apple watch draining iphone battery

I have a new 44mm watch which replaced a 38mm. The 38mm watch performed flawlessly and I encountered no problem with battery charge on the (6s) phone, which I continue to use. As soon as I activated the 44mm watch, the phone battery discharged within 10 hours. That never happened before no matter how long the day or intensity of use of usage. What's up with that?