Absolutely no reason it could go dead on 3 hours of the usage you explained. A petty as it may sound... Did you go over everything that was mentioned previously in this thread? Did you try a reset and recharge?
Posted via the Android Central App using the Note 4
I've had my Gear S along with a note 4 November of last year. I was always able to get two full days and one night out of the battery on the S Gear, & I had excellent battery life on my Note.
In the last week or so, though, my Gear S has been draining down to zero within four hours. The phone was also losing battery very quickly, draining to 40% in less than 6 hours. I went to the T Mobile store, and they told me that it was my battery, and they would send me out a new watch. I was surprised, because it had been working perfectly, but I figured that batteries do die, although 10 months did seem way too soon.
I really didn't want a refurbished watch that have been somebody else's problem, because who knows if they had ever really even found what was wrong with it, & it just looked good so they sent it back out again.
I looked at the Battery Manager on the phone to see what was eating my battery life, & I discovered that it was two Gear programs that had never popped up on the Battery Manager radar before. So I turned to my trusty friend Google, and discovered that the culprit was the gear manager program on the phone. It had somehow updated itself incorrectly, and was constantly trying to communicate with the watch to keep contacts and other information synced. This was draining the battery life on both the watch and the phone within an incredibly short time.
I deleted the gear manager program from the phone and reinstalled it. And since then, everything has been running smoothly, with my usual 2 days 1 night charge available for the gear.
I am now going to return the refurbished Gear S that they sent me, because I don't want to risk having somebody else's previous problem instead of my always kid glove handled watch. Although I would love to have a brand new battery. When I replace my s3 for charging port problems, the new phone did not work anywhere near as good as my original phone had, so I'm a bit gun shy on refurbished electronics.
And since this is probably too long for most people to read, in a nutshell...
Try deleting and replacing your gear manager on the phone. It will also wipe your watch back to factory settings, however this should make everything work perfectly. At least it did for me.