An external charger, also known as a power bank, is a portable device used to recharge electronic gadgets like smartphones, tablets, and laptops. It stores electrical energy in its internal battery and can be connected to devices via USB or other charging ports. This allows users to charge their devices on the go, making it convenient for travel or outdoor activities. External chargers come in various sizes and capacities, measured in milliampere-hours (mAh). Higher capacity chargers can recharge devices multiple times before needing to be recharged themselves. Many modern external chargers also feature fast charging technology and multiple output ports for charging several devices simultaneously.