is another screen app, this one is older but lets you lower the brightness level to barely viewable. great for wanting to see your phone in a dark club or bar and you dont want your phone to attract alot of attention.
protip: when you are installing apps while this is running it wont let you because that's androids way to prevent malicious apps from tricking you into installing malware or something like that. so if you have trouble installing apps, try turning off this app first.
Other things you can do to save power:
turn down the brightness of your screen
turn off gps, nfc, blutetooh, wifi, lte, ect, when not in use. (i have noticed that wifi uses less power than the cellular radio)
try under volting and under clocking your CPU (advance users only)
use a task manger app to disable apps that you may not use (advance users only) this can also decrease your bootup time.
Greenify man, just because.https://play.google.com/store/apps/details?id=com.oasisfeng.greenify Mostly, battery life comes down to just turning off the stuff you are not using.
For the screen darkening one I use Lux Autobrightness, much better than the system brightness control. You can set brightness curves based on how much light is in the room and like F.Lux you can have it yellow the screen automagically at certain times of day. You can also darken the screen for night time use and the premium version has a stargazing mode that turns the screen red to not break you night vision.
I am rooted dont have that problem. I do have to hit the icon every so often to use the program. You have to set it up to hibernate stuff, then use it. I use mine a tablet thats has hundreds of apps on it. Maybe the app is not that good if using it only for a few things?
I used Greenify on a previous Android phone I used to hibernate the Google Play services. Only went down 3% after a day of not really touching the phone only to check gmail for youtube subscriptions.