Some background apps crash, go rogue and drain your battery completely. So, while it may seem that your iPhone is charging slowly, the background apps are rapidly depleting the battery. In this instance, you can force all open apps to close or switch off your iPhone while it is charging.

1. Quickly press the Home button twice. This brings up the Apps viewer screen, which displays a list of recently used apps. These apps are in the background and in standby mode.
2. To close the app preview, swipe up.
3. Repeat for the remaining background apps.