Apple Watch Series 4, 5.2.1, iOS 12.4
Usually I have no battery life issues. I often wake up in the morning at full charge and go out for an hour-long run or trip, and come home with ~ 90% left. At the end of a full day, I'm often around 50%. I don't think there's anything wrong with my battery.
However, sometimes (maybe every three months, it has happened 4-5 times now), I will go for a morning workout and within 30 minutes receive a 10% low battery warning, followed by the clock dying. It seems to be completely random, other than that it always happens during an outdoor exercise. I can't figure out what is causing it.
Other info: I don't usually take my phone. I don't listen to music. The area I usually find has limited to-no cell phone service. I use the original training app. I have not seen this problem with indoor workouts (but I do less of them, so given the periodic nature of this problem, it might just be coincidence).
Any ideas welcome …