Which Brand of Batteries Is Stronger or Lasts Longer?

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Talk It Over

Some brands of batteries advertise that they are stronger or last longer than other brands. How can you test their claim?


  • 2 identical flashlights with new bulbs
  • 2 different brands of batteries, new, of the right size for the flashlights
  • Large, felt-tip marker
  • Electrical tester*
  • Watch or clock
  • Sunprint Kit (optional for "Go Far")*


  1. Start this experiment in the morning, so you can work on it all day if you need to. Make sure all your batteries are new and fresh. Check the expiration dates printed on the packages.
  2. Using the marker, put a letter on the side of each battery. Letter them A, B, C, D, and so on.
  3. Following the manufacturer's directions for the electrical tester, check the output of each battery. Record the numbers in a table.
  4. Load the batteries in the flashlights, using a different brand for each flashlight. Note the letters on the batteries you put in each flashlight and the order you put them in (because most flashlights require more than one battery).
  5. Switch on the flashlights and note the time. Allow them to burn for 30 minutes.
  6. Turn off the flashlights. Remove the batteries and test each with the electrical tester. Record the time and the reading.
  7. Return the batteries to their same flashlights and same positions. Let them burn for another 30 minutes. Then turn off, remove, remeasure, and reload. Keep doing this every 30 minutes for several hours.

Stay Safe

The batteries can't hurt you. The amount of electricity they discharge is too small. Flashlights' bulbs can, however, get hot. Pick up flashlights only by their handles.

Go Easy

The "Go" procedure will work for you.

Go Far

Use the "Go" procedure to test several different brands. Test each brand three times and average your results.

You can improve your project with pictures that show differences in the intensity of the lights at different times. If, for example, you notice that 1 light is looking dimmer than another at 11:30 a.m., do this:

  1. Turn off the flashlights.
  2. On a table close to a wall, place the flashlights at least 60 cm (2 feet) apart.
  3. In front of each flashlight, tape to the wall a piece of light-sensitive paper from a Sunprint Kit*.
  4. Move the flashlights close to the paper. Their light should be no more than 1 cm (less than ½ inch) from the wall.
  5. Turn the flashlights on. Let them shine on the paper for 30 minutes or more. (You may need to try this several times, using more or less time. The time depends on how bright the lights are.)
  6. Process the photosensitive paper in water as the package directs.
  7. The brighter the light, the darker the circle that appears on the paper.
  8. To get numbers that will allow you to compare the lights, make a black-and-white photocopy of your papers. (Set the copy machine to make a light copy.) Then find the numbers on your grayscale (See "How to Make a Grayscale" in Part III) that most closely match the dark spots your flashlights made on the paper. The higher the number, the brighter the light was.
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