FYI IOS 11.4
I updated to 11.4 a week ago and since then I have experienced terrible battery life, often needing to recharge every 3 hours of light use. I have a new replaced battery from APPLE's battery deal for iphone 6's.
What I found searching is you have to disable 5ghz wifi and use the 2.5. Since then my battery life is back to normal. Hope this helps someone.
Wow. Bizarre. I, too, have noticed reduced battery life on my iPhone X lately. I thought it had to do with all of my picture/photo-uploading apps that I've been testing (and mentioned in MGG 714), but... wow. How did you turn off 5GHz?