Sometimes state of charge estimation algorithms have problems with current battery level estimation To have some reference on available charge level user can take into account current battery voltage state.
Glee Fabric is the creator of Battery Voltage Notifier that is listed among the Tools category. The latest update of the app was launched on Oct 2, 2018 and this application was downloaded by over 10K users. Google Play shows that Battery Voltage Notifier is rated 4.5 by its users.
This application contains advertisements. Download the free installer of Battery Voltage Notifier 1.9 and take a look at users' reviews on Droid Informer. The app runs on Android devices 4.1 and higher. This download is totally safe.