18650 button top unprotected batteries are a type of rechargeable lithium-ion battery that features a protruding button top, which makes it easier to install and remove from certain devices. As the name suggests, these batteries are not protected, which means they lack safety features that prevent overcharging, over-discharging, or short circuits. Therefore, they require careful handling and should only be used in devices that have built-in safety measures or with additional protection circuitry. These batteries are commonly used in high-drain devices such as flashlights and electronic toys due to their high capacity, voltage, and discharge rate. It's important to note that these batteries must be charged with a compatible lithium-ion battery charger to ensure safety and longevity.