Power pack

A power pack is a component of a Transformer that stores fuel.

Fiction

Generation 1 animated continuity

After successfully conquering Cybertron, Galvatron ordered the power packs of several deactivated (but apparently still living) Autobots removed to provide additional fuel for the gigantic rocket engine used to move the planet into Earth orbit. The Rebirth, Part Three

From Teletraan I: The Transformers Wiki, a Wikia wiki.