movie (mp4): 49min/16% => 306 min total
photo slides: 45min/11% => 409 min total
music (mp3 w/ extenal earpiece): 31min/2% battery => 1550 min total (??)
youtube HQ (4G): 20min/8% => 250 min total
GPS/Gmap navigation: 23min/9% => 255 min total
use auto brightness