I got an iPhone 7 basically on launch day and had terrible battery issues up until last week, when I decided I had had enough and went into the Apple store and

I got an iPhone 7 basically on launch day and had terrible battery issues up until last week, when I decided I had had enough and went into the Apple store and got quite animated until they finally agreed to swap the handset for a new one. Since then I've had no problems. Things I tried multiple times in different ways: Reset all settings Run battery to flat and then charge to 100% Restore entirely from backup Look at running processes with Instruments (normally MediaAnalysisD was pinning the CPU even when in standby) Switching basically everything off (background refresh, mobile data, etc.) Nothing made any difference at all. The battery was draining at roughly 1% every 8 minutes, even when it was in flight safe mode. In use, I would be at 20% battery by the end of the day, whereas my old 6 would normally be at 60-70%. There is definitely something going on that Apple can't work out, even when they run diagnostics on the handset. Their solution in store was for me to format the phone and run it with nothing installed, etc. for a couple of days. I basically expressed clearly how this wasn't an option for me after having paid so much money for a device that I'm reliant on for business communications and eventually they gave in and swapped the device, since then it's been a night and day difference. I get to the end of a day on 75%.