S3 (52 plate) Current Drain

[S3Robin]

I have had an Audi S3 (52 plate) since new but since moving to the Isle Of Man have started to experience problems with a periodic flat battery if I leave the car for 2 weeks or so without driving it. It is fair to say that the longest journey I do over here is only about 30 minutes duration so the battery doesn't get the charging time that it used to in the UK, but nobody else seems to be experiencing this problem over here. I have had the car into several garages who can find no fault. The battery was replaced a few months but now I have the same problem again. I tried checking the current draw on each fuse to see if I could detect any obvious problem. Some circuits registered a small current but this is to be expected to run the electronics in standby, alarm etc.

Has anyone else experienced anything similar or can give me any advice as to what current I should expect to see drawn on each circuit, for comparison purposes.

The fuse circuits which registered non-zero currents with the car standing idle were as follows:

(fuse#)

12 - Onboard diagnosis, reading lights, alarm 355mA (all lights off when meas. taken)

15 - Instrument Cluster, Central locking 10mA

16 - Magnetic Clutch / Water Pump 128 micro amps

17 - Heated door locks 55 micro amps

28 - Fuel pump 1.2mA

30 - Sunroof 48mA

32 - Engine Management 0.5mA

37 - Radio 4mA

48 - Luggage Compartment 38mA

Cheers,

Robin

Edited September 4, 2008 by S3Robin

[craigyb]

355mA is a 1/3 of an amp, that will drain a battery easily enough.

[PetrolDave]

(fuse#)

12 - Onboard diagnosis, reading lights, alarm 355mA (all lights off when meas. taken)

That's about 20 times what it should be.

Have you checked for fault codes with VAG-COM?

[S3Robin]

Dave,

I suspect that measuring the current drawn by each fuse was not the best approach and that I should have started by measuring the total battery current. To measure each fuse requires having the driver's door open and then holding-in the door-close sensor and locking the car to arm the alarm etc. The car is currently with an auto electrician who can find no fault and reckons the current drain is normal. I think VAG COM may be next port of call. I don't have one at present but there seem to be plenty on Ebay (cable and basic fault code reading software) for about £15. I noted another post on here where the alarm circuit was causing the battery to drain. The problem is there are no Audi dealers on the island so no real expertise.

Thanks for the advice.

Cheers, R

[PetrolDave]

The car is currently with an auto electrician who can find no fault and reckons the current drain is normal.

What does he say the current drain is? If his figure is also in the region of 350mA then there is no way that is normal.

[Tame Technician]

Instrument pack. Drain should go away when fuse 15 removed.

Common as muck.

[PetrolDave]

Instrument pack.

If the instrument pack takes 350mA then it's cream cracked - that sort of current drain will flatten a car battery in a few hours never mind days.

[Tame Technician]

Thats what I mean, the Instrument pack in F**k*d and causing the drain. I've done loads for that fault. Removing the fuse will show for sure. Make sure it is fuse 15 though, i was just going by the description posted. Could be a different fuse for the combi- processor inside the pack itself.

[S3Robin]

Okay, I am now about £200 worse off through various so called mechanics 'having a go' and finding nothing but the problem still remains. One even had the cheek to tell me that the problem was that I am not driving it often enough and thay any car left for 2 weeks will get a flat battery (!). I do however have some fault codes which seem to suggest that I may have been on the right lines with my original diagnosis.

Fault codes are:

0991 - Cabin Light Short with Power

01134 - Alarm Horn - H12 No Communication, Intermittent

Last time the battery went flat the fault code pointed to the central locking (he didn't tell me the eaxct code); he cleared the fault code and it hasn't come back so this may have been caused by the battery cycling (?)

I don't know what fuses these faults relate to. DTC 0991 sounds like maybe fuse 12? If anyone has had any experience of these fault codes and which fuses they relate to, my next step is to charge the battery, remove this fuse and see if goes flat again. Grateful for any tips or advice.

Cheers,

R

[Tame Technician]

The most important thing when testing for battery drain, is to do so when the car is "asleep" at the top of your post you have detailed amps in circuits, but this will most likely have been tested with the door open an you at the fuse box. i.e not asleep.

By asleep I mean all the modules have powered down, the sign that the majority of then have is when the hazard light switch stops glowing, but complete such down is 20 mins or so after that.

When I test cars at work I open all the doors bonnet and boot, but then latch and the latches so the car thinks every thing is closed. You can check by turning the ignition on and making sure you dont have any warnings on the dash. Then leave the car for a full hour to go to sleep.

