Healthy Battery Charging
Healthy Battery Charging alerts you when to plug or unplug your phone from the charger to improve battery life. The app itself is optimized for low battery consumption, running in the background and checking the battery level every 15 minutes. The exact timing of these checks depends on the Android operating system, which may schedule them alongside other tasks or delay them in sleep mode. As a result, the battery level may slightly exceed the high threshold while charging or drop slightly below the low threshold while discharging before you receive a notification.
For those who want to know more about the technical details of Li-ion batteries:
https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
Healthy Battery Charging | F-Droid - Free and Open Source Android App Repository
Prolong the life of your battery by keeping it charged between 40% and 80%

