Help Please Battery draining

[adyRE]

Hi everyone,

Background: I had a battery replaced but it turned out to be the incorrect battery and kept draining. So I got the battery replaced for a factory reccomended battery and had it coded to the Ecu as reccomended. Battery was fine for a few months but I have noticed again that the car is struggling to start and has on occasion not started at all due to the battery draining to 11.4vdc. Before this new battery I had the car checked for drains etc and the autoelectric place said there were no issues or drains etc.

I still think my battery is draining and I have no idea why or where from. I've checked the alternator which is charging the battery at 14.3vdc. There's no obvious issues or warnings on the display. I even changed the glow plugs thinking they may be faulty.

It's a 2011 A4 tdi. If any has any ideas it would be greatly appreciated. Thanks

 

[Dippy]

Drains can be intermittent. I had one on my B5 S4. The only way to diagnose is by removing fuses one-by-one and measuring current from the battery, taking account of the idle/sleep states that some equipment have. In my case it was the audio system which would intermittently stay in an idle state and not enter the low current sleep state. This was enough to drain my battery over about a week so that it wouldn't start. Unless an autoelectrician does a thorough investigation, issues like that can be missed.

 

[rum4mo]

I spent off and on about 18 months chasing a battery drain in my older daughter's late 2009 SEAT Ibiza 1.4 16V SC, she was away in KL teaching so that car was not really needed much. From my investigations I established that everything was okay so it must have been a BCM S/W issue which was known about by VW Group - my the first SEAT main dealer ignored my thoughts and reading on the internet that this could be a possibility, so they replaced a "faulty" steering sensor - no change!! Luckily or unfortunately that dealership closed down so after more months of monitoring the drain, I did that by fitting a long monitoring lead from the battery to outside the front of the car, so I could log the voltage daily and work out when to intervene and recharge, and so save the battery. I then went to the next closest SEAT main dealership and told them what had been done so far, the service adviser took on board what I said and immediately said that they had had this issue with a similar aged Polo them had taken in as a trade in, and so they submitted a technical support report to SEAT mothership - that worked and new S/W sorted that out.

I would suspect that if you hand this into an Audi main dealer, the first thing they will do is to check for any system failures, after that and maybe repairing any found faults, they should connect equipment to that car and monitor the drain current over night or more. I'm not suggesting that your car has a S/W issue that is keeping it awake or re-awaking the controllers that have been sent to sleep to save drains, I'm just making you aware of the trouble that some draining problems can come from. How/why my older daughter's late 2009 Ibiza took about 7 years (bought by her new) to display this issue might have been down to an aging battery and a lower rate of usage - I chased that problem to death, many people get sick of their car and just sell them on.

 

[audiwaterpump]

you'll have to start unplugging fuses to narrow it down.

 

[adyRE]

Still having issues and tonight after the car had not died for 3.5 weeks this happened??? Please have a look at the video and if anyone has any ideas I'm all ears. Thanks

 

[bhodgkiss]

Might have been mentioned already, but simply get your multimeter and put it on voltage mode (mV) and put contacts across each fuse in turn
Make sure car has powered down for 15 mins first
This will then tell you what’s drawing current!
Depending on the size of the fuse, you can then get a good estimate of the current draw from the mV value from the lookup table here:

https://us.autologic.com/news/testing-parasitic-draw-via-fuse-voltage-drop

Any more than say 70mA total draw (across all fuses) and something isn’t right.

For example a 30A fuse showing 1.6mV is 985mA which is almost a 1A draw....very big. That will drain a half charged battery in under 2 days

Very easy to check

 

[audiwaterpump]

Might have been mentioned already, but simply get your multimeter and put it on voltage mode (mV) and put contacts across each fuse in turn
Make sure car has powered down for 15 mins first
This will then tell you what’s drawing current!
Depending on the size of the fuse, you can then get a good estimate of the current draw from the mV value from the lookup table here:

https://us.autologic.com/news/testing-parasitic-draw-via-fuse-voltage-drop

Any more than say 70mA total draw (across all fuses) and something isn’t right.

For example a 30A fuse showing 1.6mV is 985mA which is almost a 1A draw....very big. That will drain a half charged battery in under 2 days

Very easy to check

Good advice there.

Also, if you camera has infra-red capabilities then a photo of the fuses will instantly reveal which one is drawing power.
Speeds things up a bit.

@adyRE has the car been modified in any way, or have any aftermarket add-ons?