I have a 2004 3.0tdi A6 4F, there is a problem with the battery going flat, what follows is a summary of my problems: I have the above car and it occasionally drains the battery and the car will not start. It has happened twice in the 3 months I have had it. On the first occasion the battery level in the tv display showed 20% charge, but the car carried on working and starting (although interior lights stopped working and keyless entry also stopped), but would not show any extra charge. I then charged the battery with an external charger until it showed full on the charger, but the tv still showed only 20%. I then dug around on some forums and found out about the battery management unit in the boot next to the battery earth terminal (Part No 4F0-910-181-A). The battery has been tested and is fine. I unplugged it, made sure contacts were clean, and re-plugged it in and then I had 70% charge in battery. That seemed to cure it for a while, since then I have had to jump start it twice because the battery has been flat, even though I do 150+ motorway miles most weekdays. I have a third party (not VAG Com) diagnostic kit, which will not even find the unit, the J644 - Battery Regulation (#61). It sees all the other items in the car, and will read and reset fault codes. I have rang local Audi dealer and there is a newer part 4F0-910-181-B, with newer software in it. Looking on forums it seems to be problematic in Audi A6, A8 and VW phaetons, and a change of controller fixes it. I think to controller also needs to be coded to the battery if it is replaced. Audi are quoting £208.72 for the new part. Does anyone have any info regarding this, or a CAN vagcom local to Birmingham that can see if it is my diag gizzmo that is faulty or the battery management unit?