So when you said "many modern alternators don't actually charge the battery until it falls below a certain voltage," you meant "many modern alternators don't actually charge the battery until a current sensing device sees an imbalance in current draw from the battery?"

:confused: Well it happened to me too after 13 months and 26000km of no problems... High battery drain discharge....appeared this morning.. Car was parked as usual in garage with no key in, and doors were unlocked. I went straight to the dealer and he tested my battery. The results showed 86% of life - Good battery. I looked around and no one has a real solution....

Lets hope this will go away!

First time happened to my 08 X5 yestereday when I started my car. Car was unlocked in my garage. Message shown "High Battery drain" but i can started my car without any problem and message go away when I start the car later again....

No more signs of battery drain and car is actually running better. Of course there was not a sign when it suddenly lost DC power overnite due to fan relay failure.

Update is, got our refund :thumbup: yesterday from BMW for the US$75 fee the towing company charged for using dollies on a locked in park X5. The fee BMW Assist had refused as an extra.

Since I had my issues, I've not left my iphone or my rigged up resistor circuit connected to the electrical outlet of the hitch during extended parks. As such, I've not experienced the issue since.

So I bought the OEM battery charger and tried it only to find it didn't work. When I went to the dealer, they informed me that the alligator clips can not be hooked up to the front of the car but needed to be hooked directly into the battery in the back of the car.

Their advice was the leave the cargo bay open and hook up the battery. There's a brilliant solution and eye pleasing solution.

Quite interesting, since the 2010 Owner's Manual says quite clearly on page 258 to only charge the battery via the terminals in the engine compartment with the engine switched off.

Perhaps you should suggest to the dealer that he should inform BMW NA of the error in the owners manual.

Apparently, the terminals in the front are for a one time boost. For a consistent flow charge, I was told it needs to be hooked to the battery in the back.

Of course, the person at the dealer could have just said that instead of testing the charging unit for defects, which is what I was asking him to do.

:iagree:
The manual states: "Only charge the battery in the vehicle via the terminals in the engine compartment with the engine switched off."

This is how I charge my X5.

That may be, but, as I said, the Owners Manual disagrees with that.