How to Recover Data for an iPhone With a Dead Batteryby Jim Campbell
The iPhone ships with a USB data cable that you can use to recover data from a backup, even if the battery in your mobile phone is dead. The battery recharges while the iPhone is connected to a computer via the USB cable, and you can recover data on your phone at the same time. Use iTunes to back up and recover your contacts, apps and other information if your data becomes corrupt because of a software glitch or the iPhone crashes.
Connect the iPhone with the dead battery to your computer using the USB cable. ITunes detects the connected device and opens automatically.
Click the "iPhone" icon in the left panel. Several options for the iPhone will display. Click the "Summary" tab and then from within that tab click the "Restore" button. The recovery process begins.
Click "Backup" if you want to create an additional backup of the current settings before you restore your data. You can skip this step by clicking "Don't Back Up."
Click "Restore" to recover data from a previous backup. This process takes several minutes and iTunes will display a success message when your data is restored. Click "OK" to close the recovery window.