Regenerative phasers were a type of phaser weapon developed by Starfleet in the 24th century. The TR-116 rifle project was abandoned in favor of regenerative phasers. (DS9 episode: "Field of Fire") In the year 2381, regenerative phasers were used against the Borg at the Battle of Acamar during the Borg invasion. The regenerative phasers failed, a fact later relayed to Admiral Elizabeth Shelby by Captain Holly Hostetler Richman. (ST - Destiny novel: Mere Mortals)