Jim, the owner of that 2007 S550 should call for help when he has a problem because apparently he knows nothing about cars, or at least MB automobiles. In the picture of the failed battery the positive terminal is clearly marked with a "+". How do you hook up a booster pack backwards? I suspect the booster pack has visible warning labels about the correct cable orientation.

Good luck sorting out that problem. If I were you I would have the car towed to the nearest MB dealer, and have the owner bite the bullet. Consider it an expensive "learning experience".

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Fred Hoelzle