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. This design allows for efficient energy storage and delivery, making them reliable for starting engines and providing power during outages. These batteries are known for their durability and cost-effectiveness, but they are heavier and have a shorter lifespan compared to newer technologies like lithium-ion batteries. Despite this, their ability to deliver high surge currents makes them ideal for applications such as automobiles and uninterruptible power supplies.