A power pack is a power storage unit that can be used to power devices of various kinds.
In 2265, the crew of the USS Enterprise (NCC-1701) considered adapting the power packs used at lithium cracking station on Delta Vega for use on their engines. (TOS: "Where No Man Has Gone Before")
Phaser power packs, used in some type-2 phasers and phaser rifles, were one of the most common types. In the 23rd century, members of a landing party when carrying type-2 phasers would also carry one or more "reserve" power packs. These packs were designed to be quickly "swapped out" to "reload" the phaser.
- Phaser power packs (or cells) have been seen in episodes of Star Trek: Enterprise, Star Trek: The Original Series, Star Trek V: The Final Frontier, and Star Trek: Deep Space Nine.
Another type was typically used as an emergency power source onboard starships for use when main power was off-line. They could be used, among other things, to "unlock" closed doors. (TNG: "Starship Mine")
A third "power pack" is a component of the aquashuttle that is required for operation of the vessel's phasers. In 2269, the power pack was damaged when the aquashuttle carrying members of the USS Enterprise crew was attacked by a sur-snake during a mission on the planet Argo. (TAS: "The Ambergris Element")
Vedala ground vehicles were operated by power packs, which can be easily consumed when the vehicle uses full power for long durations. (TAS: "The Jihad")
When investigating a deralict Promellian battle cruiser, an Enterprise away team used a power pack to power the Bridge's functions. (TNG: "Booby Trap")