In iOS 8 you have the possibility to minimize an app till you work in another one and when you finish, return to the minimized again. This is meant to be a cool multitasking feature to facilitate your work, however unconscious this feature becomes a trap that actively drains your battery and eats operating memory. It refreshes for new information into background that when the app re-opens you don’t need to wait till it refreshes. If you don’t need the app just quit it.
If you don’t use this feature turn it off. You will still be able to minimize apps, but they wouldn’t Refresh in the Background.
Turn off Background Refreshing feature
Head to Settings app > General > Background App Refresh
Here you’ll find a list of apps installed on your computer.
To turn off the feature for all the apps, tap on the toggle switch next to Background App Refresh.
To turn off the feature for specific apps, tap on the toggle switch next to the specific App.