iPhone XS shutting down with 30%+ battery remaining

Sure, there's no arguing that batteries chemically age over time, but where I disagree is that after 18 months it's acceptable for a battery to become totally unreliable, and that the only cure is a new battery.

The "don't charge past 80%" was also a method endorsed by Apple, but I didn't pose my original question to discuss physics, chemistry, and charging approaches. The question was is there a way to recalibrate the battery level software so it more accurately reads the battery capacity and prevents flukey shutdowns at 30%. Responses have not been helpful.

To get back to that question, I seem to have gotten the phone battery recalibrated. Was able to run the battery down to 0% before it shutdown and then charged to 100%. Believe it was one of two things. The first thing I noticed was when I went to make a backup of the phone storage on my computer, the computer downloaded diagnostic data. Don't think that did anything but it was a new observation for me. Guessing the MacBook just downloaded that info from the phone, and didn't doing any diagnostics. Next thing I did before doing a factory reset was update software to 14.6. After those two things, I was able to run the battery to 0 without it shutting off prematurely. It's been doing fine ever since, and not shutting down with 30% battery left.

So guessing the software update got things straightened up for me. Whether it was a bug fix in 14.6, or just resetting the phone data on battery capacity in parallel to the software update, I'm not sure, but problem solved. After all that, the battery does now say 91% capacity but still is able to maintain peak output.

Why would the battery capacity number on the phone be incorrect? Have no reason not to trust the information from the phone. It squares with the ranges I've seen others report and the battery is supposed to be able to function at peak performance.

FWIW, I've been pretty judicious about charging the phone, typically keeping the battery between 20% and 80% charged.

Given the dying at 30% and the typical charging range, it would seem the software/hardware needs to be recalibrated, as is in when it says 30% it's closer to zero. Is there a way to do this recalibration? Is there any substance to say the procedures here:

https://www.iphonetricks.org/how-to-fix-iphone-battery-percentage-bug-in-ios-14/

Or will a factory reset potentially help at all?

I just have a hard time buying into a less than 2 year old phone needing a new battery.

Time will tell, but I think it's mended...at least for now.

Thanks for the reminder about the Coconut Battery app. I'd read but forgot about it.

Hey there, when I ran the coconut battery ap, read the iPhone at 90.4% and 389 charge cycles.

So not exactly the same as the software on the phone reads, but pretty close.