Just to throw this in...it was noted somewhere on this forum that the extenders will lose power even when not turned on (I don't know how, why or if it's true). I just make a habit of plugging it into an extra cell phone charger the night before I plan to fly. That said, when I was flying with 2 batteries in the winter and in bitter cold conditions, I never had a time when the extender would change from green to orange (low battery) while operating it. however, anytime I plug it in to the charger, even if I haven't used it, it will always give an orange light for a period of time before it turns green. And don't watch for it to turn green while you're waiting--it makes it take longer!