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How does a lead-acid car battery produce electricity?

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Cross-section diagram of an alkaline-manganese dioxide battery showing labeled internal components, including the steel-plated covers, cathode, anode gel, current collector, separator, steel can, and brass rivet. — battery Cutaway view of an alkaline–manganese dioxide power cell.

A lead-acid car battery produces electricity through chemical reactions that occur within its voltaic cells. Each cell contains a negative electrode made of spongy lead and a positive electrode made of lead dioxide, both submerged in an electrolyte solution of sulfuric acid and water.12

During discharge, these materials react to form lead sulfate and water. Specifically, the lead at the negative electrode is oxidized, releasing electrons, while the lead dioxide at the positive electrode is reduced, consuming electrons. This separation of oxidation and reduction processes creates a potential difference (voltage) between the electrodes, driving an electric current through an external circuit.12

A standard 12-volt battery consists of six of these cells connected in series, with each cell providing approximately two volts. Because these chemical transformations are reversible, the battery can be recharged by an external power source, which reverses the reactions and restores the original chemical composition of the electrodes.13