If you keep a charger pluged in at all times this is a drain on the battery and can cause it to fail over time. Had the same thing happen to me on my '07 MKZ. My girlfriend was driving the car mostly and she kept her phone charger pluged in and it eventually ruined the battery. Lucky for me it was still under warrently like yours
Ok lets settle this once and for all.
Lets see your Hyundai do this.
http://www.facebook.com/l.php?u=http%3A%2F%2Fwww.youtube.com%2Fwatch_popup%3Fv%3D4TshFWSsrn8%26vq%3Dmedium%23t%3D35&h=0b072
My link