Hood locked - fuse box unlocking method doesn't work?!?

[lurky]

Hi
I removed the battery from my boxster 2007 and put it in the garage for the winter.
I left hood unlocked but someone must have pressed it down and locked it.
Today I hooked up a jumper cable to an suv, ran it to the porsche, connected it to the red fuse and black to auto frame, and tried to open the hood with the button. The cable is connected and I try the buttons and nothing happens.

But now I'm thinking, is the electrical connection with the battery necessary to complete the circuit to unlock the hood? In most cases, there would be a battery there, even if is dead. Am I correct that the battery needs to be there to unlock hood via fusebox? If so, how do I open hood now? Thanks