I get it towed to my shop, Valley Motorwerks and explain everything to them. (They've got one mechanic who really knows E9X's) After examining the battery he tells me what he thinks happened; It turns out when you change the battery in an E9X, you have to plug in a diagnostic tool and punch in a code telling the car that you are putting in a new battery. (I changed the battery myself a few months ago and put in an interstate) Furthermore, according to him you can only use a BMW OEM battery in an E9X. By failing to do either, this is what will result.
Can you tell us EXACTLY please what code of battery (size) and amperage rating was sold to you?