I have a 93 850Ci which has had no electrical problems in the four years I have owned the car.  I know the security system puts a pretty high drain on the batteries and I put it on a battery tender when I am not driving it daily. Last week the battery tender would not flip off of charge to tend even after 24+ hours. I tried my other battery tender and got the same result. I had the batteries checked and found a weak left side battery so I replaced them both. i then noticed that the "odometer" light does not shut off when the vehicle has been shut off.  Anyone have  experience with this?