So I got my phone like 3 months ago in December 12 from not authorized apple store, we dont have as i think, and it got to 96% on past month and now when I looked it has 90%. I wasnt charging from 0-100, it was 20-90 always, like I didn't treat my old iphone 7 that well and it was absolutely 2 years of heaven. only differences between them are that this one is factory changed iPhone XS and old one was with real iPhone factory made materials and didnt charged anything, SO IS this problem that I have bad battery or the phone is badly factory upgraded. tell me what to do in reply's thanks and have fun.