Usually you can find some deep holes that have some type of odd metric screw at the bottom. It may be a specialty screwhead you may not have the proper bits for. If you cannot remove those or if there are none, look for a seam where it looks like the case was put together. You may need to use a hacksaw to slice it just enough to cut away the welded or glued seam. Try poking around with a paint scraper or thin flat screwdriver to see if there are any retaining clips to push in to separate the case. Use caution to not damage the batteries inside and be careful that sharp objects don't slip and jab you. It may just take brute force to crack one open and then worry about gluing it back together again. Good luck.