This is yet another excellent example of unit sources existing in abundance that aren't readily evident to the public. Even if no one has written a history of this battery, there can still be much about it in print.
Here's one example that will provide more information and description than most people will care to read -- two volumes titled The Long Arm of Lee or, the History of the Artillery of the Army of Northern Virginia by Jennings Cropper Wise. The original set published in 1915 has a fairly recent reprint, so it's available.
The index includes twenty references to this battery. If we include references to the artillery battalion in which this battery served, there are many more. For instance, volume II carries several passages about Milledge's Georgia Battery during the Shenandoah Valley Campaign of 1864.