OK this isn't for my Alfa, but I thought someone might know. The battery in my wife's c class is dead (5.7V). I couldn't unarm the alarm and now the alarm is periodically going off with the back up battery for the siren. If I disconnect the battery, the alarm goes off continually. Can I hook up a charger onto the battery purely to unarm the alarm system or will this fry anything? I'm not talking about starting the engine. If I don't get it unarmed, it will go off all night I reckon, and i suspect the neighbours will want there christmas cards back. Anyone know?