I purchased this vehicle Certified Pre-Owned 3 months ago. Since then, I have had 3 instances where the battery was completely dead when I went to start the car. After the 3rd instance I requested that BMW replace the battery. 2 days ago, I awoke to find that all the lights on the car were on. They were not on when I went to bed at midnite the previous nite. Also, I left the headlamp knob in the 0 position, i.e. automatic. The battery was nearly dead: the car had lost the date and time setting and I had a series of warning messages, however it did start up. The only culprit I can think of is that the electrical system is somehow shorting due to water. In 2 of the instances, I had washed the car the prior day and drove it back in the garage.

Has anyone had a similar experience or does anyone know is this is in the realm of possibility?