Car battery drain

[Edtwozeronine]

Often make specific forums are a good place to find answers to this sort of problem, if it's a common problem it will have cropped up on an Audi Forum.

 

[ruston]

If the noise is coming from the back of the engine the relay could well be in the nearside windscreen motor well.
In some Audi models some electrics are housed there.
A common problem was that access required damaging the water seal of the trim of the wiper grill and allowed water ingress into the fuel pump relay , this caused erratic fuel pump problems and eventually failure of the relay, causing the car not to start or erratic running.
This may not apply to your model , but may be a similar issue.
As has been said a visit to an Audi site may be prudent, and this problem alone would not drain your battery in 30 minutes.
Some Audi fuel pumps had a switched negative on cranking.

 

[static zap]

30 mins is fast for a fully charged battery.
(For rattling clicking noises as it flattens ,could still be a red herring ,due to dropping voltage.)
Fresh charged battery , attached to a cold car ,see if anything warms in 10 mins -- (not very professional ) but saves £80 on DC ammeter-probe. (no experience of your model ,but thinking a cooling fan / chunky resilliant wiper motor ,or alternator --Any long forgotten in boot audio gear/alarms)..may feel warm / smell toasty .

 

[James]

Your local car spares shop will have a battery tester.
It is basically a large resistor and a volt meter combined.

When they put it on the battery terminals it shows the condition of the battery when it is under load.
Maybe asking them to check the battery would be a good first step.

Alternatively if you have a volt meter, you could with a fully charged battery, disconnect it from the car, put a known load I.e. a light bulb on the battery as a load and check the voltage every 5 min.
I suspect that before half hour is up the voltage will be well below 12v signifying a battery that is well past its sell by date.