Audi a8 d3 4e.... Battery draining problem

**bg7788** · 04-11-2012,11:45 AM

Hi guys, I have AUDI A8 D3 4E chassiss with battery draining problem. I have changed the battery as advised as the original one was already 6 years old so...but the problem still exist. I dont know much about recoding the battery or anything and I been told by the garage the new battery was recoded to the car(I dont think they did that anyway) but even if they recoded I dont think this is my main problem. I have find out that: after parking the car after use if I do not open the boot or any doors except the driver door then the battery does not drain that quick overnight and I still have power in the next few mornings in the cold weather(summer days is much better), but after turn off the car after use and then open the boot or any of the other doors for example to take the shoping bags out and then lock the car, just after a couple of hours I may have only power to start the car(turning very slow anyway) and "low battery" beep and indicates in my central display. I am just guessing now if I have really problems with the central locking or doors and boot or the problem makes my battery drain is totaly different from above. I have read most of the forums around but everyone have a different isues with the battery I believe and to be honest I really dont want to guess, just want some one to help looking at my car. Would appreciate your responds guys. Many thanks

**audi_130bhp** · 04-11-2012,12:13 PM

It seems like the battery was not coded to the car, i had the same problem few years ago. You need a vcds and instructions how to code are on the ross tech website.

**bg7788** · 04-11-2012,12:29 PM

Thanks for the replay audi_130bhp. The problem draining the battery is from 2 years(new battery changed one month ago),wasnt that bad 2 years ago at the begging but with the time been becomes worst and worst, now I may have a battery for a week or most of the cases now just for a couple of hours to maximum a day. I haven't vcds but have the instruction how to recoded the battery(no point without vcds anyway

). Do you know some one who can look at my car? Also two of my keyless buttons on two door handles does not lock the car, its unlock it when you pull the handle but just dont want to lock it when pressed the buttons on top. Many Thanks

**EG-4.0TDI** · 04-11-2012,06:22 PM

Hmm... Interesting one this.

If I'm reading correctly, the battery drain is very fast.

(1) By way of background:

You don't say what the engine in the car is but I would guess the that battery is something like 80-100 amp hours. In theory therefore, a 1amp drain would take 80-100 hours to kill the battery (simplifying things a little here). A battery should normally last about four months which means the sleeping drain on the car should be about 0.02-0.04 amps.

When you lock the car, it goes to sleep after about 15 minutes and all systems shut down (if you look in the dark, you can tell when it has fully shut down because the hazard light switch on the dash will stop being illuminated - it remains illuminated whilst the gateway is still active).

Killing a fully charged battery in 'a day' would mean an ongoing drain of about 4 amps (ie 4 amps per hour times 24 hours = 100 amp hours) - about the same as leaving the side lights on.

Killing a fully charged battery in 'a couple of hours' would mean an ongoing drain of 40-50 amps which is a huge drain. That would be the equivalent of leaving the headlights and full beam lights on.

(2) So to your situation

So therefore the question in respect of your car is 'what is failing to shut down once you lock the car and that is pulling around 4-5 amps?'

Given you seem to be having trouble with the keyless door handles as well I would strongly suspect that the issues are related. If these aren't working properly, there is a good chance that they are keeping the gateway awake by continuing to communicate when they should be asleep. Which would, of course, cause the battery to drain.

I'd recommend having a look in the manual under 'fuses' and find the numbers of the ones relating to the keyless entry system. Then go to the fuse box (drivers side, on the end of the dashboard facing the door there is a panel that you can remove by inserting a flat blade screwdriver) and pull the relevant fuses out. Then see if it solves the drain.

If it solves the drain, you know broadly where the issue is but will then need to get someone to diagnose which part of the keyless entry system is fried using a diagnostic machine (VAGcom or other) which probably means a visit to a dealer/independent. On the bright side, you will at least be able to start it to get it there!

**snapdragon** · 04-11-2012,06:53 PM

I too have started having spurious battery drains and I tool am having handle problems on a door.
As said by EG4.0TDI, maybe the system is seeing handle actions but no key nearby so nothing is seen to happen, but it is keeping it awake.
Also I have found in the past that once the battery goes flat, it's best to charge it from a mains charger and then code for a new battery using the serial number increment method*, otherwise it never seems to fully recover.

*In VCDS, just change the battery serial number by a digit, Recode, and then change it back if you like and recode again.
This resets all conditions, SOC and status fields.

**bg7788** · 05-11-2012,08:33 PM

Hi EG4.0TDI, thank you for your respond to my problem. Let me start with...the car is 3.0TDI with "bosch 110amp battery fitted". I have checked today in the fuses on both side driver and passanger but can not locate a fuse related to the keyless entry, do you KNOW which is the one I need to remove please?
Also just to add something important which I forgot to mention on the first post.... when I am right to the car and try to lock the car, the car is locking it and just after 1 or 2 seconds the car unlock its self(does not matter if I lock it with the key or pressing the button on the handle) but if I am just say 3-4 metres away from the car and lock it with the remote key then the car does not unlock its self unless in the next 1 minute I get closer to the driver side only then the car unlock its self again.

.....

**a8 tech** · 05-11-2012,08:58 PM

without a scan i can offer no advice

a8 battery manager holds all the critical data required to localise the issue

kessy (keyless entry) seems to be a problem but thats specultion

a door showing open will pull around 4 amp

**somerandomguy** · 29-12-2012,11:53 PM

Originally Posted by bg7788

Hi EG4.0TDI, thank you for your respond to my problem. Let me start with...the car is 3.0TDI with "bosch 110amp battery fitted". I have checked today in the fuses on both side driver and passanger but can not locate a fuse related to the keyless entry, do you KNOW which is the one I need to remove please?
Also just to add something important which I forgot to mention on the first post.... when I am right to the car and try to lock the car, the car is locking it and just after 1 or 2 seconds the car unlock its self(does not matter if I lock it with the key or pressing the button on the handle) but if I am just say 3-4 metres away from the car and lock it with the remote key then the car does not unlock its self unless in the next 1 minute I get closer to the driver side only then the car unlock its self again.

.....

I dont know if this is still a problem, but is exactly what happened to mine. You need to work out which handle is triggereing the unlock by moving the key towards the front and rear on each side immediately after locking the car. In my case it was the rear passenger.
the fault seems to be that the touch sensor is permananly detecting touch and so keeps the ECU awake, and immediately unlocks the car if the key is in range. The only fix is to change the handle.

**south105323** · 03-12-2012,08:34 AM

Alarm siren is on top right of engine bay. Unclip the rubber gasket, lift the panel up and you will see the siren. My NiMH batteries had leaked, the alarm was going off intermittently. Have a new one to fit in the next day or two.

**mckenna** · 03-12-2012,02:49 PM

Thanks I found the siren and cut it open.
As expected, the batteries had leaked all over the circuit board and power connector. I tried wiring in another battery pack but the siren is dead. The connector is also damaged, it looks burnt and parts of it are crumbling away. I think there was some significant leakage current going into this, which would have added to the background battery drain.
It looks like a new siren is needed, maybe a new one, as a second hand one could have the same problem, unless they improved the design. Later parts have an "A" suffix, and are a different shape.

The other issue I had with the keyless entry control box antennas was fixed by changing 2 MOSFETs as described elswhere in this forum.
Static current readings from the Battery regulator are now 0.01A, so I think (fingers crossed) the battery drain problem is fixed.

Thanks to all on this forum - a great source of information!