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Batteries: The Shocking Truth

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Areas of Science
Time Required
Average (6-10 days)
You should be familiar with, or willing to do background research on, terms like voltage, current, and resistance.
Material Availability
This project requires a multimeter for measuring battery voltage.
Low ($20 - $50)
Only do this project with common "household" batteries like AA or 9 V. Do not use other types like laptop or car batteries unless you have an experienced adult to help you.
Ben Finio, PhD, Science Buddies
*Note: For this science project you will need to develop your own experimental procedure. Use the information in the summary tab as a starting place. If you would like to discuss your ideas or need help troubleshooting, use the Ask An Expert forum. Our Experts won't do the work for you, but they will make suggestions and offer guidance if you come to them with specific questions.

If you want a Project Idea with full instructions, please pick one without an asterisk (*) at the end of the title.


You probably use batteries to power different devices every day, ranging from toys to TV remotes, without giving it much thought. Figure 1, below, shows some common types of batteries. Eventually the batteries will die and you have to replace them with new ones (or recharge them if they are rechargeable batteries). How much do you actually know about how batteries work? This abbreviated project idea will give you some suggestions to investigate how batteries perform in common household devices.
Photo of a double A and nine volt battery
Figure 1. Some common types of batteries (AA and 9 V).

Batteries act as a voltage source for an electrical circuit. An ideal voltage source can hold a constant voltage indefinitely, while providing any amount of electrical current. However, batteries are not an ideal voltage source. Batteries have internal resistance, which causes their voltage to drop when they are under load. They also have a limited capacity, meaning that eventually they will drain and need to be replaced or recharged. How does a battery's voltage change over time as it is used in a common household device? When does the battery "die" and cause the device to stop functioning — does the voltage drop all the way to zero, or is it before that?

To investigate this problem, you can use a multimeter, a tool that can measure both electrical voltage and current (and other things, like resistance). If you need help learning how to use a multimeter, check out the Science Buddies Multimeter Tutorial. Pick a battery-operated household device that you can leave on continuously to drain the battery (for example, a toy with a spinning motor and an ON/OFF switch would work well, a TV remote would not work well since the batteries last for a very long time). Put fresh batteries in the device, turn it on, and then use a multimeter to measure the batteries' voltage in regular intervals (see notes below). Record your data, and then make a graph with voltage on the y-axis and time on the x-axis. How does the batteries' voltage change over time? At what voltage does the device stop functioning? Can you do the same test for other devices or types of batteries?

Here are some additional notes and suggestions on taking your measurements:

To get you started on your background research about batteries, see the Bibliography. For a more advanced project, look up the data sheet and "discharge curves" for a specific type of battery. Devise an experiment to take measurements and create your own discharge curve, then compare it to the official data from the manufacturer.


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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Finio, Ben. "Batteries: The Shocking Truth." Science Buddies, 20 Nov. 2020, https://www.sciencebuddies.org/science-fair-projects/project-ideas/Energy_p011/energy-power/batteries-the-shocking-truth. Accessed 26 Sep. 2023.

APA Style

Finio, B. (2020, November 20). Batteries: The Shocking Truth. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/Energy_p011/energy-power/batteries-the-shocking-truth

Last edit date: 2020-11-20
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