I've had my 3 since last August and have never had this problem. Over the last couple days I kept randomly seeing a red flash coming from my cluster. This morning was quite a bit cooler than it has been for about 2 weeks. I hit my brakes for a stoplight and my battery light came on for about 3 seconds and then turned off when I had come to a stop. I have nothing aftermarket draining the battery. I went around my block again just to see if it was a fluke and sure enough it came on every time that I hit the brake. The car has less than 20k on it and still has the factory battery. Any ideas?