Date registered: Dec 2005
Vehicle: W211 E320 Bluetec R129 SL500 - $1300 car ........ Ford F350 6l
Location: CA Bay Area
Mentioned: 9 Post(s)
Quoted: 1070 Post(s)
Model and year knowledge would really help in pinpointing the advise. If there is fuse panel inside the cabin, you can hook up battery charger on the main rail, or at least 10 amp via radio fuse.
How did you manage to lock keys in the trunk with doors unlocked will really makes me wonder. To my knowledge it is impossible on MB of last 15 years.