How is 10.2 treating you in terms of battery life? I remember when 10 first came out I could watch my battery die in minutes with little to no usage. I have a 6S+ here and it seems like the 6S family suffered the most from battery issues due to software.
LOL if your battery dies "in minutes" or a very, very short time then it's most likely an issue with the battery itself and it should be swapped for a new one. Respectively I'd try a reset and clean install of IOS without using the backup first and test it to see if any app might have caused this.
A relatively new battery with a couple of charging cycles in a 6s should at least last 24 - 36 hours with the following criteria:
-
good cell phone coverage
-WiFI turned ON
-BT turned ON
-locations services ON
-background updates (apps) OFF
-moderate use: phoning, Facebook, mails, internet, music, the occasional YT video,
NO gaming
Since the 6, which I still own the battery is pretty decent, my girlfriend has the 6s and has about the same use case as me with about similar battery times. IF the cell phone network coverage is bad though, meaning the phone is often changing from LTE to 3G or E and back which is the case in my office building my battery lasts about 20 - 24 hours.