I was about to fly my P3S, so I checked the battery inside. It was fully charged; 100%. Then I went outside and turned the controller and Phantom on, and all of a sudden it said that battery was 56%, and after running everything up and flying for a minute, it was down to 51%. I flew for about 14 minutes, but it mostly stayed at 51% for half the flight, then 50% until the end. The outside air temperature is 42 degrees Fahrenheit. This is the first time I've had this happen, but also one of the coldest flights it has done so far. Any ideas?