Neuroelectric power cell
A neuroelectric power cell was a type of power cell used by Borg drones. 

While studying the corpse of a Borg drone recovered from a disabled cube in 2373, The Doctor inadvertently activated the drone's backup neuroelectric power cell when he used a cortical probe on the drone's axonal amplifier. The power cell triggered an autonomic response which seemingly brought the drone back to life. Although The Doctor managed to deactivate the drone, B'Elanna Torres discovered that the Borg's original programming had been reset. ()
Borg components