Two problems related to battery have been reported for the 2004 BMW 530. The most recently reported issues are listed below.
Car was going to be purchased on 8/24/2012 was told to drive for the weekend. On 8/27/2012 around 3:00 in the morning (after filling with fuel the prior evening) we heard a loud explosion, then followed by firetrucks and ambulances. Upon inspection the BMW in the parking garage was engulfed in flames, windows had blown out. According to fire marshall fire started at battery in trunk and was ignited by gasoline vapors. Caused major fire damage to car parked next to it as well.
Driving north on I-77 in s. C. - traveling along with the traffic flow - left hand lane - suddenly alert lights came on that abs was not operating, battery alert (had battery installed at dealership) etc. - engine quit - dash board went blank - was able to get to the curb lane (no turn indicators) came to stop - tried to restart -no luck -wait maybe 10 minutes it restarted -drove home -approx another 200 miles -dealer could not find any problem - it could have been a dangerous situation if someone panicked.