The Battle in question was The Battle of Glendale (Frayser's Farm), and my family members (there were a few) fought for the Confederates. According to letters we have, he was Company F and H, Second South Carolina Rifles, Moore's Rifles. The family member in question died storming a battery of artillery on a hill, he died of a minnie ball to the head.
Could I get the name of your relative in question? If you don't want to post on here, please PM me.
Does this part of your family come from Pickens County, South Carolina? Many of the members from Company F and H hailed from here. Company F, along with companies A through E, were formed in October to November 1861, and were originally attached to the 5th South Carolina Battalion Rifles.
Company H was formed on April 27, 1862, shortly before the Seven Days battles, when the 2nd Regiment South Carolina Rifles was officially organized. Companies H, K, and L were added to complete the new regiment. These companies used the 5th South Carolina Battalion Rifles, your relative's original chain of command I'm assuming, as its nucleus.
So it stands to reason that your relative mustered in Company F, and was transferred to Company H when it stood up.
The newly formed regiment, during the battles of Gaines Mill and Frayser's Farm, sustained 149 casualties. These were the only battles that they were engaged in during the Seven Days.
I found a first hand account from Lt. Augustus Dean, an officer in Company G, who served in the regiment. And even though he wasn't in either of your relative's specific company's, I believe his memoir can provide the insights you're looking for. He writes before commencing the Seven Days Battles that regiment consisted of:
We were fresh troops and had not had any hard service so we were kept either on picket or near the picket line nearly all of the time till the Seven Days battles started June 25.
The regiment didn't have the best living arraignments, no surprise for a Civil War soldier:
Our company stayed at some old houses a good deal. One of them had fallen down but the boards were still on it. Some the others and I would crawl under it when it rained to keep out the rain, though we generally got wet. There were seven or eight dead horses within seventy or a hundred yards of where we stayed, that were killed in the battle of Seven Pines. We had to endure the stench while we were there. We used water out of a well that was right by the road and which had no cover over it. It was so full we could dip the water with a cup. When it rained muddy water from the road ran into the well.
He writes a detailed account of the regiment's first taste of combat at Gaines Mill, and proceeds to detail the day's engagement at Frayser's Farm.
On Sunday morning, June 29, 1862, we marched back up the river for some distance, crossed and went back to our camp near Richmond. We did not stop but turned down in the direction of Malvern Hill. On Monday evening we were in the battle of Frasier’s Farm. We formed in line of battle along a fence with a house in front of us and a patch around the house.
Here's the link if you'd like to read the rest of it in full detail. It's about 1/8th down the page.
The 2nd Regiment South Carolina Rifles had an impressive record of battles. They were in second Manassas, marched with R.E. Lee up to Maryland, before getting pushed back down to Fredericksburg, and through the Wilderness campaign. They would ultimately serve all the way through the end of the Civil War, and surrender their arms with the remnants of Lee's Army of N. Virginia at Appomattox Courthouse.