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How battery chargers work

If you've read our main article on batteries, you'll know all about these portable power plants. An example of what scientists refer to as electrochemistry, they use the power of chemistry to release stored electricity very gradually.

What happens inside a typical battery—like the one in a flashlight? When you click the power switch, you're giving the green light to chemical reactions inside the battery. As the current starts flowing, the cells (power-generating compartments) inside the battery begin to transform themselves in startling but entirely invisible ways. The chemicals from which their components are made begin to rearrange themselves. Inside each cell, chemical reactions take place involving the two electrical terminals (or electrodes) and a chemical known as the electrolyte that separate them. These chemical reactions cause electrons (the tiny particles inside atoms that carry electricity) to pump around the circuit the battery is connected to, providing power to the flashlight. But the cells inside a battery contain only limited supplies of chemicals so the reactions cannot continue indefinitely. Once the chemicals are depleted, the reactions stop, the electrons cease flowing through the outer circuit, the battery is effectively flat—and your lamp goes out.