How Do Batteries Work and Run Out?

From the Lecture Series: Understanding the Misconceptions of Science

By Don Lincoln, Ph.D., University of Notre Dame

Batteries are simple yet useful inventions. A common belief about how batteries work is that they ‘store’ a specific amount of electricity inside, which is fully consumed after several times of use. Thus, the battery dies. As logical as it may seem, it is not even close to the reality of batteries and their energy-production process.

a selection of batteries
Despite their simplicity, batteries are often misunderstood. (Image: silabob/Shutterstock)

Batteries have been around for so long that they are overlooked. Many people think this is how batteries work. They are small pots that have a capacity for storing electricity. When one is put in a machine or any kind of circuit, the electricity comes out of the positive and negative ends, and the machine feeds on that energy. After a while, the stored electricity is fully consumed, and the battery dies. All these assumptions are far from the scientific reality of how batteries work.

Faraday Cage and the First Misconception

The Faraday cage is a concept in physics that explains what happens to an electric charge in a metal shape. If a metal shape, here the cube around the battery, receives an electric charge, the charge tends to move to the outmost layers of the shape. Hence, if there were any electricity stored in a battery, it would move to the outer surface. This would cause an electric current every time a person touches a battery, which can range from a small spark to a fatal bolt depending on the battery.

This is a transcript from the video series Understanding the Misconceptions of Science. Watch it now, on Wondrium.

An electric DC battery at an electrical station.
Not even the biggest batteries store electricity inside them. (Image: Dzmitrock/Shutterstock)

However, all types of batteries, even the huge ones in the auto industry, can be held with no electric shock whatsoever. Consequently, the first belief that batteries store electricity is impossible.

Learn more about How Relativity Is Misunderstood.

The Positive and Negative Ends

There are two types of electric charge: negative and positive. The positive side refers to the nuclei of atoms that get their charge from the protons and negative represents the electrons. An equal number of protons and electrons will result in a neural net charge. A battery holds the same number of protons and electrons. Thus, it is completely neutral. How does it produce energy then?

The Chemical Reactions

The chemistry inside a battery determines how it works. In a battery, electrons are pushed to the negative side and away from the positive side. However, the positive nuclei cannot move as easily, and, as a result, opposite charges accumulate on the two sides.

Selective focus an auto mechanic uses a multimeter voltmeter to check the voltage level in a car battery.
Chemical reactions make the battery produce the necessary energy. (Image: CC7/Shutterstock)

When a battery is put in a circuit, the charge moves through that circuit. This causes a chemical reaction inside the battery, which ultimately creates an electrical current.

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The Electrical Current: What Moves Around?

Theoretically, the positive side of the battery can be thought of as the place where positive charges leave the battery and rush to the negative side. Electrical current is defined to be just the motion of positive charges, and its direction is just the direction of the motion of positive charges. Like the other battery-beliefs, this is scientifically wrong.

As mentioned above, the nuclei are heavy and do not move around easily. Even the chemical reactions have to push the electrons to the other side to make the protons’ side positive. Thus, the electrons move. They go from the negative side of the battery and then zoom around the circuit over to the positive side. Thus, the reality is exactly opposite to what most people think.

How a Battery Dies?

Eventually, enough chemical reaction occurs in the battery that there is no remaining tendency to separate positive and negative charges. When the tendency dies, so does the battery.

Batteries work in a totally different way than most people expect them. They work as the result of chemical reactions and the tendency of the battery to become neutral and make the balance between positive and negative sides.

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Common Questions about How Batteries Work

Q: How do batteries store energy?

Batteries do not store energy by storing electricity. The number of nuclei in the positive and electrons in the negative ends should be enough to make the necessary chemical reactions occur. The production of electricity happens only when the battery is a part of a circuit, and that is how batteries work.

Q: How do batteries work, simply explained?

Many people think storing a specific amount of electricity is how batteries work. But that is not true. The simple explanation of how batteries work is that the chemical reactions in the battery make electrons move along the whole circuit, as the protons try to make a balance and drag the negative forces, i.e., electrons, toward themselves. Thus, an electrical current is created.

Q: How does the chemical reaction in a battery work?

The chemical reactions are the main element of how batteries work, besides an equal number of protons and electrons in the positive and negative ends. The chemical reactions make the battery separate the charges. However, the intensity of the process diminishes until there is no tendency of separating left. In fact, they make the electrons move in the desired way.

Q: What happens when a battery dies?

The negative and positive ends of batteries determine how they work. When a battery is connected to a circuit, the charge moves through the circuit, and a chemical reaction occurs inside that separate the charges. The strength of this reaction diminishes over time and the battery eventually dies.

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