I woke up this morning to a completely dead battery. I bought the car new, it was delivered 1/31/18. The dealer was insinuating that my wife killed the battery by leaving the ignition in the on position which seems impossible to me since the wife shuts it off by using the start stop button and we found the car with mirrors folded and doors locked indicating she locked it last night. Merc showed up at the house with a new battery and asked to have the car brought in to re set everything (whatever that means).Then they told my wife that they were going to do a diagnostic search and they will get to the truth again looking at my wife with an accusing expression. After some investigating the service advisor explained that there is a drain on the battery that shouldn't be there and they need time to diagnose the issue. They gave the wife a loaner and said they would call. Apparently the drain on the battery goes back to before delivery because when the salesman tried to start the car while it was on the showroom floor it also was completely dead at that time and was immediately put on a battery charger. Has anyone else experienced this problem and if so please provide the solution.