That’s no good!
I’d ping Google a message via the chat option in help just to see if there’s anything they can do. Doesn’t seem right for it to drop to that amount in such a short space of time.
Sounds cliché, but have you tried a factory reset?
I noticed some small gains after doing one shortly after the Pie beta finished. The restoration process is so much better than I remember on older devices. Everything came back exactly as it left off, even SMS messages.
I’m sure they’d just tell me to do a warranty repair from the merchant (in this case, EE… I think… or maybe Carphone).
I haven’t done a factory reset… I’ll see how it goes with the March patch and then maybe do that.
Try it anyway. Don’t ask don’t get 
Yeah definitely see how resetting goes. Android is notorious for becoming bogged down over time, so always good to have a spring clean!
Oh just to add, Ask Google assistant “my battery is poor” or something along those lines and it’ll go through some diagnostics.
March patch seems to have made a difference! I’m now at 40% after 11 hours or so. I can live with that 
Have you ever tried a whole day on battery saver? On the pixel 1 the phone will last about 8 hours. I can get over a day without it.
I had a similar thing.
I loved my Nexus 6 - probably the best phone I ever owned. As your review states though, as things have moved on it’s become slower in comparison to the new flagships (which is to be expected) 
Honestly though, still an amazing phone.
After 7 years with using samsung product, though I try something different. I wanted a smaller phone than my current Note 8, I went for the Pixel 3, there was an offer of £150 google store credit during the valentines weeks which I thought it was very rude not to go for it.
Best purchase I have made, the camera so much better than the note 8, it is much faster, the photo quality is clearer with both double lense selfie camera and with the single rear facing camera even at zoom mode.
The pure android experience is so much better, no bloatware and the os is much faster and smoother.