MagSafe battery back stops charging after 100%
Got myself a used iPhone 13 mini with a MagSafe battery pack. Everything works fine except for one thing: when I put my phone on the battery, it charges to 100% and then stops until I remove and reconnect the phone. I did a test yesterday: the phone reached 100% as usual, stopped charging, and I left it overnight. In the morning, the iPhone battery was showing 73%, which is way below any charge optimizations that might have triggered.
What's wrong with it? Should I update battery firmware maybe? Or it's just faulty? Or maybe it's ok and I see intended behavior? Tried to connect this battery to my mbp but it seems quiet and nothing happens. When I connect it to a phone, battery widget can see the battery, but I can't see the battery in settings or anywhere else.
iOS 26.5, iphone has been reset to factory defaults a couple of days earlier.
UPD: solved, battery is a fake one