German Battery Act (BattG)
According to the German Battery Act (§ 9 BattG) batteries can be returned free of charge to the sales outlet after use.
Please, consider this sign § 17 Absatz 1, batteries with this sign are not allowed to be put into the regluar waste container:
Pb = Battery contains more than 0,004 % sinker
Cd = Battery contains more than 0,002 % cadmium
Hg = Battery contains more than 0,0005 % quicksilver.