Please note: Since I wrote this, I started having issues again. I'll update as I find out more.
I trialled a Moto 360 when they were on offer earlier in the year, and while Android Wear was okay in itself, I wasn't too impressed with the shape, but more importantly, whenever I had the Wear application on my phone, it utterly murdered my battery. Weirdly, it was Hangouts that was keeping one core at 100% all the time, which I found quite odd, but never managed to find an explanation, or get to the bottom of it, although I did submit some bug reports.
Fast forward to now, and I'm back on Android Wear, having accidentally smashed the glass on my SmartWatch 2. And lo and behold, my phone battery was being eaten for breakfast, again, and yet again it was Hangouts.
Much experimentation later, and I finally realised the problem - I had too many active hangouts. Being an Ingress player, this is nothing new, I'm used to having 100+ on the go, but all those hangouts with individuals and groups took their toll when trying to sync. My guess is that the Wear application was trying to sync the huge amount of data to the watch, and kept failing, and kept retrying. I archived off all my non-active conversations. Boom, watch syncs up without falling over and eating my battery on the phone. Victory!
Hope this helps other people from scratching their head as to why their battery life sucks after getting an Android Wear watch, and if they've spotted Hangouts taking up a crazy amount of CPU. Once the initial sync is complete, it seems to have behaved since, but time will tell if that stays the case.
Do let me know if this has affected anyone else out there, or if it's just me...
Edit: Unfortunately, it appears that it was actually the act of clearing the data that solved the problem. After a while, it seems to get stuck again and constantly try to resync with the phone. It's rapidly putting me off using Hangouts altogether, which is a bit of an issue when most of my Ingress game communication is done on there!
Noted another thread relating to this:
https://www.reddit.com/r/AndroidWear/comments/49u6m4/high_hangouts_cpu_usage_since_getting_watch/
Will add more as I find them. This is maddening, there seems to be no source of information on it. Just installed Messenger and disabled Hangouts SMS integration, let's see how we go...
