How to Charge an iPhone From a USB Portby C. Taylor
Plugging Apple's USB power adapter into a wall outlet offers the quickest charge time for your iPhone, but this method isn't always the most convenient. As an alternative, your computer's USB port will charge the iPhone, but you need to be careful which USB port you use. Keyboard USB ports do not offer sufficient power to charge your iPhone, and USB hubs may have available power divided among multiple devices. For the speediest charge time, use a primary USB port and disconnect all other USB devices.
Wake up the computer if it's currently in sleep mode. Attempting to charge the iPhone from a computer in sleep or standby mode could drain the iPhone's battery.
Unplug other USB devices from your computer to obtain the quickest charge time.
Attach the iPhone's USB cable from the bottom dock connector to a USB port on the computer itself. Do not use a keyboard USB port or a USB hub.
- Using your iPhone while it is charging lengthens the charge time. For the quickest charge time, leave the iPhone in sleep mode, close iTunes and refrain from attaching other USB devices to your computer.