There are 5 Power Cells that can be found in the game, but for some of them you need to make a progress in the story first. However, you could complete the entire game and then return to these locations to obtain them all, but by then you might not need them anymore. Here are all five locations where you can find them.
Power Cell 1
During “The Womb of the Mountain” quest, your character wakes up in the mountains in the All Mother area. There is a side room on your right that you can get to by crouching and moving through the hole in the wall. You will find the power cell inside.
Power Cell 2
The second power cell can be found during “The Maker’s End” quest in the area by the same name. There is a huge tower nearby that you can’t miss. At its very top, on the 12th floor, you will find the second power cell.
Power Cell 3
The third power cell is a part of “The Grave-Hoard” quest, so there is no chance you won’t see it. You will stumble upon it once you open the door locked by a ring puzzle. The power cell will be right behind it.
Power Cell 4
The fourth power cell is in the GAIA Prime area that you visit during “The Mountain That Fell” quest. As you progress through the story, you will find yourself on the third floor of a building and need to go outside in order to rappel down. Before doing that, however, go left by the rocks and you will see a power cell in the purple-marked area.
Power Cell 5
The Ruins area from the prologue can be accessed later on, as you free roam the map. Use your spear to forcefully open one of its doors and you’ll find the last power cell in the bottom right of the map. It will be in the purple area.These power cells serve a unique purpose. Once you’ve collected them all, you need to take them to the Ancient Armory bunker and insert them. You will get both the amazing Shield-Weaver armor and, obviously, “Got The Shield-Weaver Outfit” trophy.