There seem to have been a number of similar queries about cheap ticketing in Germany . It is always worth genning up on the tariff areas of Germany (and other countries such as Switzerland), as the regional tariff areas are where you tend to get 24 hour ranger tickets etc
A long exhaustive wiki kist:
https://de.wikipedia.org/wiki/Liste_deutscher_Tarif-_und_Verkehrsverbünde
and a load of stuff here:
http://www.vgn.de/0F336936-BB07-11D7-AE44-00034709FE0C
http://www.nahverkehr-info.de/verbund.php
.
A long exhaustive wiki kist:
https://de.wikipedia.org/wiki/Liste_deutscher_Tarif-_und_Verkehrsverbünde
and a load of stuff here:
http://www.vgn.de/0F336936-BB07-11D7-AE44-00034709FE0C
http://www.nahverkehr-info.de/verbund.php
.