The iPhone 12 lineup has some really bad battery health overall... my old refurbished 12 Promax dropped from 98% to 85% in 3 months of usage by charging it one time every 24 hours and also sometimes one time every 48 hours... most 12 phones have like 72% health after just 2 years of usage instead of around 85-88% Also, yeah... if your phone was actually new in seals, etc, that doesn't mean it's actually "new" Phone could've been sitting in a box for a long time unopened before getting it sold to you ( because iphone 12 lineup is discontinued) Battery ages even if you don't use it !!