You can't always believe what the advertising tells you. And when it comes to batteries, it's easy to become confused as to which is the best battery for the price. You don't have to trust in the ads anymore. Stop paying top price for a second-rate product. You can do this simple experiment and find out for yourself. With all of the toys, flashlights, portable radios and other devices that rely on battery power, making certain that you get the best battery for the price will not only save you lots of money, but will help to avoid the need to constantly change batteries to keep those device working.

In a battery powered device such as a flashlight, the batteries are the power source that converts chemical energy to electrical energy using a cathode, an electrolyte, and an anode. The cathode is normally a metallic oxide. The electrolyte is an electricity conductor. The anode is a metal. They must be able to attract electrons to generate an electric current.

When you turn on a device, such as a flashlight, an electric current created in the battery is what powers that device. The electrical current, in the form of electrons is created from the anode material, zinc, which gives up two electrons per atom in a process called oxidation.

Batteries come in many shapes and sizes. Some are no larger than a pill while others are too heavy to lift. But most batteries have one thing in common - they store chemical energy and convert it into electrical energy.

The cell is the basic unit that produces electricity. A battery has 2 or more cells, but people often use the word battery when talking about a single cell like a dry cell. A dime-sized battery in a watch is a cell. Cells act like pumps to force electrons to flow along conductors.

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 kind of cell has a particular EMF. A dry cell, for example, has an EMF of 1.5 volts.

Another way to measure a battery is by how much electric current it can provide. Electrical current is measured by how many electrons flow through the cell. The unit used to measure electrical current is amps.

The most common cell is the dry cell and different types have different types of electrolytes. 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.

Most flashlights take two or more dry cells. Cells are connected in a 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 lifetime, in a sense providing better quality.

A high powered device, such as a motorized toy running constantly, requires more current than a less power hungry device, such as a personal stereo, that alternately runs and rests. Batteries also don't perform as well at low temperatures. As you use a battery, its EMF drops. You can consider an alkaline battery dead at 0.9 volts.

In order to work well in high drain devices, the shell of the battery needs to be made thinner so it can hold more electrons and deliver more current. Companies have made improvements in their batteries to increase performance in high drain devices. A high drain device is an object that requires a lot of current. Low drain devices would include CD and cassette players and related devices.

In order to do your experiment you will need certain materials such as a CD player & CD (low drain device), three identical flashlights (medium drain device), a camera flash (high drain device), AA size batteries of any other brand you wish to test, AA size of a heavy duty (non alkaline battery), a voltmeter and AA battery holder and a kitchen timer.

You are now ready to proceed with your winning science fair project and here's how to do it.

1.Number each battery so you can tell them apart.

2.Measure each battery's voltage by using the voltmeter.

3. Put the same battery into one of the devices and turn it on.

4. Let the device run for sixty minutes before measuring its voltage again. (Record the voltage in a table every time it is measured.)

5. Repeat #4 until the battery is at 0.9 volts or until the device stops.

6. Repeat steps 1-5 again: three trials for each brand of battery in each experimental group.

7. For the camera flash test, push the flash button every 30 seconds and measure the voltage every 5 minutes.

8. For the flashlight test, rotate each battery brand so each one has a turn in each flashlight.

9. For the CD player, repeat the same song at the same volume throughout the tests.

Which batteries performed the best? Make a comparison of the prices you paid vs. the efficiency of the battery and you will know for yourself which is the best deal on the market.