I purchased a brand new iPhone 5s a little over a week ago. I noticed right away that it would never charge to 100% so I let the battery drain all the way down until the phone shut off, then I charged it all the way back up. After that it would charge to 100% and everything seemed ok. Now it charges to 100% but with the charger still connected, it starts to drop. When I woke up this morning it was down to 96% and the charger was still connected. Should I take it back to Apple or is this normal?