MB didnt really mean for that connection to be used for JUMP starting BUT for charging the battery.
No matter what you SHOULD remove the rear seat & open the windows while charging. These batterys can "gas" when charging & IF the battery vent hose isn't connected you can have problems.
Also the original batterys aren't sealed, you need to add water at times.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)