Ancient capacitor
From The Stargate Omnipedia
Ancient device similar to technology inside Stargates, designed to collect power at a high energy and regulate output at a manageable frequency. Such a device is useful in preventing a dangerous overload of energy-sensitive equipment.
KEY EPISODE
Line in the Sand - Colonel Carter rigs an Ancient capacitor between naquadah reactors in order to more evenly regulate power into Merlin's computer.