Ahl's Battery, Delaware Heavy Artillery (Union)
United States    U.S. Military
   U.S. Military    Delaware
   Delaware    Delaware Military
   Delaware Military    Delaware in the Civil War
   Delaware in the Civil War    Ahl's Battery, Delaware Heavy Artillery
   Ahl's Battery, Delaware Heavy Artillery 
Brief History
Ahl's Battery was organized at Fort Delaware July 27, 1863. It mustered out July 25, 1865.
The Wikipedia article for Ahl's Battery has more information and sources.
Companies in this Regiment with the Counties of Origin
Men often enlisted in a company recruited in the counties where they lived though not always. After many battles, companies might be combined because so many men were killed or wounded. However if you are unsure which company your ancestor was in, try the company recruited in his county first.