A week ago, the steering wheel locked and the braking system and airbags and cameras malfunctioned. We took it for service at BMW. They said the battery caused the malfunction. On thanksgiving day, we were going around 25-30miles per hour when we slammed on the breaks and the breaks didnot function and we could not stop the car. The automatic emergency breaks never activated. We lost power of braking and brakes locked and we impacted a car in front of us with damages to our car and the other vehicle.