Battery problems

[hollymay]

I've got a 2005 A8 3.0L Diesel....and because I've only been doing relatively short journeys recently on top of the cold weather I had to call out Green Flag the other day when it wouldn't start.

 

They successfully jump started the car.....and then tested it and came up as a 'pass' but only at 53%.

 

Although I've been out a few times since it still seems a bit iffy, particularly first thing and I don't fancy the prospect of being out at work this week and it happening again.....so I went down to Halfords today to ask them to test it again and then hopefully recommend a new one.

 

The guy put it on his tester and it kept coming up with an error sign.....and he said that it was indicating that something was 'taking something out of the battery' despite everything being turned off with the door locked.

 

There are no interior lights on and there's nothing else I can think of that would cause such a problem.

 

Any one got any ideas as to what could be causing the problem....??

[Mark999]

I am having a similar infuriating problem with my 2003 4.2 petrol Quattro A8. It loses enough power over three days of non-use to be unstartable. I fitted a new Audi battery. I have tried removing the fuses which operate the remote door lock sensors (they also cover the door mirror operation) plus the fuse for the instrument lights. This was based on what I'd read elsewhere.  Still the battery drains.  The next thing I thought about trying is the alarm, sited in the engine bay as I understand the batteries can rust and cause a power drain - but this is only guesswork. I have a Ctek intelligent battery charger which I have to use on the car every few days if I'm not driving it much.  It would be impossible to leave this car in an airport car park for even a week as it would be completely dead.

 

I would love to know if there is something I've overlooked that is causing such a substantial drain. My auto-opening boot doesn't work but I can hear the motors clicking and whirring.  I thought about removing the fuse for that to check it, but according to the manual it doesn't have its own fuse, so I presume it must share one with some other function. Anyone know?

I guess it's a question of just trying everything until you find the cause. Do let me know if you do.

[James]

I take it you've tried the obvious of checking for things like interior lights that stay on? It must be quite a slow drain as it doesn't drain overnight then?

[Mark999]

James,

Yes I have checked for 'lights on' even to the extent of putting a video camera in the closed boot to see how long it stays on. I noticed that the tiny lights for some of the controls (not the mains instrument lights) were on at all times, so I pulled the relevant fuse for those. With those and the remote door lock fuses removed the battery went from a fully charged 12.4 volts on Friday to 11.8 volts on Monday with no use or extra charging. The loss is faster than this with the fuses in place, but I'm not certain these are the only draw on the battery. It still starts at 11.8 volts.  I've found the lowest it will go without starting is about 11 volts.

I would like to find the fuse for the self-closing boot motor and rear window demister - both suspects that need to be eliminated from the enquiry. Thanks. Mark

[James]

Sounds like you're doing pretty much all you can then. Careful fuse pulling and testing is often the best way to find a battery drain yourself. Keep us in the loop if you find the cause.

[Mark99]

Hello everyone - I never managed to solve my A8's battery drain problem - an issue I now understand is shared by many other owners it now appears - and reluctantly had to sell it.

A great car spoiled by too much unnecessary complexity and silly electronics which make it less reliable and add weight. 

A missed opportunity for Audi in my opinion.

[Steve Q]

On 9/3/2020 at 10:40 PM, Mark99 said:

Hello everyone - I never managed to solve my A8's battery drain problem - an issue I now understand is shared by many other owners it now appears - and reluctantly had to sell it.

A great car spoiled by too much unnecessary complexity and silly electronics which make it less reliable and add weight. 

A missed opportunity for Audi in my opinion.

Such a shame as the d3 was a beautiful car. Unfortunately all cars are getting to dependent on electrical gadgetary in my opinion. 

[Edward Wall]

Hi, I have had the same problem, I was told when a new battery is fitted it needs coding, never heard of this before, apparently it can be coded using OBD eleven, like I say I've never heard of this but I looked it up and there is information about coding audi batteries on youtube

[ewuschris]

Hi All

firs battery coding its not impotent, secondly have you checked your boot lights? as i had the problem with drain battery, the issue was boot door lock issue, so check the lights in boot or try to take the bulbs of then check if the battery still low. 

[5250]

HI I HAD ALL THESE PROBLEM AND IT A LONG TIME TO FIND.. IF YOU LOCK YOUR CAR AND THE LIGHTS FLASH BUT YOUR ALARM SIRON DOES NOT BEEP.. WHAT IT IS THERE IS A7 VOLT BATTERY INSIDE THE SIRON THAT ROTS AND THEN CAUSES A SHORT AND INTURN CAN FLATTEN YOU BATTERY OVERNIGHT SOMETIMES . I TOOK THE SIRON OFF AND BINNED IT AND HAD NO MORE PROBLEMS.. THE SIRON IS ON THE PASSENGER SIDE UNDER THE BONNET BY THE WINDSREEN MECH RIGHT AT THE BACK ON THE BULK HEAD YOU HAVE TO LOOK FOR IT IT WONT JUMP OUT AT YOU .. MY CAR IS 2004 4.0 A8 TDI SO IF YOURS IS A D3 IT SHOUL BE IN THE SAME PLACE BEST OF LUCK JOHN

[5250]

On 11/16/2020 at 5:31 PM, Edward Lattimer said:

Hi, I have had the same problem, I was told when a new battery is fitted it needs coding, never heard of this before, apparently it can be coded using OBD eleven, like I say I've never heard of this but I looked it up and there is information about coding audi batteries on youtube

 

[5250]

HI ,CHECK THE BATTERY INSIDE YOUR ALARM SIRON THEY ARE 7 VOLT AND LEAK WHICH INTURN CAUSES A SHORT AND FLATTENS YOUR BATTERY.. YOU CAN NO LONGER GET THE BATTERYS SO ITS BUY ANEW SIRON OR OR JUST TAKE IT OFF.. IVE HAD NO MORE BATTERY PROBLEMS SINCE  GOOD LUCK