The Huawei Watch got through the entire day, which started at 8:30 AM an ended around 1 AM. At the time I put the watch on the charger it had about 8% battery left.

I am pretty sure it would have had more battery power left on a normal day, because yesterday was the first day I was really using it, I spent more time than normal using it, changing watch faces and trying out apps. 

The watch's battery drained more quickly when I was charging my phone because during that time it was not connected to the phone and apparently kept trying to connect. 

I've noticed this same behavior with the Moto 360, and I haven't figured out whether the issue is being caused by connecting my Nexus 6P to its charger, and it rapidly charging, or the location where it is charging which is on the desk in the main floor of my house rather than in the basement where I was working. 

Actually, I suspect the issue may be with the bluetooth drivers on the Nexus 6P , or rather the bluetooth drivers that come with Android. In addition to connectivity issues with the watch, it also sometimes has problems connecting to the bluetooth in my car.