A USB power bank is a portable charger that stores energy in a rechargeable battery and can be used to charge your electronic devices. It is an external battery pack that allows you to charge your devices on the go, without having to be connected to an electrical outlet. The most common type of USB power bank is the Levo PA71, which has a capacity of 7100 mAh and can charge up to three devices at once. It also comes with two USB ports for charging and one micro-USB port for charging the power bank itself. By understanding how these portable chargers work, you can make sure that you are always able to keep your devices charged when you’re away from home or office.