Audi RS6 Battery Alarm System Fault, Fix Guide

Had a very similar auxiliary battery issue on my 2017 Audi RS7 last winter. As someone with moderate experience working on Audis, I first noticed the battery alarm acting up, followed by complete system failure. The workshop ran a system diagnosis which confirmed the auxiliary battery was severely degraded. These backup batteries typically last 4-5 years, and when they fail, they can trigger multiple error codes related to the battery signal and alarm system. The fix involved: Complete battery system diagnosis, Replacement of the auxiliary battery, Reset of the alarm system, Recoding of the central electronics Total cost was 330 Euro for parts and labor. Since the repair, no more battery alarm issues or system faults. Would need to know: Exact build month/year of your RS6, Current mileage, When did the battery problem first appear, Any other electrical issues noticed, Whether regular battery is also original This would help determine if your issue matches what I experienced and if the solution would be similar.

Thanks for the input. Had my last service done at 149000 KM, just 1500 KM ago. The battery problem started shortly after, with similar symptoms to what you described. Our cases sound quite alike given both have auxiliary battery and alarm system faults. The car battery check I did shows the main battery is still good, which narrows it down to the auxiliary system. The battery signal issues started appearing more frequently during cold starts. Will schedule the repair soon and report back with the results, hopefully the fix is as straightforward as in your case with just replacing the auxiliary battery.

Thanks for the update. The symptoms you describe match exactly what I experienced, especially the cold start battery signal issues. In my case, the auxiliary battery was the root cause of the alarm system failure. Since your main battery tested good during the battery check, this further confirms my suspicion that the electrical issue stems from the auxiliary unit. The timing after your service could be coincidental, as these backup batteries tend to fail around the 4-5 year mark regardless of maintenance. My repair experience suggests you are on the right track. The fix should be relatively straightforward since there is no car battery problem beyond the auxiliary unit. Make sure the workshop performs a complete system reset after replacement to clear any stored error codes. Worth noting that in my case, they found slight corrosion on the auxiliary battery terminals during replacement. Ask them to check and clean the connections while they are at it, this helps prevent future electrical issues with the alarm system. Looking forward to hearing if the repair resolves your issues. The 330 Euro cost reference I mentioned earlier should still be fairly accurate for the complete job.

Thanks everyone for the detailed responses. Just wanted to close the loop on my battery alarm situation. You were right, it was indeed the auxiliary battery causing all the trouble. The workshop confirmed the battery signal issues were directly linked to a failing auxiliary unit. The electrical issue diagnosis matched exactly what was suggested here. Total repair came to 310 Euro, which included: New auxiliary battery, Complete battery system reset, Terminal cleaning, Alarm system recoding After the fix, all battery problem indicators cleared up and the alarm system is working perfectly again. The cold start issues are completely gone too. Will definitely keep an eye on the battery check readings going forward to catch any potential problems early. Really appreciate the help in narrowing down the cause. Having the cost estimate beforehand also helped set proper expectations for the repair.