If you have his Regiment and service dates, which is likely, then you can find online histories of that Regiment Including the battles they fought in. Add in your ancestors service dates and that should tell you where he fought. Another excellent source is his Civil War Pension application and records which you can order online. I have a number of Civil War Ancestors and ordered their records. You find out interesting stuff, like one of mine was docked for a screwdriver when he mustered out.He was at Gettysburg and Franlin that I know of ,diary states this.Plus he was good at taking prisoners.Was almost taken prisoner too,someone he served with saved him from that shooting the soldier in the back.The 2 that were killed,Both were killed at the battle of Antetiam.One took a bullet to the head and other shot in the chest.Both were not good soldiers.I have been to gettysburg,this was 2 years ago