Here's why 9.3.1 is killing the iPhone 6S Plus battery (in my case)
As per title, this is - I'm convinced - the reason for the dwindling battery life on 9.3.1. I'd be very interested to see if it is the same for you..
Just to give you some context - I had the original 6 Plus and then migrated to the 6S Plus back in September. Been using both with Apple Watch. Both had outstanding battery life compared to any phone I'd ever had before. I'm just explaining this so that you can see I am familiar with the great battery on this model prior to the issues that appeared. Back in April, I took the maddening decision to switch to a Samsung Galaxy S7 Edge. It didn't last long. The battery couldn't hold a candle to the iPhone. I sold it and bought a new 6S Plus. An expensive mistake, but we'll gloss over that..
So I went back and with the updated 9.3.1, pretty much straightaway noticed the battery wasn't as great as it had been. Standby usage still exemplary. Don't touch it, and it will sit on 100% for three hours. Don't touch it all day, the battery will barely move. Great.
But use it, then the battery drops quite quickly. At one point, in just two mins of using the camera to take photos, it dropped 5%. And the battery would often drop in 2% increments at a time.
First thing I did was an over the phone diagnostics and Apple told me there were some apps drawing more power than they should be but they couldn't see which over the phone and advised a Genius appointment. The girl in store ran a check and showed me that there were issues with a large number of apps - they were crashing in the background, then (I assume) automatically reopening and crashing again in a never ending cycle.. She said it was this 'constant behaviour' that was draining the battery. Important to point out here, they were both third party apps (Addison Lee, Checkmark 2, British Airways, Instagram) and stock apps (Weather, Reminders, Stocks etc - I don't EVER use Stocks, FYI!). Also worth noting that these apps were not showing up anywhere in the battery usage section in settings. Nothing odd showing up there.
Suggestion was that I could do a backup and restore but that could bring the software glitch back. Or just cut my losses and do a brand new setup. I opted for the latter - and in the process, lost 18 months of messages etc.
Setup as new iPhone without restoring from iCloud. Problems persisted.
So I decided to go nuclear. Removing the iOS source file from my Mac so that iTunes would have to download a fresh copy, wiped my iCloud compeletely so I had NOTHING in there, stopped apps from backing up to iCloud, then wiped it again. Then set up the phone as new again from scratch. This was, to all effects, a virgin phone.
And still, when I took it back to the Genius Bar a few days later, the problem was manifesting itself. Apple were adamant it was a software issue, nothing to do with the battery, but as we had exhausted all possibilities, they gave me a brand new iPhone. And once again, I did a full nuclear-level install as a new phone.
And what do you know? The battery is still below par!! And when I took it in, the Genius ran a diagnostics test and it is still the same issue (some of the same apps, some others - a real selection!).
The battery no longer drops in 2% increments, but what it does is sit on one number for a while d then goes down several percent very quickly. It is no longer the reliable phone I had. And it is driving me crazy. Had I not spent 18 months using this device and being awed by its battery, I wouldn't have noticed. But I do because I know it is so much better
I thought it was just me but a friend with the same phone reported the same thing although he hasn't been to the Genuus bar so doesn't know if it is apps crashing causing it as it is with me. Without going to the Genius Bar, it's a problem you could all be having and not realising because it is not manifesting itself in the Battery Usage settings area. So you would never know.
I am no expert on operating systems, but I had a root through the Diagnostics and Usage area of my settings and I can see that apps are still crashing as of now.
Be interested to see if this is an issue with you guys too?
Couple of footnotes - I'm not jailbroken, I'm not using my phone any differently to before and I'm not downloading tonnes of new apps.
Have a great day.