Battery Issue - stuck at 100%

[Ifti]

My mother has an old iPhone 6 - she's not very good with tech and uses it just for the basics so it's always been fine for her.

The battery hit 75% health, so I replaced it.

Ever since it's been replaced it sits at 100% for 2 days, and then suddenly dies. It's like the battery works and holds charge normally, but just doesn't report the correct percentage, and hence just dies.

Each time it gets used and dies she charges to 100% (I told her to do this to recalibrate the battery), but even after a few full charge cycles it does the same - see image...

Anything I can do other then replace the battery again?

Thank you

 

[now i see it]

iPhone 6 on iOS 12 is absolute murder. I have one. It’s so painfully slow. True torture to use.
Punishment.
Get her a refurbished iPhone 6S on backmarket. It will come with a new battery and cost about $100. It runs on iOS 15.
It’s a superior phone and way way faster. I use one.

 

[BugeyeSTI]

Most likely an issue with the battery itself. If it lasts 2 days it sounds like it holds charge well, it just doesn't report it's state of charge correctly.. I'd say you should ask for a replacement or as @now i see it stated get a refurbished 6S instead

 

[StoneJack]

Broken battery