Google removed the watch battery stats from the Wear app some time ago, but it wasn’t really much of a loss. They were borderline useless at the time anyway. In the latest version of Wear (1.4.0.2470307.gms), the battery stats appear to have returned. As to whether or not they’re still junk, I cannot say yet.
The battery stats are right where they always used to be in the settings for the watch.
Latest Version Of Android Wear Brings Back Watch Battery Stats [APK Download] was written by the awesome team at Android Police.
Source: Andriod Police