Then you need an ameter inline at the battery earth. I use and inductive one that goes round the outside of the cable, buy a normal one will do and is actually more acurate. If using a normal ameter, You have to take great care not to blow up your amerter here. With the ignition on or similar the current pull will be over 10amps and nuke your meter.

My advise is disconnet the battery earth put a jump lead between the earth cable and the battery and wiring in your meter here too. Only when the car has been left to go to sleep remove the jump lead and all the current goes through the meter. This will show you very acuratly how many amps being drained, at this point remove fuses one by one until the drain drops then you have found the circuit with the fault, then you need to look at whats on that circuit that might be causing the problem. Dont open doors or turn the ignition on until you have finished and reconnected the battery properly or have the jump lead in there, or you will blow up your ameter.

This is the normal procudure for checking drain on most vehicles (certainly your S3), and what your mechanics should have done.

I'd still bet its the dash on an A3. Common as muck. But at £500 or so do check it out first.

If you have any question dont hesitate to ask. I dont think any of the fault codes are relevant by the way.

[S3Robin]

Thanks for all your help and tips. I have had another go at this but this time with the ammeter connected in series with the battery. The trick was to leave the car to go to sleep (good tip!). I saw that the diagnostics module (fuse 12) took about 10 mins to fully go to sleep the first time after reconnecting the battery (a bit quicker for subsequent locks / unlocks). After locking the car and allowing the interior light delay to switch off the current dropped to about 340mA (mainly the diagnostics module) but then after the diagnostics module powered down the current dropped to between 40-60mA which sounds pretty normal. I checked the equivalent 'sleep' current on my partner's Nissan Micra (which always starts even if left for weeks) and that was 90mA, so I am reasonably confident that this is okay (60mA @ 12V is only 0.7 watts so tiny really). I am therefore still none the wiser as to why the battery is draining. The only 2 conclusions I could come up with were that either battery is faulty or that the problem is intermittent.

I have since had the battery tested and confirmed it to be faulty, but to be honest, given the number of times it has gone flat it is not possible to determine whether the battery had a manufacturing defect originally or has effectively been destroyed but all the deep cycle discharges. The only way I will I find out is to replace the battery and see if the new one starts to go flat or not. Which leads me on to my next connundrum.....

Given that the vehicle sometimes doesn't get driven for a few weeks if I am away, I wanted to fit a higher capacity battery to it this time to extend the duration I could leave it before it went flat. Checking out the various battery manufacturer and reseller web sites the best battery technology appears to be AGM. The last battery was a Motaquip '065' type (242x175x175mm LxDxH) 55Ah, however the higher capacity batteries (70Ah+) are mostly only available the slightly larger size of 278x175x190mm ('096' type). The connundrum is that most of the battery supplier / reseller web sites provide a 'vehicle look up' facility to allow you the find the size of battery compatible with your vehicle. The majority state that Audi S3 2002 model requires a 278x175x190mm ('096') battery. However, having measured the plastic casing that houses the battery it only measures about 263x175x190mm (LxDxH). I wondered if the casing sides were expandable but can't see a way of doing of this. So how come they reckon a 278mm battery is going to fit inside a 265mm casing ? Since I can no longer drive the car to a garage to get advice and will most likely have to order in a high-capacity battery as they are not generally stocked here in the IOM, I would appreciate your advice and experience on maximum size battery that can be accommodatd in an Audi S3 (8L model, BAM engine code) and if the answer is 278x175x190mm, how the battey casing can be expanded to accommodate it? I have scoured the user handbook, and ElsaWin workshop manual but can find no information on this, nor anything on the internet other the conflicting information given on the battery suppliers / resellers web sites.

Looking at a posting by Sponge (http://www.tyresmoke.net/forum/audi-a4-s4-cabrio/114945-battery-dimensions.html ) it looks like the casing is movable on an A4 S-line, but don't know if the same applies for an S3?

Thanks in advance for your suggestions !

Edited January 11, 2009 by S3Robin

[shark_90]

Is it possible for you to use a maintenance charger like the CTEK 3600?

[S3Robin]

That would be an ideal solution if the car was garaged but unfortunately I live in a flat and the car is parked on the public road. I have an Accumate Pro charger (AccuMate Pro 12V & 24V high power AccuMate) which I bought recently (intelligent charger similar to the CTEK) which I can use as a top-up when I visit my folks, but the existing battery was too far gone (some cells already short circuit and battery down to 10.75V) to be recovered so I need a new one anyway.