My iPhone 7 has battery issues after I installed the update. I know of one other person that experiences the same issue. My battery drains in less than a few hours compared to a day or more before I installed IOS 13.xx or whatever the first release was. The subsequent updates have not fixed any problems.
These battery issues are usually resolved by forcing a complete cold start which clears all the registers. Have you done that? If that doesn’t do it, then the next point or so upgrade usually fixes the problem.
Finally, have you ever replaced your iPhone 7’s battery? The iPhone seven was released more than three years ago. That’s about 1,150 charge cycles ago. Lithium Ion batteries are supposed to last only around 750-800 charge cycles. So, if you are like most people and put your phone on charge at night after a day of use, your phones battery is bound to be getting a tad long in the tooth!
This quicker depleting could be just coincidence because your older battery was already in need of either a cane or a wheel chair to do what it was used to doing, and with a new iOS with its newer capabilities, the older battery isn’t quite up to the demand and therefore gets pooped out faster, while a newer, younger, chemically-undepleted battery would be fine. Worth a try.
Cheapest way to do it is with a Do-ItYourself battery kit you can buy from Amazon for under $20. . . or you can have a pro do it at your local Batteries+ stores. . . and BestBuy can do it, usually around $70. Apple charges $99.
Your phone must not have an eom battery in it. The last update blocked any battery other than apple approved ones from charging correctly. I was on my second battery for my 6 plus before I broke down and upgraded to Iphone 11 2 days ago.