an electrical wire was placed in a jar filled with methane gas. By sending an electrical spark through the wire, the jar would explode (Battery History 12).

Based on what chemical elements are used, there are several types of batteries and each type of batteries has their own specialized characteristics.

Nickel-Cadmium has been the most common space battery since the 70's. They were used in all commercial communications satellites, in most earth orbiters, and in some space probes. They are generally a prismatic (resembling, or being a prism) design, and packaged very efficiently. This means that the batteries can be stored on the spacecraft in a very compact form, eliminating the need for extraneous space. They have been known to last for ten to twenty years in space. They are still in use in selected space applications, including small satellites and for missions that encounter very severe radiation environments.

The Nickel-Hydrogen battery is currently the most popular space battery. It can be considered a hybrid between the nickel-cadmium battery and the fuel cell. The cadmium electrode was replaced with a hydrogen gas electrode. This battery is visually much different from the Nickel-Cadmium battery, because the cell is a pressure vessel, which must contain over one thousand pounds per square inch (psi) of hydrogen gas. It is significantly lighter than nickel-cadmium, but is more difficult to package, much like a crate of eggs. It is the longest-lived space battery yet built, with 10 to 20 year lifetimes being common. This battery is too expensive for commercial applications, and few terrestrial examples have been built.

Lithium Batteries are different from all of the previously mentioned batteries, in that no water is used in the electrolyte. They use a non-aqueous electrolyte instead, which is composed of organic liquids and salts of lithium to provide ionic conductivity. This system has much higher cell voltages than the aqueous electrolyte systems. Without water, the evolution of hydrogen and oxygen gases is eliminated and cells can operate with much wider potentials. They also require a more complex assembly, as it must be done in a nearly perfectly dry atmosphere.

Most flashlights take two or more dry cells. Cells are connected in series one after another. Large powerful flashlights may take four or more cells. The size of a cell has no effect on its emf. The chemicals in the cell determine its emf, but large cells last longer than small cells of the same basic type.

How long a battery lasts also depends on how it's used. Two batteries may last the same length overall but one might maintain higher voltage over more of its lifetimes, in a sense providing