How to Recharge Your iPhone
You must recharge your iPhone from time to time. If your iPhone acts up in any way, the first thing you should try is to give its battery a full recharge.
Plug the iPhone’s dock connector-to-USB cable into one of the USB ports on your computer, rather than into a USB port on your keyboard, monitor, or USB hub. The USB ports on your computer supply more power than the other ports.
You can use the included USB power adapter to recharge your iPhone from an AC outlet rather than from a computer.