With this app you can easily change the setting to show the battery percentage in Android 4.4.* (KitKat) 5.* (Lollipop) 6.0.* (Marshmallow) 7.* (Nougat) and 8.0 (Oreo).


KitKat: Reboot the device to apply the setting. The percentage text is always white only visible when the battery empty enough.
Lollipop: Reboot the device to apply the setting. The percentage text is always visible because the text color changes depending on the level of the charge of the battery.
Marshmallow / Nougat: The setting will be applied immediately. Rebooting the device is unnecessary. The percentage text is always visible because the text color changes depending on the level of the charge of the battery.
Oreo: The setting will be applied immediately. The percentage is shown next to the battery. The setting will be kept after the app is uninstalled.

Works without root.

Uninstalling the app does not hide the battery percentage on the icon before uninstall turn off the setting in the app.

This app may not work if the system ui on your phone has modification by the manufacturer (e.g. touchwiz sense etc) or using custom rom which has built in option for battery icon modification