I've had my E39 one month. 2000 528i with 146k on the clock. On the second day I had the car, I had to replace the battery. Since then it has run well and started easily every time. Today after work I started it, and the battery light stayed on. I thought it was a glitch but after a restart, the light remained on. I checked the battery voltage with a voltmeter and it was 11.7 V with the engine off and with the engine running voltage was the same. I'm assuming this means the battery is not being charged. I left the car parked overnight where I work. It would still start but I knew it should not be driven. Tomorrow I will return with a battery charger. I'm hoping to charge the battery up to about 13.2 V and then drive it to my independent mechanic (a former BMW dealer tech, located less than 2 miles away), and have it diagnosed/repaired. I'm assuming it's the alternator, but could there be another (and hopefully less costly) explanation? I know the Prince of Darkness for old British sports cars is called "Mr. Lucas" but what about for Bavarian cars? Any advice would be greatly appreciated.