The Citizen Navihawk wrist watch is a high quality watch with a unique movement technology termed "Ecodrive" by its manufacturer. The power cell requires replacement approximately every three years. Replacing the power cell requires that the back of the watch be removed. Unlike many powered watches, the Navihawk back does not simply lift off, but requires a specialised watch-back removal tool.
Locate the slots along the outer edge of the removable case back. There are six of them.
Set the pins on the watch-back removal tool according to the tool's manufacturer's instructions (see resource list) to match the slots on the outer edge of the Navihawk back.
Insert the pins of the case-opening tool into the slots on the edge of the back.
Push down gently but firmly and rotate the case back counter-clockwise. The back is threaded into the case much like a large bolt would be. When the back loosens, continue turning the back counter-clockwise until it is free of the case.