My note 9 is now doing this even if it's not on the charger. Alerting me repeatedly. It's a new to me phone, and the annoyance has me seriously considering sending it back if im still in the return window.
I love the phone. And the spen certainly comes in handy on occasion. But I'd have no issue going back to my s9 if need be.
This is also happening on my BRAND NEW GALAXY S8! I just purchased it from Sam's Club and I have been issued a return shipping label. I really like this phone, but I WILL NO HESITATE to return it for a full refund! This better not be some "push an update to make the phone obsolete".
August 25, 2019
IMO, The "Weak Charging Detected" notification is obviously an error in one of Samsung's pre-installed maintenance apps that updated over the Summer.
To stop this false notification, I opened the "Samsung Members" application on my S-9, navigated to "settings", then turned off the switch for "Diagnostic Notifications".
Restarted the phone, and the annoying "Weak Charging" notifications have not reappeard. I hope this EASY "fix" is as effective for everyone else as it was for me. Good luck!
-Allen in Chicagoland