How can I tell when the Moment is completely done charging? I use a wall charger. When I plug it in. The screen lights up. Phone charging. Seconds later. The screen goes blank.. I have to manually hit the volume key or end key to see the charge complete notification on the screen. I charge it for about 4 hours. Isnt it suppose to light up on its own with the charge complete? Do I have a defective MOMENT? Thanks