Used to be the batteries in a lot of European cars were under the back seat, or in the trunk. The cells needed to be vented to the outside to prevent buildup of hydrogen gas as well as spattering of Corrosive Electrolyte (Sulphuric Acid. Some still do this. MB does not. With the newer maintainance free batteries this is not a problem. Hey, we've really had some battery testing weather around hear lately. Really cold weather can be a great diagnostic environment for a lot of systems in your car. Happy motoring.