There seems to be an interval in which the app actively actively polls data from the car. It defaults to 4h and only during daytime.

I guess if you set that to a very short internal and the car is not currently charging (at which point the 12V battery does nothing) there could be quite some battery drain.

That said, draining the 12V battery of an EV to the point where you get problems seems difficult.

I found a free and foss alternative to OpenAudible that seems to work fine: https://github.com/audiamus/BookLibConnect

There’s a sister project to convert the aax (m4b) files, but I found that to be unnecessary.