Audi A5 Electrical Nightmare: Battery May Be Culprit

I had almost identical issues with my 2015 Audi A4 last winter, which matches your symptoms. As someone with some car maintenance experience, I initially thought it was just a dead battery, but the problem turned out to be more specific. The workshop diagnosed a faulty battery sensor, which was causing incorrect readings and leading to battery drain issues. The sensor was misreporting the battery state, triggering multiple error codes and causing the electrical system to behave erratically. They replaced the sensor and recalibrated the system, costing 315 Euro in total. Since the fix, all electrical issues disappeared and the vehicle battery has been performing normally. No more flickering lights or starting problems. To provide more specific advice for your case, could you share: Current battery age, Exact error codes stored, Whether issues occur more when engine is cold or warm, If you notice the problems getting worse over time, Battery voltage readings if you have them This information would help determine if your A5 is facing the same battery sensor issue or potentially something different in the electrical system.

Latest service was at 110000 KM, about 2 months ago. The battery terminals were actually cleaned during that service. My multimeter shows 12.1V when the car is off, which seems quite low for a car battery. The issues definitely get worse in cold weather and have been gradually increasing over the last few weeks. I noticed the battery warning light came on briefly last week. These symptoms match what others described before a complete battery failure. Im still waiting on the workshop but wanted to check if this voltage reading alone confirms a discharged battery situation. At 111267 KM, this would be the original battery from 2017, so age could be a factor too. Would appreciate insight on whether I can still drive it to the workshop or if I should call roadside assistance to avoid getting stranded with a dead battery.

Based on your voltage reading of 12.1V, you are definitely dealing with a heavily discharged battery situation. This matches exactly what I experienced before getting stranded with my A4. A healthy battery should show around 12.6V when the car is off. Given this is your original battery from 2017, you are well beyond the typical 4-5 year lifespan. The cold weather is likely the final stressor exposing the weak battery condition. While the battery terminals were cleaned recently, this only addresses contact issues, not the internal battery capacity which degrades over time. I would strongly advise against driving it to the workshop. When my battery was at similar voltage levels, it failed completely without warning. Better to use roadside assistance and avoid the risk of being stranded, especially since cold weather will put extra strain on an already weak battery. For reference, after my battery failure incident, I learned to monitor voltage regularly: 12.6V+ : Healthy, 12.2-12.4V : Partially discharged, 12.1V or below : Critical, risk of failure A new battery plus installation will likely cost around 200-300 Euro, but prices vary between suppliers and battery types.

Thanks for the detailed information about voltage readings and battery condition. Your advice matches what my mechanic told me, better safe than sorry with these battery issues. Will call roadside assistance today rather than risk getting stranded. The cold weather lately probably explains why everything got worse so quickly. Makes sense that the original battery from 2017 is just reaching end of life, especially given the mileage. The battery charging system worked fine during the last service, so at least I know this is likely just a simple battery replacement rather than a more complex electrical issue. Going to ask the workshop to do a full check of the charging system while they handle the battery replacement, just to rule out any other problems that could cause premature battery drain. Hope this resolves all the error messages and starting problems I have been seeing.