I changed my battery today. Only had the chance to take it for a short drive but no surge to be seen! Will monitor and report back if I do detect some surge after I have had the chance to drive for a bit longer and in different operating conditions, but initial signs are very good. My battery was definitely on the way out (was reading 11.99V after leaving it overnight) and having been in the car since late 2014 I think it was due a new one.
What brand battery did you install?
A late response but as you can see it’s appearing pretty likely that a new battery resolves this issue, disconnecting won’t fix it, cheers
Awesome, sounding very promising, let us know
I’m scratching my head thinking that my battery (that displays no symptoms of weakness) could be driving this “stop sign behaviour”…
Is there a proper way (VCDS etc) to read battery status and age etc? Why replace it if not truly needed…
Yes, just search for it. If I remember channels 17-19 module 9 I think. I would just buy a charger/charge the battery fully and check if it disappears.
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Glad it’s sorted it out for you hopefully there be no more issues 
Absolutely it makes sense to check the battery first, just confirm load health as well as voltage. But your symptoms sound almost identical to mine, more prevalent when cold because the battery takes a hit when you start the car but that doesn’t mean it won’t happen at other times, with the a/c maybe something similar ? Anyway as we know there’s no certainty with these things.
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Assume you are not in Australia? I just bought it from a local battery specialist shop who home delivered it. Not cheap, was just under AUD$700.
Also agree it makes sense to check the battery health first but with the car’s management systems it might seem the battery has no symptoms but if it is not fully charging then it does start shutting down some systems to preserve starting power. If it is the original battery from a 2013 model I’d say it has provided pretty good value.
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Yes.That will mean at least one of your media, interior then exterior lights will be switched off. In the end the onboard computer will tell you to switch on the engine or it will shut down the electrics.
As you say, I think what points to a bad battery is the lack of any of the above-- also the fact that I have stressed my battery but never got this issue after-- I even updated the software and GPS without connecting a charger 
loads of times working with the car with the ignition on (=headlights on)
I also think very little to be gained from looking at the induced (computed) values, as this is probably pre-mature failure according to the calculations. I believe @Ape_Factory was looking at the chart showing the charging, not sure where that is located. I believe with the regeneration when coasting and the higher voltage, the battery should charge quickly, meaning if the battery is healthy it should not need to charge much when idling.
I am going to dig into the trunk(boot) and uncover that battery, to look for physical evidence of date codes etc, and I will ask my local garage to read into the VCDS settings this week. I did charge overnight, initially at 10amp rate for about 6 hours and then at 2 amp from 11pm onward. Let’s see if today it behaves any differently. It is to be hot today, up to 33c so about 90f. That should keep the AC and fans running and putting electrical load on.
I understand the theory of the vehicle battery management, and how it “protects” the ability to keep reserve for starting, but have not experienced any of that happening to in-car systems shutting. In any case, I will report back with any final resolution activities…
You can go into the VCDS battery module and it’ll give you a “percentage” figure of total battery life as in what sort of overall state/health it’s in, not how much voltage is left. It’s really a guesstimate on the BMS’s part but if you’re having strange issues, always good to start there. It can show you a number of other indicators which can help diagnose a bad battery but a load test is always the best way. Guessing the alternator was probably kicking out fairly high voltage levels on deceleration which necessitated the additional rpm. If you have that, the a/c on, etc…a higher idle may be necessary.
I was logging voltage output from the alternator and its almost all done on deceleration so they can call it regenerative braking. It’s using the alternator drag to help stop the car. Probably worth a gallon per mile.
The trans cooler is obviously a very good idea moving forward. I do have one in stock
And take a look at the Antigravity batteries. For the RS5, the 60Ah H6 or H7 will work best with the BMS. The 40Ah will work but you’ll need to unplug the BMS which takes all of two seconds. If you’re overseas, best to get it from a local distributor or at least check with them. It’s a pain for me to send AG batteries overseas, takes an extra week as I have to send AG a physical check which is just weird. I’ve shipped quite a few to the Middle East at this point as they have no dealer there.
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If it was a lead acid battery, might be a magic eye showing the state on the battery. Not sure the AGM has one. With a weak battery and/or battery saver should be some codes in VCDS.
Actually, and someone correct me if I am wrong, if your battery is taking charge over that long a period of time you mention, I think it is probably in an OK state.
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Well…it could be an old tired battery because after that overnight aggressive effort to charge it, yesterday in the hot afternoon I drove around the local residential area with AC on and the engine just warming up. Could only get two idle “flares” out of maybe 10 stops. [EDIT: so it was better but still not normal] Will go get ECM battery info extracted and I will actually read any labels on the battery.
sounds like the go
Seems that my battery has likely given its best years of service, and would be worthy of replacement. I uncovered the battery topside today and read the BEM CODE label as follows: [EDITED] 8K0915105F and MLA 1304044KBQ, and finally 205 MLA1D44KBQ5. Based on guesses and hearsay on the Internet, this makes me think it was manufactured in 2013 (if “13” indicates the year) or possibly April 2012 if “205” is the code to translate. Can someone educate me here? In any case, it seems I should be shopping for a new battery for this new-to-me vehicle!