-( 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
One of the Power Cells in Misty Island requires you to use the Zoomer located around the rear of the island (I say rear, but really, the island loops, so just go around the left side of the island to reach the Zoomer pad faster). Zooming across the water, you will see several Lurker zeppelins rising and falling. You need to run into the Lurkers and avoid the bombs on the front and back of the zeppelins. Defeat all of them to make a Power Cell appear in the boat nearby (and don't forget to get all of the Precursor Orbs on the water as well!)