I dont know if there is a secondary fuse, but if you found a fuse that had a label saying it was for the cig. lighter, I think that would be the only one. As far as I know, the cig. lighter in modern cars (including the Aspires) only is on when the ignition is on. So with the ignition off - the cig. lighter has no power to it.
For any car that I like to take on trips, I always add another 12 volt accessory socket, that is on full time. It means the bother of mounting the thing, running a wire from it to a fuse that I put near the battery. But it lets us charge the cell phone, operate the GPS and the CD player whether the ignition is on or not.