I also had major battery issues after updating my 6+ a couple weeks ago, but somehow they've resolved now. I'm not sure why or how things got better. At first

I also had major battery issues after updating my 6+ a couple weeks ago, but somehow they've resolved now. I'm not sure why or how things got better. At first I could see the battery power dropping in almost real time. Using safari for a few mins would bring me from 90% to 80%! (Eg - more than 1% drop per minute). I then disallowed almost all apps permission to refresh in the background. But that didn't really help much. I also noticed the phone seeming warmer than usual. But I wasn't sure if I was imagining that, being biased by the quickly-depleting battery. Agreed that the battery usage tool isn't very helpful. I think it just shows which apps were used by % of time in foreground, not by multitasked allocation. Eg, this was dominated by Safari and mail for me. I also let the phone completely discharge a couple times and recharge fully. Some people say this can help condition the battery, though I'm not sure how much truth to that for these batteries. But after a few days things just went "back to normal", and I went back to getting a fully day's use of charge. I haven't changed my permissions back, so most apps remain without background execution priveledges. I haven't noticed any limitations to my productivity with this change. FYI - I basically charge my phone daily, overnight when I go to sleep. I'm usually around 20-30% when I plug it in for the night.