2001 740il battery/electrical problems

Several times recently, I've been driving down the road and my engine simply cut out--died--power steering gone the whole works. The first time, I was able to pull over and restart; the second time, I was on the freeway and the engine cut out for a second or two and restarted, and today it cut out again. I had to pull over and restart. The battery shows black indicating that it is insufficiently charged. Load tester shows 12V. I'm currently charging the battery to see if it holds.

Any ideas for troubleshooting would be appreciated. Alternator? No warning indicators appeared, not even low battery indicator.
Thanks.

Even if the charging system is bad (battery,alternator), the car should not shut off while driving without giving symptoms first. If the car shuts off in the street, something is cutting off fuel or spark. You should check fuel pressure, and scan the computer for error codes.

Thanks very much for the help. I'll check it out.

i know the electronics in these cars are sensative. could low amperage output of a battery cause this?

Honestly, I don't think so. If the alternator died , the battery light would come on the dash, and it would take time to drain the battery, and if the battery died, the car wouldn't turn over afterwards.