A USB Power Bank is an external battery that can be used to charge electronic devices. It is a portable device, usually small enough to fit in a pocket or purse, that contains a rechargeable lithium-ion battery and a USB port. The USB port allows you to connect your device, such as your smartphone or tablet, and charge it while on the go. The Levo PA71 is one of the most popular models of USB Power Banks available today. It has an impressive 7100 mAh capacity and can charge up to four devices at once with its dual USB ports. This makes it great for long trips or days when you need extra power for multiple devices.