The Hidden Entrance is a location in Jak and Daxter: The Precursor Legacy VII. It is found at the end of the perilous trip through the Dark Eco Tube and is an entrance unbeknownst to the commanders of the North Crater Citadel. Oddly enough, although the name of the area is listed as you pass through it, the name is not present on the area list because it apparently contains no Precursor Orbs, Scout Flies or Power Cells.
But 149 total Power Cells is a rather awkward number to have right? There's actually a hidden Power Cell around here.
The Secret Power Cell
As soon as you enter the Northern Crater Citadel, you'll find that the only way to pass a certain challenge ahead is to use a full charge of Blue Eco from a nearby vent. However, the trick is to in fact go back to the Hidden Entrance by lunging to get there faster. In the center of the passage you'll find a Blue Eco platform. You'll just barely make it in time if you're very lucky, and the platform will rise up through a chute in the ceiling, leading to a room with the Power Cell. To get back down, there's a rusty metal platform that you can stomp on. It'll lower you back into the Hidden Passage unharmed.