grober
MB Master
Found this usefull PDF on the W211 dual battery system. Adobe comes up with some errors but if you persist some useful info.
http://www.mercedestechstore.com/pdfs/W211_advisor/219 HO Dual Battery (ACB - ICC) 11-29-02.pdf
http://www.mercedestechstore.com/pdfs/W211_advisor/219 HO Dual Battery (ACB - ICC) 11-29-02.pdf