The Fueltank Duo charger is a heavy duty charging device that will charge up to 3,000 different mobile devices across all major brands. It has two output ports so it can charge two devices at once. It contains a rechargeable lithium ion battery that has 7 times the capacity of most mobile devices. Each cable connected to the Duo uses a common interface to the main unit with a device specific connector on the other end. Therefore you can easily recharge an iPhone and, say, a Sprint phone at the same time if you have the appropriate device adapters.