I have a 2006 325i that apparently needs a battery, the dealer offered me a replacement around $400, of course this is not covered by warranty. I've been told that the battery is massive, that it will need to be registered? I've called around a couple of places from the magazine and have gotten quotes from $270 to $149 my question are why is the battery so expensive and does it have to be registered and what exactly does that mean?? Help!!