If it helps this discussion at all. Many are saying this is a result of installing battery apps and such. I can say that I just got this phone about 1.5 weeks ago. I never installed any apps that can influence anything about the batteries. I did not do anything different or installed anything today. But as of a couple of hours ago it started doing that fully-charged beeping thing every 5 minutes or so as long as it is plugged in. Device notifications are set to silent. System sounds volume are set to minimum.
So that shows:
- it's got nothing to do with battery apps.
- it's got nothing to do with device notification or system sounds.
Edit: Since some people on various different forums are saying that it maybe the charger issue, I decided to tried using a different cable. (I have an external battery that comes with its own cable). So I used Samsung's charger, but connected it to the phone using the cable used by the external battery, and it had been quiet since.