1. Use your iPhone until it shuts off automatically. If it is near 0% battery life and you want to drain it faster, turn on the flashlight, turn up screen brightness all the way and play a video, preferably streaming from the Internet.
2. Let your iPhone sit overnight to drain the battery further.
3. Plug your iPhone in and wait for it to power up. Make sure to use the charger supplied by Apple or one that runs at the same wattage and amperage.
4. Hold down the sleep/wake button and swipe “slide to power off”.
5. Let your iPhone charge for at least 5 hours. The charge progress indicator is not displayed while your iPhone is turned off.
6. With the charging cable still connected, press the sleep/wake button for about a second to start up your iPhone.
7. When the iPhone has booted up, hold down the sleep/wake and home buttons until you see the Apple logo.
8. When your iPhone is back online, remove the charging cable.