21700 batteries are a type of rechargeable lithium-ion battery that are becoming increasingly popular due to their high energy density and long battery life. They are larger than the commonly used 18650 battery, measuring approximately 21mm in diameter and 70mm in length. These batteries are commonly used in electric vehicles, high-powered flashlights, cordless power tools, and other demanding applications that require high performance and long-lasting battery life. A single 21700 battery can provide a voltage of 3.7 volts and have a capacity of up to 5000mAh, making it a powerful and reliable source of energy. Due to its relatively large size, it offers more capacity while still being compact enough to be used in portable devices effectively. These batteries also have a longer lifespan, making them more environmentally friendly and cost-effective over time.