Starting, lighting, and ignition (SLI) batteries are a type of lead-acid battery primarily used in vehicles. They provide the necessary power to start the engine, as well as to operate electrical systems like lights and radios when the engine is off. SLI batteries are designed for short bursts of high current, making them ideal for starting engines. These batteries typically consist of lead dioxide and sponge lead plates submerged in an electrolyte solution of sulfuric acid. When the battery is charged, a chemical reaction occurs, allowing it to store energy. When needed, this energy is released quickly to start the engine and power electrical components.