Well, I'm not sure what you're trying to accomplish with "Sybase Central" and batch files, but remember that Sybase has a 'backup server' which you use to make backups.

Ensure the backup server is running (sounds like you're on NT, go into services and start {your server}_backup if it isn't already running) and then run:
DUMP DATABASE whateverdb TO "c:\wherever"

If you have ISQL on the box you could run ISQL from the batch window which then issues the dump database command (you'll probably have to place it in a text file then tell isql to run it).