Hi Roland,
Are you specifying a file to use for the log? This command line works for me and produces log files between 3MB and 50MB so far (depending on drive size and number of files/folders):
 
	
	| start "Updating ClamAV..." /realtime /wait bin\freshclam.exe --verbose --stdout --datadir="db" --config-file="bin\freshclam.conf" --log=%ECSFOLDER%\clam_update.log ECHO.
 ECHO  * Run ClamAV
 start "ClamAV" /realtime /wait bin\clamscan.exe --verbose --stdout --database="db" --log=%ECSFOLDER%\clamscan.log --remove=yes --memory --kill --detect-pua=yes --scan-mail=no --scan-pdf=no --scan-html=no --scan-archive=no --recursive %SYSTEMDRIVE%
 | 
HTH,
Drew