How many days can the X sit w/o battery dying?
 

3 days is the most I've gone so far. Anything close to 4 or 5 and I might as well go ahead and break out the battery charger.

My X5 sat for about a mouth and half started up like a champ.

Everytime it breaks and I order parts, it usually takes 3-5 days to get the parts. Everytime I start to work on it . . . dead battery. Battery is only a year old and I fully charge it everytime if find it in this state. I have been careful to check to see if anything was left on like dome light, cell phone charger, etc. and nothing ever found. I don't even set the alarm since it is sitting in the garage. Something is juicing it while it sits . . . I guess that will be my next X repair.

Do you have an aftermarket alarm system? They are the common causes of drain. The weather also is a factor. AFAIK, most bmw will go in the sleep mode after 15 minutes and the battery drainage should be minimal and should hold charge for at least a couple of weeks if not much longer.

No aftermarket anything . . . vehicle is completely stock. No alarm or any kind of electrical additions of any sort other than cell phone charger but I have developed a habit of removing it while not in use or if vehicle is off. Weather has been relatively warm lately . . . in the low 60's at night and high 70's in day. Haven't felt a chill in the air for weeks now. Something internal has to be draining it. I have noticed that on day 4 that only one taillight and only one front sidemarker light comes on by themselves and stays on until battery is completely dead. These lights are what I use as the sign to break out the battery charger.

my x sat for about 3 months and still started on 1st try.

I see. In that case my first assumption will be that there is a shorted ground somewhere. based on the side-marker issue you stated you may want to check the wiring at the rear tailgate hinges and the hood hinges. I had a similar symptom on my 850 and it was the broken ground at the trunk hinge.

Maybe worth a look? At least I'd check it if it was my car.

BTW. How old is your battery? Have you had it taken out of the car to test it?

Do you have bluetooth?

Thanks for that tip Ahmed303. I will check those two areas for wire damage.

Battery is 1 year old. I had it charged and tested by Autozone's fancy machine about 4 months ago when my alternator went out and battery tested good. When alternator went out and vehicle died it also had the one taillight and one front sidemarker light on. I always thought that was the X's way of telling me . . . "I'm gonna need a battery charge buddy!"

No bluetooth either. Nothing fancy in vehicle either. Just a 3.0 with only sport package. Doesn't even have heated seats.