fly along the left wall thing and you should c a big boulder blocking the way. shoot it
with the yellow eco and go throught there and thats how you get it. hope this helps! :)

go in spider cave get eco and run ou fast as u can. shoot bok on ledge and pcell pops out

then follow the wall intill you see a boulder blocking the way to somewhere {the power
cell}
shoot at it intill it explodes then follow the path and it should take you to the power
cell ^.^

Before you enter the 'cave' towards the end, there are lots of trees and a blocked
(yellow)Eco vent. Near this there is a bolder which obstructs the Powercell. You need to
go past it and continue to Volcanic Crater, then to snowy mountain and unblock the yellow
Eco vents. Then go back and shoot that darn bolder,and the Powercell is yours! :D

hope this helps, from Australian Jak and Daxter fan.