Yeah, even if you can charge up the voltage level to a reasonable state of charge, any load is fast dropping it. It seems to simply not be able to store adequate charge anymore for whatever reason. That it's stayed / been kept at a low state of charge for such an extended time, it's probably done for. At leas to the point that you might as well just replace it and start clean.

But that seemed to have already been concluded in the thread and the talk had switched to a replacement battery. There seems to be issue with what battery you actually have in the car. Along with the question about the PR code (if you have your PR codes sticker on hand) and whatever info is on the top of the battery, what part number is programmed in the adaptation value (CAN Gateway, adaptation channel 04)?