I bought a 12 Mini a couple years ago to be the shared phone the kids would take if they were out somewhere that we wanted to have communications ability, and it came with a third party battery. It hasn't been awful, exactly, but the life on the battery seems very low even for a mini.
(every time I pick up the 12 mini, I feel tempted to find the nicest 13 mini I can find and set it up for myself. what a fantastic size, makes my 17 pro seem huge)