Does the Google Authenticator app negatively impact a fully charged device I have the Google Authenticator installed on my phone. I notice the codes are generated constantly. It appears the app is running constantly in the background. 

Does this app has a major impact on a fully charged android device?
The app is not running in the background.  When you start it, it generates codes based on an algorithm tied to your original configuration.

It for sure will not impact your battery, and is not running in the background (the time based codes it creates, are constantly changing though - every 60 seconds - or however long).

But the app is only using resources when it is running, and servicing out the codes to you.