Charging keeps going on and off

Replacing the damaged Thunderbolt I/O board solved this problem

Contrary to the zippy teardown iFixit did on this model, the bottom case does not come off the way the earlier models did. It had two inserts that go directly in to recepticals. Trying to slide it horizontally could shear these pins off. It just pulls straight up. When replacing the bottom case, you simply press down on those two spots to click it back in place. I took a couple of photos while doing this repair and will try to remember to post those on a semi-guide. To replace the I/O board you do have to remove the five screws that hold the logic board in place and lift the board slightly to have the room to remove and repave the board. You do not have to take the board out or remove any of the connectors. The board has two P2 screws on the inserts (chrome colored) and two black T5 screws holding the board down.The battery to logic board connector simply slides out horizontally.