Sifakis, Compendium of the Confederate Armies - South Carolina & Georgia, page 161 gives the following:

13th GA Cav Regt organized by the addition of 3 Co's of the 16th GA Cav Bn 1/16/1865 [to date from 5/2/1864] per SO#12, Adjutant & IG's Office - disbanded by Brig Gen John Echols, Cmmdr, Dept of SW VA & E. TN, at Christianburg, VA 4/12/1865
FIELD OFFICER: Samuel J. Winn, Lt Col
ASSIGNMENT: Vaughn's Cav Brigade, Dept of SW VA & E TN - Jan-Apr 1865
BATTLE: Waynesborough - 3/2/65

16th GA Cav Bn - aka 16th Partisan Rangers Battalion - organized with 7 Co's in summer 1862 - increased to Regt & designated 13th Cav Regt as above
FIRST COMMANDER: F. M. Nix, Lt Col