Audi RS3 Battery Issues: Aux vs Main Power Mystery

Having some experience with electrical systems, I encountered almost identical battery failure symptoms on my 2015 RS7. The power management system showed similar issues, slow starts and unusual electrical malfunctions. After extensive testing, it turned out the auxiliary battery was indeed the culprit causing these car electronics problems. The battery malfunction was affecting the entire electrical system, leading to those frustrating error messages. I took it to a workshop where they performed a complete diagnostic check of the power management system. They confirmed the auxiliary battery had degraded significantly, affecting the engine start reliability. The replacement, including labor and programming, cost me 290 Euro. To help diagnose your specific case, could you share: Current battery age, Exact error codes from the diagnostic scan, Whether the issues occur more frequently after short or long parking periods, If you notice any pattern with the electrical issues (morning, cold weather, etc.) This information would help determine if your RS3 is experiencing the same auxiliary battery issues I encountered and could save you time at the workshop.

Last service was at 12474 KM and the battery malfunction is getting worse. I get the power drain especially after leaving the car parked for 2-3 days. The engine start is particularly weak in the morning. Error codes from the diagnostic scan are P0562 and P0563, indicating system voltage issues. The car electronics started acting up about 2 months ago. Regarding patterns, the voltage drop seems more pronounced in colder conditions. The auxiliary power system warning appears intermittently, usually after short trips. Thanks for sharing your repair experience. The symptoms match mine perfectly, so I will likely proceed with a battery inspection at a workshop.

Thanks for providing those details. After seeing your error codes and symptoms, I am now even more convinced your RS3 is experiencing the exact same auxiliary battery failure I had with my RS7. The P0562/P0563 codes were identical to mine, and the pattern of power management issues matches perfectly. The morning startup problems and increased voltage drop in cold weather are textbook signs of a failing auxiliary battery. The fact that you notice more issues after 2-3 day parking periods also aligns with my experience, the auxiliary power system struggles to maintain proper voltage over extended idle periods. Looking back at my repair, I noticed similar progression: First 2 months: intermittent warnings, Months 2-3: increasing startup issues, Month 4: frequent car electronics malfunctions Given your current symptoms and my experience, I recommend getting it checked soon before the power management system deteriorates further. The 290 Euro I spent on the repair was worth avoiding potential damage to other electrical components. After my battery replacement, all electrical issues resolved completely and normal voltage levels were restored across the system.

Your situation sounds exactly like mine now. The cold morning starts and voltage issues after parking match my experience perfectly, especially with those same P0562 and P0563 error codes showing up. I will schedule a workshop visit this week for a full battery inspection and likely replacement. The 290 Euro cost you mentioned seems reasonable considering the widespread electrical problems I am experiencing. Better to address the auxiliary battery issue now before the power management system gets worse or affects other components. Looking forward to having this resolved and getting rid of those annoying voltage drop warnings and startup problems. The symptoms have definitely gotten more frequent over these past 2 months, particularly after short trips or when leaving the car parked for a few days. Thanks for confirming my suspicions about the auxiliary battery being the root cause. Your repair experience has been really helpful in understanding what I am dealing with.