Most of our power bank comes with a simple USB cable that is only used to charge the power bank itself. Plug the USB side into your phone's wall charger or into a USB port of your computer and the Micro USB side into the power bank to begin charging. The output port is used to charge your phone or mobile device. A Mobile has turned into a need today and we can scarcely work without one within reach. from messages to PPts to Bankings, Business Operations, Office Work, Gossips we as a whole are in a need of a cell phone. So is the need to keep our gadgets Charged and prepared to go.