Which Battery Lasts The Longest In A Flashlight?

The flashlight is one of the appliances we need at our home. It is very useful to provide light during a blackout. It is also very common to use this device when we are going to check on something that requires extra light. To make sure that it can function properly, we just need to make sure that the batteries we put into the flashlight are still working.

As one of the mush-have item in every home, we need to know that the flashlight can be used properly every time we need it. That is why we have to get enough information about which battery lasts the longest in a flashlight. That way we can buy the brand that has the best durability.

It is simple to check which battery lasts the longest in a flashlight. You can do this experiment at home with materials that you can easily find at home. If you do not have one of the materials, you can buy it in any supermarket.


The Best Battery for Your Flashlight

Every battery brand claims that their brand is the best one. Each of them advertises their product as the most long-lasting one. We can find out which one of some of the popular battery brands that can last the longest in a flashlight.

Here are the materials, instructions, and the information about the experiment you are going to do at home.


  • Three pieces of flashlights. All of them must have the same type, size, brand, and take D-size batteries.
  • Popular battery brands: Duracell, Energizer, and Eveready. You need to provide two pieces of each in D-size.
  • Label
  • Marker
  • Notebook
  • Timer/clock

In this experiment, we use the flashlights as the constant variable, which means we set the same condition for all three different battery brands. We are going to observe the battery that lasts the longest in a flashlight. So, we use brands that people are familiar with.

These brands have different prices so we are going to discover if there is a correlation between the price of the battery and its endurance. Another thing that we are going to know is if the type of battery affects its ability to last. Among the three brands, Eveready is the only non-alkaline batteries, while the other two are alkaline.


  1. Write each brand in three pieces of the label. Stick the label on the flashlight.
  2. Put two batteries into each of the flashlights accordingly with the brand name on the label.
  3. Turn on the flashlights at the same time. Make sure you to write the time on your notebook.
  4. In the beginning, you can also note in your notebook if there is a particular brand that shines the brightest.
  5. Every hour you can make a note of which brand is getting dimmer.
  6. Observe each of the brands and when the batteries are dead, make sure to write down the time.

The whole experiment can take you almost a full day (24 hours). To make it easier for you to do the observation, you can start early in the morning. Since you are going to check the intensity of the brands on an hourly basis, you must ensure that you have a clear schedule during the day of your experiment. That way you will not have any distractions.



Among the three brands, Duracell is the most expensive and Eveready are the cheapest. Duracell D-size batteries can cost you up to six times the price of Eveready! But the result shows that the price has nothing to do with the quality of the battery.

Based on this experiment, a battery that lasts the longest in a flashlight is Energizer. It lasts for 22 hours and 15 minutes. On the second place is Duracell. It takes 115 hours until the Duracell batteries to not work anymore and in the last place is Eveready which lasts for 6 hours and 35 minutes.


Another conclusion of this experiment is alkaline batteries last longer than non-alkaline batteries. This is supported by the fact that alkaline batteries have more capacity than the non-alkaline ones so when applies in the same device, the one with alkaline will work longer than the one with non-alkaline batteries.

  • Further Experiment

We do not include another factor, such as the expired date of the batteries, into this experiment. In the future scientific project, you can insert this factor to see whether the fresher the batteries, the longer it lasts.

Now we know that the battery from the brand Energizer is the one that lasts the longest in a flashlight. Next time you want to stock or buy fresh batteries for your flashlight, you know the best brand to choose!