How to stop power intake when completely charged? Is it possible a process should run in the background of Android OS, 
 and the only task of that process is to stop the power intake to the device when the battery is completely charged?
Have you tried Battery Charge Limit 0.1? I haven't really tried it myself due to incompatibility with my android version. 

It requires root and android versions 4.4+

you can find it here: Battery Charge Limit 0.1 4.4+