I have this problem to I bought a reman years ago. I tested the wires with a +5v tester seems my charging ribbon is shot. There is a ribbon that connects both batteries to the tablet. 2 red 2 blue 2 black. I ran a cut 5v2.3 amp USB wire directly to the clip on the board. I removed the clip and ran the hoy red from the cut USB wire to the board and the black cut wire to the board and sandwiched it in between the clip. Just to test it. I'm showing 96% battery life now I checked through twrp. I believe I ran the hot on the constant red wire which thinks its got full battery. But it's not charging I believe I need two run the hoy directly to the blue wires for the battery to charge.