I own a '98 M Roadster. I took the battery out for winter storage on a trickle charger. Afterwords I closed the trunk lid. Much to my surprise, when I tried to open the trunk lid using the key it would not open. The doors open using the key but not the trunk. Any suggestions on how to open it?
Somewhere under the hood, usually on the right side (passenger side) of the engine bay near the firewall, you should find a plastic, box-like cover about 1.5" x 2" or so, with a large "+" marked on it, a fat cable leading to it and a good-sized bolt underneath it. Nearby there will be a similar, uncovered and unmarked nut/bolt terminal for the ground (negative) connection. Check the owner's manual if you have one, it will probably pinpoint the location in the section on jump-starting the vehicle. The situation you're facing isn't really much different from having a stone-dead battery, so connecting power to these terminals should do the trick.