The birth year of your ancestor Harbert Cooley, according to the census records of 1850 and 1860, was approximately 1806-1808, therefore, at the beginning of the war his age was approximately 53-55. He was born about 10 years earlier than you thought.

(He was the husband of Esther, who was also born in South Carolina at approximately the same time as he, 1807-1808.)

Best regards--