(1)DO not used for charging,it is used for offering more usb ports to transfer file.(2) The power supply can solve the problem of insufficient power supply, if you need work with a hard disk , then you should choose the with power supply , and please note ,please don;t use more than 2 hard disk at the same time(3) The power supply can improve the usb transmiion speed1. 100% brand new and high quality2.Hot plug & play USB device3. Fully compatible with USB specification version 3.04.With blue LED for power5. ON/OFF switches activate or deactivate individual ports6.Designed with 7-port,this compact USB3.0 high-speed hub is small enough for travel,and cable enough to meet your connectivity needs7.Thespecification of the power supply is , 5V 2A. Features:7-port USB 3.0 hub, ultra-high speed transmiion, generous design, reasonable interface layout, no interferenceFeatures Each USB port LED is designed to control each USB deviceSupport overload voltage and instantaneous current protection, effectively protect the connected equipment and HUB itselfConforms to USB 3.0 specification, supports high-speed 5Gbps bandwidth transmiion, and backward compatible with USB2.0 / USB1.1Free driver support for Windows XP / Vista / 7/8 and MAC with USB support