Why would Germany need to run solely on battery for 2 weeks? Do you expect 2 weeks with 0 sun and wind all over continental Europe?
In any case, at $100/kwh, it would cost $250bn (EDIT: $25tn sorry) in batteries and maybe the same in installation costs to power Germany for 6 months a year. At the lower $20/kwh price tag it would be more like $5tn, compared to Germany's ~$4.5tn GDP. Over 10 years it could be done.
(And 6 months' storage is maybe too much anyway)