So i Found the solution for my Xperia Z3 Compact Battery Problem, staying Battery level at exact 50 Percent no charging. Thing happened to me after LCD Repair. Please watch out the Battery cable and Battery connector on the logic board. I t seems to be that you can connect the battery at the wrong position on the connector. after releasing them again and cleaning both parts i watched very closely that cable connector of battery and socket on logic board fit together. Now i heard the familiar click ! and voila, with a new start battery was at 9 % and charging. Its a bit tricky to connect properly because you hardly see both parts. Hope this information helps you.