Audi Q4 e tron Battery Issues Plague Owners

Had a similar situation with my 2021 Audi Q4 e tron last winter. Having some experience with electric vehicles, I recognized the symptoms immediately as auxiliary battery related. The warning messages and electrical gremlins started showing up out of nowhere, especially after the car sat unused for a few days. The power management system was clearly struggling, showing various error messages on startup. Took it to a certified workshop where they diagnosed a failing 12V auxiliary battery. These batteries handle all the basic electronics while the main high-voltage battery powers the drivetrain. The auxiliary battery replacement plus diagnosis came to 290 Euro. Important to note that battery malfunction symptoms in EVs can be tricky to diagnose without proper testing equipment. Car electronics are heavily dependent on stable power supply from both batteries. Could you share: How old is your auxiliary battery? Do the issues occur more after the car sits unused? Are you seeing any specific error codes? Does the main battery still charge normally? This information would help determine if your situation matches what I experienced with the auxiliary battery system.

Last service was at 84385km and the voltage drop issues started shortly after. Can confirm the problems get worse after the car sits unused for 2-3 days. The main high-voltage battery charges fine, but the auxiliary power system shows intermittent failure messages. The error codes point to low voltage in the 12V system. Engine start sequences are becoming increasingly unreliable, especially in colder conditions. Looking at the diagnostic report, the auxiliary battery is still original from 2023, which seems early for complete failure. Recent voltage tests show inconsistent readings, fluctuating between 11.2V and 12.4V. Would getting a higher capacity replacement battery help prevent future car electronics issues?

Thanks for those details, especially the voltage readings. Having gone through this exact scenario with my Q4 e tron, those voltage fluctuations match what I experienced before my auxiliary battery failure. While 11.2V to 12.4V might seem acceptable, a healthy auxiliary battery should maintain a more stable voltage around 12.6V. The voltage drop you're seeing, especially after sitting idle, is a clear indicator of declining battery health. The original battery failing this early isnt typical, but the high-tech systems in these EVs put significant strain on the auxiliary battery. My battery failure happened at similar mileage, and the voltage readings were nearly identical before replacement. Based on my experience, a standard capacity replacement battery is sufficient, no need for higher capacity. The key is ensuring proper integration with the power management system. After my battery replacement, all electrical issues and error messages resolved completely. A quick voltage test right after a battery failure message appears will usually show readings below 11V, confirming the auxiliary battery as the culprit. Given your symptoms match mine exactly, Id say youre dealing with the same auxiliary battery issue I had.

Based on your recommendation and shared experience, I will schedule a service appointment to replace the auxiliary battery. The matching voltage readings and similar symptoms you described make me confident this is indeed a battery failure issue rather than a more complex electrical problem. The low voltage pattern showing up after idle periods and the inconsistent startup behavior align perfectly with what you encountered. Knowing that a standard replacement battery resolved all issues in your case is reassuring. Will skip considering a higher capacity battery since its not necessary. Getting those error messages with a 2023 vehicle is frustrating, but at least battery replacement is a straightforward fix. My voltage drop readings between 11.2V and 12.4V clearly indicate auxiliary battery deterioration, matching your experience exactly. Will report back after service to confirm if replacing the auxiliary battery resolves all the car electronics warnings and power management problems. The battery failure symptoms match too precisely to be coincidental. Thanks for helping diagnose this through your detailed voltage testing experience.