A6 Battery Drain while standing

[ianjgillis]

I live in France and own a 3 litre TDI A6 Quattro (Oct 2005).
In May 2008 I bought a new Navigation DVD and had the car software reprogrammed to make the TMC traffic info work.
In July 2008 I found the battery drained after three weeks of not being used and the battery state display had disappeared. Audi agent replaced battery and the power management box GVF 4F0 915 181B.
Since then the battery state display can degrade to 10% in 10 days or so and if the weather is cold in 5 or 6 days.
Since I have a smaller car for shopping the Audi gets used for less frequent long journeys, so it can be sitting in the garage for up to a fortnight, but when used it has a good run of at least 100km.
Recently I did one such run on a Monday; by the following Friday the battery state was down to 10%; the car did start reluctantly but the internal lighting etc was shut off by the energy management system.
I have put an AVO meter in series with the battery to measure the quiescent current. This starts at about 5.5 Amps and progressively steps down as the onboard computery shuts down, ending up at 150 mA.
I've just left it with the Audi dealer who kept it for three days and ran the diagnostics on charge rate etc and can find nothing wrong with it. He blames lack of use (total mileage is about 8000 km since July 2008). I say the long journeys should ensure a full battery, he says low total mileage reduces battery capacity.
I am very fond of the car but I can't trust it to start when required any more. Please has anyone else had similar problems and how did they overcome them?
regards,
Ian

[ezhik]

I can't answer your question directly, but would be interested to know how long you owned the car before May 2008 and if you had the same issues before then.

Generally speaking I would agree with your comments, longer journeys ensure a fully charged battery, low usage should not result in low battery life unless it is becoming too discharged regularly. On the other hand 5.5 Amps is too much when the car is standing, ignition off, (how long is taking this much current for ?). As a comparison mine has stood for 4 weeks when I've been away and started as if it was fully charged. I would expect it to stand for a couple of months without problem.

I also do low mileage, in the winter I use the lights on short journeys, demister fan etc, but never have a battery problem or symptoms of poor charge.

If its only taking 150mA there is probably no fault with the cars electronics, are you sure the replacement battery is a good one? Is it being properly charged, ie alternator problem?

[Peter D]

The 5.5 amps is OK until it all shuts down. 150 ma is high. Disconnect the alternator and measure it again this could be a leaky diode in the rectifier pack thus not charging propperly and leaking of when off. Regards Peter

[ianjgillis]

I can't answer your question directly, but would be interested to know how long you owned the car before May 2008 and if you had the same issues before then.

Generally speaking I would agree with your comments, longer journeys ensure a fully charged battery, low usage should not result in low battery life unless it is becoming too discharged regularly. On the other hand 5.5 Amps is too much when the car is standing, ignition off, (how long is taking this much current for ?). As a comparison mine has stood for 4 weeks when I've been away and started as if it was fully charged. I would expect it to stand for a couple of months without problem.

I also do low mileage, in the winter I use the lights on short journeys, demister fan etc, but never have a battery problem or symptoms of poor charge.

If its only taking 150mA there is probably no fault with the cars electronics, are you sure the replacement battery is a good one? Is it being properly charged, ie alternator problem?

Hi ezhic,
Thanks for your reply!
I bought the car in March 2007. I had no such problems before the reprogramming for the new navigation DVD.
I understand and accept that maintaining all the on-board systems as they power down needs quite a lot of current. The 5.5 Amps lasts only a few moments; the 150 mA takes perhaps half an hour to reach if locked, longer if not locked by the key button (I had previously, erroneously, assumed that leaving the vehicle unlocked in a secure garage would be less of a drain without the immobiliser activated, but this is obviously not so).
The garage assure me that they have done the normal tests of charge rate and discharge potential of the battery, so no, I'm not absolutely sure that the replacement battery is good!
However I kept the old one, so I could try substitution...
It's not easy keeping on top of these things, even with half-decent French!
regards,
Ian

[Peter D]

OK I sort of missed that. It's time to pull the DVD Nav fuse and see if it is the culprit. Did you have a NAV before or did they add the GPS amplifier. ? Regards Peter

[ianjgillis]

OK I sort of missed that. It's time to pull the DVD Nav fuse and see if it is the culprit. Did you have a NAV before or did they app the GPS amplifier. ? Regards Peter

Hi Peter D,
I had a nav system before, but the traffic report TMC system wasn't functional. The new DVD provided that functionality, but it crashes a couple of times, which is when I found that there was a software update applicable to late 2005 Nav systems to add the TMC functionality.
I don't understand your phrase "did they app the GPS amplifier".
I should say that I'm a retired electronic engineer and am computer literate but have no more knowledge of the Audi systems than my pussycat does!
regards,
ian

[JimC64]

Hi Guys,
I've had exactly the same problem. Had the car for around 19 months now and used to do decent mileage ( maybe 700 - 1000 a week ) but don't anymore. In fact now it can stand for a day or so ( that IMO is not long ) especially in this cold weather and it really struggles to start.
I've had to call out the AA around 11 months in cos it would NOT start, trip to garage and new battery replaced under warranty??
Around 3 months ago the car would not start again!!!!
The AA guy said he thought the problem may have been " fuel run back " as the car was parked on a very very slight upwards slope - I've parked Mondeos on this same slope for years and they started first time every time.......what a load of croc!!
Anyways, now I'm getting to the point where its really starting to struggle to start unless very very frequent usage........sorry guys, sumthins deffo not right here!

Keep ya posted

Jim

[Peter D]

Sorry typo. 'did they add the GPS amplifier.' It does not sound like they added any additional hardware. Audi must have a quiescent current figure for your model and build. 'Crasher' may be along to through some light on this. Regards Peter

[solo284]

I had battery drain that turned out to be a faulty starter motor, which once replaced cured the problem.

[ianjgillis]

Sorry typo. 'did they add the GPS amplifier.' It does not sound like they added any additional hardware. Audi must have a quiescent current figure for your model and build. 'Crasher' may be along to through some light on this. Regards Peter

Hi Peter,
The energy management box (don't know the name in English) was replaced (368 euro). I take it "Crasher" is the group electrical guru? I'd like to know if 150 mA is a typical figure for quiescent current with vehicle locked. Interestingly it was 410 mA for some hours with the vehicle unlocked but key out, but eventually settled down to 150 mA. To fully drain a 110 Ah battery should take over 30 days at that rate.
regards,
Ian