I can't answer for others individual situations but in my case the battery had a few completely dead cells and was creating some kind of dead short (so i was told) so putting power to the fuse box didn't do anything....hence the need to use the other method of opening the hood. This wasn't the first time I've had a flat battery on a Porsche and previously i was able to use the fuse box method successfully....but not on this occasion. The trick is if you are parking your car up for prolonged periods use the Porsche cig lighter adaptor trickle charger. It can save the battery and all sorts of grief.

 

When you completely discharge the battery, odds are good that you will also damage one or more cells as the products of sulfidation fall to the bottom of the battery, act as a conductor, and cause a short between adjacent cells. A completely discharged battery at first acts like a big resistor when current is applied and absorbs all of the available current, leaving none to operate the electrical solenoid on the hood lock.

Try leaving the alternate power source hooked up via the fuse box connector for at least five minutes before giving up on it, giving all the little electrons on the battery a chance to line up properly and reduce draw. If it doesn't work after that time, you are indeed f**ked and need to find that release cable under the wheel well.

 

it might be a good idea for posters to watch how to remove the front bumper for cleaning the crap from between your radiators and condensers and along the way you will find the wire that releases the trunk should you ever get a flat battery again. I found mine but before replacing the bumper I sliced a one inch cut with a Stanley knife in the air scoop on the passenger side next to the air temperature sensor and pushed the loop end of the pull wire through it so I could reach it easily. I was showing someone today how it worked and it still does with the slightest of tugs.
Here is the video

 

A follow up to my last message. You may need to feel around for the release wire. You can see where it is connected to the center of the release mechanism and trace it back to the loop. Mine simply fell out in front of me as I worked. At first I didn't know what it was . Then I figured it out and cut the slot in the air scoop. BTW I also found a broken Police radar scanner which I disconnected and taped the wire up. Even though the video shows two guys removing the bumper. It doesn't weigh more than a pound and so easy a child could lift it. Well good luck. It's a job that kills two birds with one stone. You find how to get into your trunk with a flat battery on board plus your engine runs at a lower temperature owing to clean radiators.

 

Agreed 100% - Did it a few weeks ago.

 

I remove my battery when storing the car and lock all the doors and close the front and rear lid. When it is time to connect the battery I just use the key to unlock the door, hook up a booster pack to the fuse box and the ground and pop the latch open. If it works with no battery I would also assume it would work no matter what state the battery is in. I'm no expert though.

 

Please confirm if this was with battery connected or removed, thanks. My situation is the battery is disconnected/removed from my 997 and wandering if connecting external battery to fuse box will open my lid.

 

Look up at my post. Also confirmed by Alcyon.

 

FWIW, with an almost-completely dead battery -- 3.7V -- I connected a battery charger to the fusebox trunk lid terminal and to the door latch, and as soon as I plugged in the charger the trunk lid unlatched with no key fob involvement. Before encountering this thread and dashing out to buy a charger, I had pulled up on the latch release under the driver door, so maybe that armed something?