On iOS 11.3 or earlier, my X used to give 4 hrs of screen time from 100% to 60%. With 8-10 hrs of total screen usage.
As of iOS 12 (all versions), my X (earlier 100% battery initially on iOS 12, now 97% battery) comes down to 60% in about 2.5 hrs of screen usage with a total screen usage of 5-7 hrs with similar usage.
My 7 met the same fate as iOS 10/11 progressed. Initially 8+ hrs and later barely 6. With a near fresh battery.
My mom’s 7 started with 9 hrs screen usage and is now down to 4ish with a 100% battery on iOS 12.
Many of these devices have been DFU restored and started clean without a backup.
Happens across every single iPhone.
Will happen to XS series as the year progresses. And so on.
It’s still at 97%. That’s not really tangible degradation at all.
Here are my thoughts and things I have noticed. First of all I had iPhone 7 before and I did not notice different operating time when upgraded from IOS 11 to IOS 12. Then I bought X just couple of weeks ago and I have been monitoring battery life because it looks like I need to charge it much more often than previous phone.
Also another family member has the same models, so I have something to compare with.
In short I think there is huge variation between batteries used in the same models, even based on battery capacity monitoring they all appear excellent.
For example my X came out of the box with 2782mAh battery (nominal is 2716mAh), but as soon as after first charge it lowered couple tens. Another X came out of the box with 2884mAh battery (so about the same) but after first time charging it did increase to around 2800mAh. Also difference between the two was that mine came out of the box with pretty empty battery (around 1/3ish) while that other was around 3/4's. So obviously mine did lose quite a bit charge while sitting in box.
Anyway things I have noticed between the two new phones is that mine need to be charged pretty much daily while other one goes easily 2-3 days. Another peculiarity between the two is that even they appear to have similar battery usage when doing some test, in the end there is big difference in how often they need to be charged. I list three different situations.
1. Like when I have been testing them several times by surfing on the internet with Safari for certain amount of time with same screen brightness they have usually both got the same result, about 10-14% per hour. There was couple times when mine did during that test drop suddenly 2-3 at the time while that other always goes down by 1% at the time, but I cannot recreate that thing with my phone when I try it intentionally and most of the time I get the same result on both. So based on this they are equal.
2. When leaving them on for night say 8-9 hours when they are not touched even once, they usually result both 5% battery use during that time. Sounds again normal between these two but that is not good compared to 7's since it was about same but those have smaller battery (screen do not explain difference when it is not in use during that time).
Anyway, based on this both new phones equal.
3. My phone very often does that when it has not been used and I pick it up, drops 2-3% pretty fast. Like overnight it dropped 5% but as soon as I pick it up it goes down 1%, then within a minute another 1% and then stabilizes during under first 5 minutes by dropping maybe 1% more (so total 3%). After that is seems to drop 1% after every 5-6% during use. But that another X usually does not drop in the beginning like that and most of the times I tried it, it did drop first 1% after few minutes and then again with rate of 1% every 5-6 minutes during use.
So in this they are different and I think this explains why mine need charging more often.
Again these are my initial findings and based on battery usage times mine has been used approximately 3 hours a day during past 10 days and that another 2 hours a day during past 10 days, so mine gets more use but still when you consider how often they need charged is so different, and I guess that third example above may cause the difference.
With my previous 7 I got easily 2-3 days between charges but with somewhat less use (new device gets more attention).
So my conclusion is that when battery meter capacity report or more detailed report (like iMazing or Coconut Battery) shows any degradation, situation is much worse in real life. As seen many times peoples reporting battery problems with even well over 90% battery capacity (based on monitoring sw) do not work well and operating times are short.
As far as I have understood 80% battery capacity means battery is EOL and it definitely does not mean battery still has 80% operating time of the new one, neither does anything above that have any relation to actual operating time.
