I spent all day downloading all my unread books from Audible onto an SD card, thinking I could just plug it into my car (2018 Porsche McCann) and thereby free up my phone. But when I put the SD card in, it said no playable files. Sounds just like kindle books, before Calibre. I can play the books just fine from my phone, but it ties it up and uses the battery. There is a jukebox and SD card on the radio, but neither would play my SD files. I have found a very old ipod, and once it charges I will download my books into iTunes and play that through apple play. But there must be some way to get the audible files I own un DRMed so I can play them in the car.