Power banks have become an essential mobile accessory . There are some features that a power bank must possess . First is that your power bank’s capacity should be of at least 10, 000 mAh, so that it can charge your phone battery three or more times . Second is that its size should be handy so that you can use it while travelling in train, bus, etc . Third is that it should have at least two charging ports i.e. it can simultaneously charge two devices in case of emergency . another important feature is that it should support fast charging, so that it can take less time for charging up . Find a power bank having similar features as discussed above and read its customer reviews before buying it . In this way you will never be disappointed by your decision of buying a particular power bank .