I brought along my new GoPro Hero Black 7, my Mavic Air with the iPad, and my iPhone 7.
In the morning I took my GoPro with me to the slopes. Fully charged batteries. I put the GoPro in my pocket of the trousers. The first hour, worked pretty good, no problems with the GoPro. On the second run, I started the GoPro recording, and when I arrived at the bottom, the GoPro was off. When I restarted the GoPro, it showed 3% battery life.
Replacing the battery with my second one, solved the problem. I but the “empty” battery back into my inner jacket pocket, which was a lot warmer. And sure, when I put the battery back into the GoPro, it showed 56%. Clearly the battery froze.
Later in the day, at the Honigland, where my girls learned skiing, I took out my Mavic Air.
All fine, battery full on the Drone and iPad. I flew to the “Haupti-Chopf” and back, no issues. Then I about 8-10min into the flight, the iPad turned off! This was a scary moment, as I was not able to control the drone. I pressed the “return to home” button on the controller which brought the drone back to me. In the meantime I exchanged the iPad with my iPhone, started the “DJI Go 4” app, and landed the drone safely in my hand.
Bottom line, neither the GoPro nor the iPad (and the iPhone) like the cold. Interestingly, I never had issues with my Nikon D850 (and D6xx) battery life in cold weather this way.
So either try to keep the battery warm, or have enough spare warm battery close to you.