Antti

Weird thing happened to me today.

I drove my -05 A6 3.0 TDI Avant to my garage, left it there with doors unlocked but all doors closed. And then 20 hours later when we were suppose to go somewhere, my wife comes complaining to me that the tailgate won't open. I went to look and realize that the battery is almost empty, inside lights are really dim and when I turned on the ignition I hear this constant clicking sound from a relay of some sort, instrument leds are flickerin.

Because we had to leave I disconnected the ground from the battery to prevent further drain. (lucky we have our trusty Volvo that doesn't fail on us :-), When we came back I charged the battery with a 4A charger for few hours, connected it back and managed to start the car.

The MMI battery level indicator showed 10%, I let the car idle for almost an hour to reach 100%. Then I drove it back to carage and connected the charger again and I will let it charge overnight. Lets see how it acts tomorrow, I have to call the Audi dealer on monday.

Has this happened to anyone else? What could have caused this?

One thing also came to my mind, when I reversed the car to the carage, before the battery went dead, when I turned the ignition off I heard the handbrake motors running for a second or two even if I didn't engage the handbrake. It has done that couple of times before, just as I shut off the car, so I thought that maybe it's normal routine to keep the motors clean, anyone else noticed this on their car? or could it be my handbrake which is acting up and eating up the juice out of my battery?

April

Also, the car will usually charge must faster if you take it for a drive.

Antti

The car is driven atleast 40km of highway + all other hobbies, So I don't think it's caused by lack of charge, and no signs of weak battery were shown before I left it in the garage. And it only spent there 20 hours, I would understand if it were standing there for two weeks.

And because it charged so quicly afterwards when I got the car running. As I said it idled only about an hour and then already the MMI-showed 100% for the battery. (Couldn't go for a ride because I had had a couple of glasses of red wine :-) I measured the voltage when the car was running and it was around 14 volts.

I charged the battery yesterday, now it's been standing in the garage for ~10 hours and I checked it this morning and now the MMI shows 100%

So something drained the battery during that night. Well I hope the Audi dealer has an explanation.

I searched the archives and found a similar thing happened to NightBlue4.2 last year:<ul><li><a href="https://forums.audiworld.com/c6a6/msgs/2766.phtml">https://forums.audiworld.com/c6a6/msgs/2766.phtml</a</li></ul>

April

Sounds like an intermittant short. How annoying.

Antti

This morning the battery was empty again.
Well on the other hand it should be easier to debug if it's not that intermittant, I'm taking it in today. I phoned the service today, they suspected that maybe the battery is busted?? well anyway they are taking a look at it tomorrow.

Calcio

Let us know what happens. My Jetta is in the shop again after having a dead battery twice after getting a new battery two months ago. I suspect that it is the battery.

Antti

I just got a message from the service that the car is OK (I'm a little bit skeptic though :-)

I called the service and they said they saw from the powercontrol module log history that on June 24 59Ah was drawn from the battery so some device was left on by the powercontrol module.

They updated the software on the module and were confident that it should correct the problem.

I'm impressed about the detail they get from the diagnostics!

I just hope that this software update fixes the problem. It seems cars are more and more like computers nowadays, patching, patching... :-)

Antti

Well the software update didn't help, after a week when I left my car stand still one day the battery was dead again. I took off the fuse from the hitch electric module that was installed a month ago and that stopped the draining. Talked to the service rep and he said he has seen the same thing before.
If some device on the CAN-bus does not go to sleep mode, and keeps sending data to the bus, it will keep all nodes awake and that drains the battery. I will install the original Audi hitch electric module, and hope that it's better quality.