Purchase the same flashlights for each set of batteries you wish to include in this experiment. Choose a number of battery brands, and purchase the needed flashlight batteries from each. Load the batteries into the flashlights, and label each flashlight with the brand of batteries being used in it. Be sure to turn each flashlight on at the same time. You may need additional people to accomplish this. Note the time the flashlights are turned on, and leave them on overnight. Check on them the next day, and begin recording the time they dim out or go dark.
To keep the parameters simple, use the same flashlights from the overnight brand test. Insert fully charged rechargeable batteries in one flashlight and new batteries into another flashlight. If you want to expand the outcome of the experiment, include new batteries from several brands to determine which brands may or may not outlast rechargeable batteries. Again, note the time the flashlights are turned on and monitor the flashlights to see when each one dims.
Not all batteries are made of the same materials. By purchasing batteries of the same size but made of the varying materials on the market, you can test to see which performs the best. Purchase batteries of the following types: alkaline, non-alkaline, nickel cadmium, nickel-metal hydride and carbon-zinc. Again, load these into the flashlights and test performance using the same method as in the brand test. Record the time the flashlights are turned on and record the time the flashlights dim out.
While it is interesting to note which brand and materials type last the longest, the bottom line for consumers is which battery is the best buy. By keeping your receipts and using the purchase cost divided by the number of hours each battery lasted, you can determine which battery is the best buy.