Charge Level Control Would there be any application or method of controlling the charge level and limiting it for example to start charging at 20% and stop charging at 80% ?
You could use Tasker to make a beep or push a notification when battery level is ouside your safety boundaries, so you can take an action by yourself (ie. un/plug the charger). 

Go to developer website, where Tasker Userguide can help you to set that task, taking as context the State of your device.

The following image shows an example of configuring Tasker to take an action depending on battery state: