I know this has been reported already, and Garmin supposedly has already fixed this, but the issue persists for me. Here are just some data points that I have observed during today's night race.
Satellite mode: All + Multi-band
Race duration: just under 5 hours
Estimated activity battery life when starting the trail run activity before the race: 15 hours
Estimated activity battery life when starting another activity right after finishing the race: 7 hours
Backlight brightness: 40% (however this should already be factored into the battery life estimate)
Wrist gesture: always
Backlight timeout: 8 seconds
So, basically, the watch used 8 hours worth of battery life in 5 hours. That is 60% higher battery usage than estimated. I understand that the wrist gesture may result in some additional backlight use. I looked at the watch perhaps about 1-3 times per mile, so perhaps 100 times at most in 5 hours. Plus there were 29 autolaps. So, perhaps, if everything worked correctly that would result in about 1000 seconds of backlight time - that is about 16-17 minutes, and some of that should already be baked into the battery estimate. But missing the estimate by 60% seems overly excessive.
My observation is that the watch display was lit perhaps half of the time. The wrist gesture detection isn't really working. It is way too sensitive. This is an important feature considering poor sapphire display readability, but it is doesn't work, and that leads to excessive battery use.
