with which encoding is my sdcard mounted by android?
You can find out by issuing the command mount at a terminal prompt (either via adb shell of using any terminal app). As I have no access to your sdcard, I cannot answer the question for sure (I could only tell you about mine, where the relevant parameters are set as codepage=cp437,iocharset=iso8859-1,shortname=mixed,utf8. So it's "Latin-1" (ISO-8859-1), which seems quite logical with a FAT file system, and probably is also used in your case.

Full list of options:

rw,dirsync,nosuid,nodev,noexec,relatime,uid=1000,gid=1015,fmask=0002,dmask=0002,allow_utime=0020,codepage=cp437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro