A USB power bank is a portable charger that allows you to charge your devices on the go. It is an external battery pack that can be used to charge your mobile phones, tablets, and other USB-powered devices. The most popular USB power banks are the Levo PA71, which has a capacity of 7100mAh. It has two USB ports and one micro-USB port for charging multiple devices at once. This power bank also comes with an LED indicator so you can easily monitor its charge level. With this device, you can make sure that your device never runs out of battery when you are away from home or office.