Have you tried developer mode?
To show developer mode on samsung galaxy:
1. Settings, the more tab, finally about phone
2. Click "build number" repeatedly. Then a little message should pop up and day that is has unlocked
3. Click back once and you should see "developer mode" option
4. All the way at the bottom there's an option where it you can restrict how many apps run at all times. Improving Your Battery.
have you dimmed yours light on your phone?