Battery Ace is a nice customizable widget to keep track in detail of your battery level percentage.

Widget Features:
- several styles to chose from.
- 3 modes: level, time left and temperature.
- re-sizable widget with high quality graphics
- numerical battery percent in widget
- option to show charge / discharge time left (estimated)

App Features:
- discharge prediction (estimates how long the battery lasts)
- charge prediction (estimates how long until full charge)
- graphical history of battery usage
- Battery level warnings
- battery details (Temperature, Voltage, Health, Status, etc.)
- widget designer to configure every detail of the widget
- Customize widget levels limit and colors.
- Notification Bar with icon showing a readable percentage.
- Support Dark Mode
- Ads free

Notes:
- Task Manager, Task Killer or other power saving features (often built in the system) may affect this app. Please don't use them or try to create an exception for this app if it does not work as expected.
- The App is very light and optimized and should NOT drain you battery
- Due to the limitation of the Android platform, home screen widgets will NOT work if the app is moved to the SD card.