mishar

Or all of them are half dead.

There is a link in another ongoing tread to Audi PDF and they say that battery should be at least 12.5 in order to begin software update. That pretty much supports theory.

mishar

There is another thing. To check real voltage we should disconnect battery. Voltage is dropping with load and A8 is always doing something in background.

awdinut

I want to find out if the overnight consumption I my A8 is having which leaves my battery at 12.2V is excessive or par for a D3. I have acertained that the battery is good.

mishar

I measured voltage again this morning and it is 12.17V. That's basically same since it is colder this morning in my garage. My battery is Odyssey (made in US) and it is 3.5 years old. I don't think it is in a really perfect condition.

05SilverA8

I measured mine and it was 12.13 after sitting for a day and a half. Car started fine. After running for a few minutes it was up to 12.5V with car off. I am watching the battery. After a week sitting it was down to 10% on the battery monitor screen in the MMI. I know I only have a few weeks/month left on my battery, it is 6.5 years old.

s4master1

12v is perfectly fine for an idle battery, is the amperage what matters at start up.
if the battery reads below 12.6v when the car is running it will cause the control units to lose the adaptation values ie: driving habits that govern shifting patterns, throttle response.
as the car sits the control units go to sleep mode and only draining 24 to 28 milli amps from the battery, any healthy battery can handle that for up to 5 days.
the starting control unit or on older cars the X circuit keeps the power away from all the accessories and control units not necessary at start up and giving all the amperage to the starter and injection ignition systems, you notice how the headlights go out when you cranking the engine and all the accessories (windows,a/c,sunroof and a lot of other energy consumers don't work during cranking.