Hi guys! Had the same problem when I just bought my C180 1994 Euro version early this year. The battery in the rear boot was venting acid and gas out of the tube and through the hole in the floor under the spare. The tube was ruptured and the stuff spewed around the back and rusted up the steel in the weaker joints and scratched spots which have been fixed now. Got the electrics checked and it was ok and a new battery was installed and it runs very well now. Only use the car once a week and it is still almost fully charged.