... you have one of the relatively small number of A8 Battery ECUs installed in late 2004, early 2005. There are a number of indicated problems, published in an Audi TIB, that are apparently fixed with the ECU update.
NOTE: This info. published by the author based on his own experiences.
From what I've seen of all the A8 VCDS Autoscans, there seems to be at least five variations of the ECU 61 Battery Manager ECU Part and Hxx level.
There is no software update of the ECU code required if the VCDS log for ECU is any of the three variations below:
Part No SW: 4E0 910 181 HW: 4E0 915 181
Component: ENERGIEMANAGER H02 xxxx [where xxxx is 0240 or below]
Part No SW: 4E0 910 181 B HW: 4E0 915 181
Component: ENERGIEMANAGER H02 0240
Part No SW: 4E0 910 181 C HW: 4E0 915 181 C
Component: J0644 BEM H12 0550
If it looks like variation 4 though, with H11 level as in my case, there is a software update - but it needs the appropriate CD [4E0 906 961 G] and VAS 505x!
Part No SW: 4E0 910 181 C HW: 4E0 915 181 C
Component: J0644 BEM H11 xxxx [will be above 240 and below 510]
The update takes the software level in the ECU from whatever level is there [mine was 0390] to level 0510, as below.
Part No SW: 4E0 910 181 C HW: 4E0 915 181 C
Component: J0644 BEM H11 0510
Regards - Julian