Ever noticed how your iPhone battery drains so much quicker while outside in the sun? Is it because you have auto brightness turned on? Outside on a sunny day the light is so bright that the phone’s auto brightness circuit will turn the screen backlight up to number 11 however you can actually see the phone’s screen pretty well in full sunlight, even when the brightness is turned all the way down. So if you need a few more hours on the sun lounger try turning off auto brightness and dim the screen fully to save quite a lot of battery power.