Why is iOS 11 draining my battery?

I am having the same issue. My iPhone 7 Plus used to go all day before it even came close to reaching 70% on the battery. Now, only after a couple of hours my iPhone will drain down to 70% or lower! I never had this issue until updating to iOS 11. I have tried all the tips to prevent battery drain but to no avail. What the heck is going on?! I had a iPhone that could stay charged a day and a half, now I have an iPhone that is lucky to last half day.