Note:

This is an actual project that won first place in the Physics and Electricity category at a 6th grade science fair. Some science fairs prohibit product comparisons like this because students often perform them in an "un-scientific" manner. This project did not fall into that trap. The student scientist asked a simple question, but backed it up with excellent background research so that she could evaluate the products scientifically. She established three experimental groups, found a dependent variable that she could numerically and precisely measure, established good controlled variables, formulated an excellent hypothesis, collected lots of data in repeated trials, produced excellent graphs of her results, and reached a solid conclusion. In the process she learned about problem solving using the scientific method, not to mention a lot about batteries. [Note: This student's teacher did not require source citations and required a different format for the bibliography. Science Buddies staff added references and reformatted the bibliography at a later date; consequently, the page and volume references are fictitious for some of the sources.]

Table of Contents

Abstract

Objective:
My objective was to determine which AA battery maintains its voltage for the longest period of time in low, medium, and high current drain devices.

Materials and Procedures

Materials Used

• CD player & a CD (low drain device)
• Three identical flashlights (medium drain device)
• Camera flash (high drain device)
• AA size Duracell and Energizer batteries
• AA size of a "heavy-duty" (non-alkaline) battery (I used Panasonic)
• Voltmeter & a AA battery holder
• Kitchen timer

Procedure

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 thirty 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. Do steps 1-5 again, three trials for each brand of battery in each experimental group.
7. For the camera flash push the flash button every 30 seconds and measure the voltage every 5 minutes.
8. For the flashlights 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.

Results
According to my experiments, the Energizer maintained its voltage (dependent variable) for approximately a 3% longer period of time (independent variable) than Duracell in a low current drain device. For a medium drain device, the Energizer maintained its voltage for approximately 10% longer than Duracell. For a high drain device, the Energizer maintained its voltage for approximately 29% longer than Duracell. Basically, the Energizer performs with increasing superiority, the higher the current drain of the device.

The heavy-duty non-alkaline batteries do not maintain their voltage as long as either alkaline battery at any level of current drain.

Conclusions/Discussion
My hypothesis was that Energizer would last the longest in all of the devices tested. My results do support my hypothesis.

I think the tests I did went smoothly and I had no problems, except for the fact that the batteries recover some of their voltage if they are not running in something. Therefore, I had to take the measurements quickly.

Question and Hypothesis

Question
Which AA battery maintains its voltage for the longest period of time in low, medium, and high current drain devices?

Hypothesis
My hypothesis is that the AA Energizer will maintain its voltage (dependent variable) for the longest period of time (independent variable) in low, medium, and high current drain devices, tested with the controls described in the problem statement.

Review of Literature

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 change 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, too, 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 (DK Science 1998, 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 kind of cell has a particular emf. A dry cell, for example, has an emf of 1.5 volts" (DK Science 1998, 150).

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

A common cell has several important parts: the positive terminal and electrode, the negative terminal and electrode, and the electrolyte, which is 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. The negative electrode is made out of zinc, 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 1999).

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 Leclanche in 1865. His cell had a liquid electrolyte, but in the modern version the electrolyte is ammonium chloride paste (DK Science 1998, 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 1998, 150).

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 lifetime, in a sense providing better quality. A high powered device such as a motorized toy running constantly takes 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 (Best Batteries 1994, 71).

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 you need to make the shell of the battery thinner so it can hold more electrons and deliver more current (Booth 1999, 127).

Companies have made improvements in their batteries so they are better in high drain devices. A high drain device is a thing that takes a lot of current. Low drain devices would include CD and cassette players and related devices. "Eveready meanwhile quantifies the power requirements as 400 to 800 mA for halogen lamps; 400-1000 mA for cellular phones; and 500-900 mA for camcorders. Digital cameras are in the 800-1200 mA range, while photoflash units are the thirstiest of all-1000 to 2000 mA according to Eveready" (Booth 1999, 127).

Materials and Procedure

Materials Used

• CD player & a CD (low drain device)
• Three identical flashlights (medium drain device)
• Camera flash (high drain device)
• AA size Duracell and Energizer batteries
• AA size of a "heavy-duty" (non-alkaline) battery (I used Panasonic)
• Voltmeter & a AA battery holder
• Kitchen timer

Procedure

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 thirty 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. Do steps 1-5 again, three trials for each brand of battery in each experimental group.
7. For the camera flash push the flash button every 30 seconds and measure the voltage every 5 minutes.
8. For the flashlights 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.

Results

According to my experiments, the Energizer maintained its voltage (dependent variable) for approximately a 3% longer period of time (independent variable) than Duracell in a low current drain device. For a medium drain device, the Energizer maintained its voltage for approximately 10% longer than Duracell. For a high drain device, the Energizer maintained its voltage for approximately 29% longer than Duracell. Basically, the Energizer performs with increasing superiority, the higher the current drain of the device.

The heavy-duty non-alkaline batteries do not maintain their voltage as long as either alkaline battery at any level of current drain.

Conclusion

My hypothesis was that Energizer would last the longest in all of the devices tested. My results do support my hypothesis.

I think the tests I did went smoothly and I had no problems, except for the fact that the batteries recover some of their voltage if they are not running in something. Therefore, I had to take the measurements quickly.

An interesting future study might involve testing the batteries at different temperatures to simulate actual usage in very cold or very hot conditions.

Acknowledgments

I would like to thank my teacher Mrs. Garmon, and my father who let me take over his workshop while I worked on my experiment.

Bibliography

"Battery." Encyclopedia Britannica. 1990.

"Best Batteries." Consumer Reports Magazine 32 (December 1994): 71-72.

Booth, Steven A. "High-Drain Alkaline AA-Batteries." Popular Electronics 62 (January 1999): 58.

"Cells and Batteries." The DK Science Encyclopedia. 1993.

"Fun Learning." The Gillette Company. [cited January 24, 1999]. www.duracell.com/Fun_Learning/index.html.

"Learning Center." Eveready Battery Company, Inc. [cited January 24, 1999]. www.energizer.com/learning/default.asp.

Table and Figures

[Note: This table is only one of many completed for this project. The graph is one of three that the student prepared.]

 

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