I recently updated my galaxy watch 2. Since the update my watch as been dieing very quickly. Last night I went to bed with 50% and woke to it being dead. Why is this happening and how to I fix it?
Check Background Apps and Stop Them.
In my case, the stock Gallery App was stuck running and sucking down all of the battery life, even AFTER several shut downs & reboots!
Open Galaxy Wearable App
Press the top summary where it shows the watch face, battery, etc.
Look at the Apps near the bottom under "Battery Usage Since Last Charge"
If you find a high-usage app, Press it, then Press "Force Stop" (bottom-right).