In September 1864, the recruits and reenlisted men of the 3rd Massachusetts Battery were consolidated with the 5th Massachusetts Battery. On October 3, those of the 5th Massachusetts Battery who had served out their term and did not reenlist went home. A total of 39 of the original members did reenlist for a second term of three years so that, with the addition of some new recruits, the battery continued to serve. They operated at various points along the Petersburg siege lines but for the most part the battery was stationed at Fort Hays to the south of Petersburg. During the final assault on Petersburg on April 1 and 2, 1865, a detachment operating two guns of the battery took Confederate Battery 27 on the siege lines. This engagement was the last time the battery fired their guns in battle. When the Confederates abandoned Petersburg, the battery was withdrawn to City Point, Virginia and remained there until May 3. On that day the unit began its return to Massachusetts, marching to Washington to turn in their guns and equipment. They reached Boston on June 3 and were mustered out at Camp Meigs on June 12, 1865.