[PaulE]

If you have a battery tender with a cigarette lighter adapter you could try that and see if you get a different result than you did with the fuse box terminal.

Otherwise, if you can jack up the passenger side of the car using the jacking point behind the front tire, and remove the front wheel, you can then remove the inner fender liner and you'll find an emergency release cable taped to the bottom of the headlight tray. Remove the tape and pull the cable loop, it will open the front hood. Sometimes owners of Boxsters relocate this cable so that it is accessible from the tow hook socket behind the cap in the front bumper. You can pry off the tow hook cap in the cover and see if a previous owner of your car happened to do this.

You'll need a decent 19mm six point socket and a breaker bar to get the lugnuts off the wheel, since your lug wrench is probably locked in the trunk.

That's all I've got, good luck and let us know what happens.