The 16th Battalion Georgia having been increased to ten companies, it’s designation was changed to 13th Regiment Georgia Cavalry, effective from May 2, 1864

16th Cavalry Battalion was assembled in May, 1862, at Big Shanty, Georgia, and was composed of six companies. It served in East Tennessee and Southwest Virginia and took part in the engagements at Blue Springs, Bean's Station, Cloyd's Mountain, and Marion. In January, 1865, the battalion merged into the 13th Georgia Cavalry Regiment. Lieutenant Colonels F.M. Nix and Samuel J. Winn, and Major Edward Y. Clarke were its commanding officers.
https://www.nps.gov/civilwar/search-battle-units-detail.htm?battleUnitCode=CGA0016BCS

http://ranger95.com/civil_war/georgia/cavalry/13cav_rgt/13th_cav_rgt.html