Your truck was running with w/o an alternator when battery light was on and before the battery was depleted, so it should start and run w/o alternator present. Code(s) will likely be set because DME can't communicate with voltage regulator. On some Bimmers the CAS-DME alignment needs to be re-sync'd after running or attempting to start with an undercharged battery. This is part of the X5's theft prevention system. INPA/ISTA/Foxwell can re-sync if needed.