Q8's Battery and Electrical Issues Need Urgent Fix

Had similar symptoms on a 2017 Q7 with the 3.0 TFSI engine. The starting issues and flickering lights pointed to a charging system problem. Initial diagnosis revealed both an alternator issue and corroded battery terminals. The alternator was not maintaining proper voltage under load, causing system-wide electrical problems. Battery testing showed it was heavily discharged due to the failing alternator. The voltage drop was significant enough to affect multiple vehicle systems. The fix required: Complete alternator replacement, Battery terminal cleaning and reconditioning, New battery cables, Full charging system diagnostic This was a serious repair job that took two days at the shop. The symptoms match your Q8 situation closely, the unusual system failures and dim lights are classic signs of charging system problems. Recommend getting the alternator output tested first, then check for voltage drop at the battery terminals. These electrical problems typically worsen over time and can leave you stranded if not addressed. The high mileage on your Q8 makes alternator wear a likely culprit.

Thanks for sharing your Q7 experience. Your electrical symptoms really do match what my Q8 is doing. The voltage regulator seems like the obvious starting point before replacing the whole alternator. Did the battery health test show any issues beyond just being discharged? Also curious what the total repair cost ended up being and if the charging system has stayed stable since the fix. I called my local shop and they can check both battery voltage and alternator output next week. Hoping to catch this before it leaves me stranded somewhere.

Can confirm the charging system has remained completely stable since the repair. The voltage check showed it was indeed the power supply causing problems, the battery was heavily discharged and failing. Unlike my Q7 case, your Q8 did not need a full alternator replacement. The battery health test revealed significant degradation beyond just discharge. The mechanic found the battery cells were damaged from repeated deep discharge cycles. The fix focused on installing a new battery and cleaning the battery terminals to ensure proper connection. The total came to 290 Euro, which covered the new battery, terminal service, and diagnostic testing. Much less than my alternator repair. The Undervoltage detected warning has not returned since the repair, and all electrical systems are functioning normally now. Smart move getting it checked soon, these electrical problems can cascade quickly when the battery starts failing. A proper diagnosis of the charging system will help prevent any roadside issues.

Going to the mechanic today turned out much better than expected. After reading about your experience, I specifically asked them to test the voltage regulator and check for any voltage drop issues. The diagnostic revealed a failing battery and some corrosion at the terminals, but thankfully the alternator tested fine. The mechanic showed me the battery test results, it was only holding about 40% of its rated capacity. Got a new battery installed and had them clean all the terminals and connections. Total bill came to 320 Euro, which included the diagnostic work. All the electrical problems cleared up immediately, no more flickering lights or hard starts. Really glad I caught this before getting stranded somewhere. The charging system is working perfectly now and the battery voltage stays steady even during cold starts. Thanks for helping me avoid an unnecessary alternator replacement.