Assuming the device does not draw more then 500mA, it comes down to which filesystems that BMW supports.
Look for the maximum filesystem size
http://en.wikipedia.org/wiki/Compari...systems#Limits
Possible filesystems that they *may* support: FAT16, FAT32, exFAT, HFS Plus
Somebody already commented that NTFS apparently does not work.
For instance FAT32 filesystems can be up to 2TB, but you may have problems *creating* such a filesystem larger then 32GB
*edit*
ohh and be aware that you can either format a device directly with a filesystem, or partition it and create filesystems on it.
Not everything supports partitioned devices, and even if they do there are different partitioning schemes...