Battery issues

That is not brilliant battery life, I might expect 92% at 9 months, but that is the warranty you agreed to on purchase. You could have purchased AppleCare+ to push the battery warranty to 2 years but you balance that cost against $69 for the new battery which looks like being 18 months - not too bad, two years being a more likely time.

All batteries age with use, just that Apple chose to give you an approximate capacity compared to new, but had the misfortune to name it "Health"

Charge it all night every night and don't let it run flat to maximise battery capacity.

This issue seems to be arising with more recent phones and since the facility to read off the battery health was made available. My wife's XS has done something similar. However my 2016 SE is now on a 3rd battery which has remained at 100% for a year! Can this be the case? The true test is just to observe how your phone is performing in day to day experience. In my wife's case she seems to be happy with battery life and hasn't commented on any serious issue.

I would keep a close eye on that 80% mark and then head off to the Apple Store. It is actually a small reason I have held on to the 2016 SE as I can change the battery myself with minimal expense in about 15 mins.

Did Apple replace the batteries? Third party (ie fake) batteries can often always show 100% or nothing at all.

We also have reports of some batteries just never shift off 100 but the vast majority lose 1% every 4-8 weeks.

I replaced the batteries using an iFixit kit the first time and then an oGoDeal Battery Replacement for iPhone SE 2350mAh the 2nd time as I was not so happy with the iFixit battery. It's not been possible to access Apple Stores during the pandemic in the UK and I have been less than confident about using some of the 3rd party 'approved' repairers they recommend who are all located a long way from my home.

I think it's likely that my battery is just not being reported correctly and is, as you suggest, sticking on 100%. Nevertheless it has performed better than either the original or iFixit models which is interesting. Thanks for your clarification.

Those batteries are all fake and you are lucky to get a health reading at all but with unknown chemistry any reading is suspect.

If you didnt need the phone for a few days the mail-in repairs were available.

Problem now is Apple will not touch phones repaired by third party, and regular forum members will not offer help on here.

Well it's a 5 year old SE bought on Day 1 we're talking about so I have no complaints. The iFixit battery did give a health reading and perhaps I will return here to note if the present one starts to read less than 100%. The phone received iOS 15 and is still working very well. I spent my available money on an M1 Mac so the phone will have to wait! I appreciate your comments and advice.

You're welcome and congratulations on reaching level 2