Car went dead all of sudden while driving - started right back up

[mdat25]

Hay folks,

This is a strange one! So last nigh I was driving and minding my own business when all of sudden all the lights in the dash went on and the car just went dead. No power - I mean no engine and no electrical power.

I pushed the gear into neutral so I could roll to the side of the road and just thought what the heck let me see if it will start back up. Sure enough it started right back up! The radio (time) and everything was reset but the car did start back up.

I checked the battery voltage through the dash tests, and on idle (car off) it is reading 11.1v. I know that's low so I am gonna get the battery replaced today. But I am not sure if that could have done it. Besides this is the battery the car rolled out of the factory with so I am surprised it has lasted this long.

The only thing that MIGHT have something to do with what happened is that a few days ago I had the engine compartment washed at a local car wash. I already checked (as far as I could reach) around the alternator for loose connections and there doesn't appear to be anything wrong. Besides I have been driving the car for 3 days now since the wash so if there was anything really loose then I guess I would have known it sooner?

BTW, this is an E53, 2002 x5 3.0 I6, 88k miles. Have had this car for 6 years now and I love it. I remember reading once that these cars have faulty "junction boxes" but have no idea where that is - let alone WHAT a junction box is!

Any help will be greatly appreciated.

Patrick