On my previous 3.0i 2003 battery died w/o any real warnings some weeks ago. I needed to tow car to dealer (good that I paid extended BMW roadside service - free tow). Even the strong original battery it does not really give any warnings before it dies. We were sitting on school car line when worst happend - X5 is pretty heavy car to push and stear w/o power. If you have any indications of weak battery, change it sooner than later. Dealer took $250+ to put original battery in.
