I have been using iPhones since the 3GS and never had a problem like this that I couldn't fix so I think it might be hardware but just wanted to get some other input. Have a 6s that had the battery replaced in December 2017 and the battery health is at 97%. I have downloaded no new apps or changed my usage in the past couple weeks. I didn't (knowingly) change any settings and can't find anything on that is draining my battery. For the past 6 nights now I go to bed at around 90% battery and wake up 8 hours later and I'm around 20-30%. I check the battery stats and it just shows my actual usage and nothing running overnight or in the background all night. I have tried a restart, tried beta software, back to public software, and even did a restore last night and set it up as new but same thing this morning. Could my battery somehow be defective even though it is showing at 97%? Any other suggestions?