As a companion to Fox’s Fighting 300, a list of “fighting” infantry and cavalry regiments in the Union armies, this site also features “Distinguished Batteries” to honor the “fighting” light artillery units.
The light artillery was composed of batteries with a maximum strength of 150 men and six guns; before the war ended many of these units were reorganized as four-gun batteries. (This was already happening at the time of Gettysburg as can be seen from the unit strengths and losses for some of the units.)
To qualify as a fighting battery, a unit had to lose at least 15 men and/or officers killed in action or needed to be singled out for distinction by Fox.
A list of the Army of the Potomac’s “Distinguished Batteries” present at Gettysburg is available here. These units are also denoted with a special graphic on their respective monument pages.