Power Cores, also known as Energy Stones, were small bricks filled with large amounts of energy that were used in the Split Mountain Era of Exo-Force to power all but the smallest of Battle Machines. It was also said that Power Cores contained data, though this was only shown once in the Exo-Force promo, inside a downed Fire Vulture.
Power cores provided energy to a battle machine's primary weapon through a cable. Theoretically, if this cable is broken, it will cause the power core to overload on itself and short circuit, or even explode if enough energy is built up in the cable. This tactic is shown both by Takeshi during a training exercise, and by Hikaru during a battle with a Fire Vulture, however, in both cases it only disabled the enemy battle machines, and it is unknown if the cores overloaded afterwards.