I was incorrect in the dates of his furlough.
His companies muster roll for Jan/Feb 1864, dated March 5, 1864 records him as Present.
The next muster roll is for the period Feb. 29 to Aug 31, where he is recorded Present with the notation "Absent on 30 days furlough from April 7 to May 6, 1864."
I checked his units Record of Events found in the Supplement to the Official Records, Ser. 82, Records of Events which are found starting on p. 550 under "Record of Events for Snead's Battery, Virginia Light Artillery (Fluvanna Artillery), September 1862-October 1864:
February 7.--They were ordered to Morton's Ford on the Rapidan River. After two days' marching, very severe on men and horses, they arrived to find the enemy had retreated, when they were ordered to erect quarters and stables again near the Plank Road, about four miles east of Orange Court-House, which is their present location.
The next entry is:
Stationed at Bunker Hill, Berkeley County, West Virginia, [March 1]-August 31, 1864.
When last mustered this company was stationed at Louisa, Orange County, Virginia.
April 23--They were ordered on picket at Somerville Ford, where they remained.
Later, they were engaged at Wilderness, Spotsylvania Court-House, near Bethesda Church
Thereafter they participated in Jubal Early's Shenandoah campaign starting at Lynchburg.
September 28 -- Marched to Waynesborough
They were last recorded at New Market October 20.
I also found Nelson's Battalion was also known at 31st Battalion Virginia Artillery. Ser. 85, p. 427.