There is quite a bit of information on Graves Battery at the 1st Kentucky Brigade website.
http://www.rootsweb.com/~orphanhm/index.html

It was originally known as the Issaquena Miss Battery recruited and outfited by Seldon Spencer.
http://www.rootsweb.com/~orphanhm/spencer.htm

There doesn't seem to be any record of Graves Battery after Chickamauga, the site where thier most famous casualty occured. Major Rice Graves was killed in combat at Chickamauga and I believe some of the members of the battery were merged with Cobb's Battery when Robert Cobb took over command of the artillery battalion. I have 22 men listed on both rosters. I don't know what happened to Seldon Spencer who was commanding Graves Battery at Chickamauga.