Lead-acid batteries are a type of rechargeable battery commonly used in vehicles and backup power systems. They consist of lead dioxide and sponge lead plates submerged in a sulfuric acid electrolyte. When the battery discharges, a chemical reaction occurs, producing electricity. These batteries are known for their reliability and ability to deliver high surge currents, making them ideal for starting engines. Despite their advantages, lead-acid batteries have some limitations. They are relatively heavy and have a lower energy density compared to newer battery technologies like lithium-ion. Additionally, they require regular maintenance and can be less efficient in deep discharge applications, which can shorten their lifespan.