BMW Z4 2005 2.5L WILL START WITH A BOOST AND A CHARGE BUT FAILLS TO GO TOO FAR BECAUSE DOES NOT RETAIN THE CHARGE. BATTERY SHOWING 11.5 AND THE ALTERNATOR SHOWING LOW ALSO , BUT I HAVE CHANGED A BRAND NEW BATTERY , OLD BATTERY ALSO SHOWING WAS GOOD , CHANGED THE ALTERNATOR ALSO, CHANGED THE STARTER ALSO. SO WHY DOES NOT RETAIN THE CHARGE , IS THERE A ALTERNATOR RELAY OR STARTER RELAY OR ANY KIND OF FUSES NEED TO BE CHECKED?
WHY NOT RETAINING THE CHARGE