https://www.cnbc.com/2017/09/13/apple-watch-series-3-has-one-hour-battery-life-for-phone-calls.html

The Apple Watch Series 3 has pretty weak battery life if you rely on it for placing phone calls.

That's one of the highlights of Apple's new watch — the ability to place and receive phone calls even if you leave your iPhone at home — but doing so will drain your battery at a rapid pace.