Gaston Planté invented the first rechargeable battery, the lead-acid cell. Unlike the voltaic pile, which was discarded once the chemicals were spent, Planté’s battery could be recharged by passing a reverse current through it. This was the first practical way to store large amounts of electricity. Today, despite 150 years of progress, lead-acid batteries are still used in almost every car on the planet to start the engine. They were the essential first step toward our modern world of portable power and renewable energy storage.