I had this problem after I updated the iOS the very first time. We received our preordered iPhone 7 devices 9/19/16 & 9/28/16 in the 2nd Verizon batch of devices sent out. From what I know to be true in my situation, and according to Apple support early on, it was an iOS defect causing the battery issues with the new iPhone 7. My son got the iPhone 7 Plus and never had any battery troubles that we know of. I ordered my sister the iPhone 7 and she got lucky enough to get hers a week prior to us on 9/19/16... she had the extremely hot battery issue when charging it or using it for extended periods of time... abnormally hot and uncomfortable to even hold onto! Everyone uses their device a ton when they first get it because they're playing with the new features and seeing all that it can do... so we gave it a few days before panicking and taking it in for a replacement. However, my device did not get hot like hers but both our devices both had serious issues with the batteries draining within a half day of use, and was driving us nuts. We were told they recommended resetting the device, and doing an iOS update, so we did that at the same time. Once we did a full reset and doing updates to our devices at the same time, and then checking our settings to make sure that apps were only running "While Using" and not set to "Always", it helped tremendously! They both actually stopped having the battery problems and worked great after that. Her phone hasn't gotten hot like it did originally and both our phones lasted more than a day of battery life. Both our devices are still working great without reoccurrence of the problems. While my sister's device had the hot battery issues early on, I really thought she would have more issues later on, but thankfully have yet to see it resurface. I finally figured out that doing a full reset of the devices may have helped as well.... not entirely sure of what did the trick, but those were the steps we took that ultimately resolved the problem entirely. I'm pretty confident that it was the iOS update after the support we sought out to find out what was going on. Neither of us have had any issues since. I do want to mention though that I have had the Beta software installed on my device since the beginning, but my sister does not... so I don't think it matters which software you are running. Currently I am on Beta 10.2 Version 14C82 and I can say that I've been very lucky with this batch of Betas... I had some battery issues with my previous iPhone 6s with the iOS 9 Beta software... but haven't had any problems yet with this new iPhone 7 while running the iOS 10 Betas (other than when I first got it and think that was from the first release of iOS 10). I was told by Apple that they know there is an issue with the battery getting hot on the iPhone 7 and the poor battery life , and it seems to be a software bug. Try resetting your device (a couple of times if needed), then make sure to check your app settings to make sure you don't have a ton of stuff running all the time in the background, and then update the iOS (or get the Beta if you are desperate enough to rule out the iOS as the problem).. I would assume this will resolve your battery issues. If these steps don't work, then I would take the phone in for a replacement.
