Power Cell

From Jak and Daxter Wiki

Power Cells are the key power items in Jak and Daxter: The Precursor Legacy. There are a total of 101 Power Cells and if you collect all of them you unlock a Secret Ending. The Power Cells are scattered around the world and gaining them allows your to proceed in your quest, using them to power heat shields, a lifting device and even the Rift Gate. Power Cells are the most important Precursor Artifacts of TPL you can find as stated by Keira. Their true purpose is unknown. It only appears in Jak and Daxter:TPL and very shortly in Jak X.

They, apparently, work like super advanced batteries, with some sort of self-sustaining power source inside them. However, in the New World, they are probably worthless, as 72 Cells for a single Heat Shield isn't efficient. Some of them could also have been taken and destroyed by the Metal Heads. They do still have some advanced power, as they can power a racing vehicle in just a matter of seconds.