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How does a lead-acid battery generate electricity?

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Study how a series of gears in a waterwheel translates a stream's energy to a millstone — energy conversion Before the Industrial Revolution, power came from three main sources: humans, draft animals, and water.
The ingenuity people used in harnessing waterpower can be seen in this medieval-style mill. The waterwheel is turned by a stream and is connected to a shaft that leads into the building. At the other end of the shaft is a gear. The connection of a series of gears translates the power from the stream to a shaft that drives a millstone, which grinds flour from grain.
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A lead-acid battery generates electricity through electrochemical reactions that occur within its voltaic cells. Each cell contains a positive electrode coated with lead dioxide and a negative electrode made of spongy lead, both submerged in an electrolyte of sulfuric acid and water.12

During discharge, the following processes occur:
* Positive Electrode: Lead dioxide reacts with the sulfuric acid to produce lead sulfate and water.12
* Negative Electrode: Lead combines with sulfate ions from the acid to form lead sulfate, releasing electrons in the process.12

This flow of electrons from the negative to the positive electrode through an external circuit provides electric current. As these reactions proceed, the sulfuric acid is consumed and water is formed, which dilutes the electrolyte and lowers its specific gravity. Because these chemical transformations are reversible, the battery can be recharged by applying an external power source to drive the reactions in the opposite direction.12