The Power Cell is a type of ammunition in Serious Sam: Next Encounter.
The Power Cell is a cube that looks very similar to the Serious Sam 1 version of Electricity, but with a non-transparent inside and darker blues on it. When picked up, it gives the player 50 units of Power Cell ammo.
Power Cells are somewhat common after the Sirian Power Gun is picked up. This lets the player use the Power Gun for an extended period of time throughout a level.