We did a bit of ‘science’ this weekend. I needed to test the GoPro batteries and decided to document some of the process for you guys. I’m including a short video and some photos to help with the conversation.
All batteries deliver power through chemical reactions that release electrons. When the temperature drops, the chemical reactions happen more slowly and the battery cannot produce the same current that it can at room temperature.
The batteries will be exposed to ground level temps of 40-70 degrees depending on the day/time of launch and then as we climb higher and and higher into near-space, you can calculate an average of 3 degrees lost for every 1000 feet of altitude gained. At some point this linear graph breaks down and we we approach a near vacuum and temperatures I can’t recreate in my home; anywhere from -30F to -60F.
For this test, I charged two GoPros overnight, fully topping them off, and then exposed them to a constant 0F of a standard home freezer. It doesn’t move the cameras through the same temperature profile but it serves our purpose and gives us a baseline for mission length and what we should expect to get photos and videos on the flight.
Here’s the recap video:
In addition to video, I wanted to test the battery life of GoPro cameras in time-lapse photo mode. When the camera recognized the 64GB micro-SD card, the menus showed me that it would hold ~23,350 photos at 10 Megapixel (~3mb/photo). I assumed that we would get more battery life than in video mode because there is less draw. You might think that it would get 30 or 60 times the battery life because it’s only one frame per second vs 60/sec video but it doesn’t really work that way. The camera is still ‘on’, and timing, and storing, and metering, etc etc.
It turns out we get a pretty impressive battery life in ‘Camera’ mode: I started the test at 2:29pm and the last photo was written to the card at 6:54pm. This means we got 4 hours and 25 minutes of photos at one photo per second (compared to 3:11 for video)
You SHOULD see the last photo was taken at 4:25 on the alarm clock in the freezer but it was a blinking clock that started counting up from 12:00. It was very interesting to watch the photos come in and out of phase at once per second; for many photos the numbers were ‘on’ and then for many frames the numbers were ‘off’. Trust me, it lasted 4:25 and I can tell by the time stamp.