If you want to display the battery charge state as percentage in the status bar under Android Marshmallow, then you have to enable a few settings and options.
Because these battery indicator was integrated somewhat hidden in Android Marshmallow. Below we briefly explain to you how you can display on a Smartphone with Android Marshmallow the battery indicator in percent:
1. First activate the so-called Android UI System Tuner. For instructions how to do this please read the following article
2. Now open the menu under Android marshmallow and then the settings
3. Now a menu icon with "System Tuner UI" appears. Tap on this to get to the next submenu.
4. Now you can find the option to display the battery charge level as a percentage on the notification bar here. Enable this option by using the controller.
Super you have just enabled the battery indicator as a percentage in the status bar on your smartphone with Android marshmallow. Thus, you can now watch exactly how the battery level changes and when you will have to charge.