Q5 Alarm System Dead: Aux Battery Warning Alert

Had a similar electrical issue with my 2020 Audi Q7 40 TFSI. The system diagnosis revealed auxiliary battery failure causing multiple alarm system malfunctions. The main symptoms matched yours, alarm system failure combined with sporadic electrical warnings. Initial battery alarm warnings started appearing on cold starts. The root cause was a degraded auxiliary battery, which serves as a backup power source for the alarm system. This auxiliary battery problem requires specific testing equipment to properly diagnose. The repair involved replacing both the auxiliary battery and checking the voltage regulator that maintains its charge. In my case, it was a serious issue since the failing auxiliary battery was starting to drain the main battery, which could have led to complete electrical system failure. A proper system diagnosis should include: Voltage testing of both main and auxiliary batteries, Load testing of the charging circuit, Verification of the voltage regulator functionality, Full electrical system scan for related fault codes Best approach is to request comprehensive electrical testing focused specifically on the auxiliary battery system before any parts replacement. The symptoms strongly suggest auxiliary battery failure rather than a general electrical issue.

Thanks for sharing that detailed experience. Having gone through almost identical auxiliary battery issues with my Q5, your description really resonates. The system diagnosis steps you outlined match what I faced. Quick question, do you recall the final repair cost for the auxiliary battery replacement and testing? Also, have you experienced any related car alarm or battery signal problems since the fix? Asking because after my repair, I noticed occasional system warnings during the first cold week, but they disappeared completely after that.

Thanks for asking about the follow-up. Since my last visit to the mechanic, where they fixed the Additional battery alarm system defective warning, everything has worked flawlessly. The complete battery check and replacement cost me 330 Euro, which covered both parts and labor. This included a thorough system diagnosis of the alarm system components. The repair has proven to be effective, no more warning lights or car alarm issues, even during cold weather. The new battery installation solved all the electrical problems I mentioned in my previous post. The auxiliary battery is now maintaining proper voltage, and the alarm system functions exactly as it should. Looking back, ensuring a complete battery check was crucial for proper diagnosis. The investment in replacing the aging battery was worth it to prevent potential system-wide electrical issues. The reliability of the alarm system since the fix confirms it was the right solution. For reference, make sure any repair includes testing the charging circuit, its a critical step that some shops might skip during basic battery alarm troubleshooting.

Following up on this thread to share how it all worked out. Finally got my Q5 properly fixed after the earlier misdiagnosis drama. Took it to a certified shop that specializes in electrical systems rather than the previous general mechanic. The repair process was straightforward once they actually knew what to look for. They ran a complete diagnostic on both batteries and found the auxiliary battery was indeed failing. Total bill came to 290 Euro for parts and labor, way better than the 800 Euro wasted earlier. The car alarm system now works perfectly. No more unusual battery warnings or electrical glitches. The new auxiliary battery completely resolved all the symptoms. Best part is the shop actually showed me the test readings before and after, proving the old battery was the root cause. Quick tip for anyone facing similar issues: insist on getting the auxiliary battery specifically tested. A basic car battery check wont catch these problems. The initial misdiagnosis happened because they only looked at the main battery. Got my money back from the first mechanic too. Showed them the actual repair invoice and diagnostic results, and they agreed to refund the misdiagnosed work.