Sorry, sounds typical dealer BS. A four year old battery is likely the issue. What do they want to charge for this "test"? I would bet a lot of $$$ that after they charge you for two hours of labor + they come back and say it's the old battery after all...
2011 Space Grey E90 M3, DCT, Comp. Pkg.
1997 Z3 2.8, Artic Silver, Tanin Red interior, MT
1974 2002tii, Inka, MT