Power tool batteries are rechargeable energy sources designed to power various tools, such as drills, saws, and sanders. They come in different types, including lithium-ion and nickel-cadmium, each with unique characteristics. Lithium-ion batteries are popular for their lightweight design and longer run time, while nickel-cadmium batteries are known for their durability and ability to perform in extreme temperatures. These batteries are typically rated by voltage and amp-hour capacity, which indicate their power output and how long they can run before needing a recharge. Proper care, such as avoiding complete discharge and storing them in a cool place, can extend the lifespan of power tool batteries.