-( Story related, cannot be missed )-
*While this is "flagged" as possibly story related, the real note is that... you could scrape by without having all 101 Power Cells early on. It would be in your best interest to avoid back-tracking at the end to get this for the final ending. I would advise doing this as soon as possible, as the Blue Eco vents help out, so the sooner the better, as Blue Eco aids in the collection process.
Level: Misty Island
While retracing your steps through this treacherous area in search of Power Cells, you will come to an open arena sealed off by Precursor Doors. Once you step in, you will face waves of Lurkers attempting to overwhelm you. Both the normal kind of Lurkers and the skull-armor Lurkers will come down from the rafters. Thankfully, they also drop some Red Eco. If you find any, scoop it up and spin to clear out several Lurkers around you. Once you floor the last bit, some steps will appear leading you up to the Dark Eco well that Daxter first fell in during the intro. Avoid that, and go around it to get the Power Cell above it.