You need to check the area surrounding the battery connector for possible pry damage. There are two square MOSFET’s (see blue highlights in the picture below) that communicate the charge status to the CPU. If they are damaged or missing, this could cause the symptoms you see.
[image|1987245]
Look for anything else that could be problematic, like damaged flexes etc. You could always try going bare board to eliminate as many variables as possible. Otherwise, it is possible that the charge circuit was damaged (Tigris/Tristar).