Audi SQ5 Slow Start & Dim Lights Signal Battery Issues

Had similar symptoms on my 2014 Audi A6 3.0 TDI. The battery voltage issues started gradually, first with slower starting and headlight dimming, exactly like your case. The battery sensor was not the core problem, though it showed error codes. After testing, the main issue was the voltage regulator in the alternator failing to maintain proper charging levels. The low voltage condition was causing the battery sensor to report false readings. The battery testing revealed it was only getting 13.2V while running, instead of the normal 14.2-14.4V range. This insufficient charging meant the battery was slowly degrading despite showing okay in basic tests. Needed a complete alternator replacement as the voltage regulator was integrated. This was a serious repair since the alternator location required removing several components for access. The battery sensor was actually functioning correctly, it was detecting the genuine charging problem. Worth getting a full electrical diagnosis with focus on alternator output and charging system, not just the battery sensor. The battery sensor acts as an early warning system, but may not be the root cause.

Thanks for the detailed writeup on the charging system issues. Your alternator diagnosis matches my experience. The slow battery charge and voltage regulation problems on my 2017 SQ5 ended up being alternator-related too, not just the battery sensor like I first thought. Quick question, do you remember roughly what the alternator replacement cost you? Also curious if you had any other electrical gremlins pop up since getting it fixed? My battery health readings are still a bit inconsistent and I want to make sure I budget appropriately.

Since my alternator repair, the electrical system has been working flawlessly. The crucial fix was actually the battery sensor replacement which cost 315 Euro, this resolved the inconsistent battery health readings completely. The mechanic properly diagnosed and fixed the bad battery sensor, which was giving false voltage readings. The sensor now accurately monitors battery performance and charging levels. No more electrical gremlins or mysterious voltage fluctuations have occurred. The proper battery maintenance and monitoring through the new sensor gives me confidence in the system reliability. While alternator issues can cause similar symptoms, getting the battery sensor replaced first was the right call in my case. This less expensive repair solved the problem without needing major alternator work. Regular battery testing confirms the charging system is now maintaining proper voltage levels. A comprehensive diagnosis really helped identify the true culprit. Sometimes the simpler fix of replacing a faulty sensor is all that is needed rather than assuming worst-case alternator failure.

After dealing with that slow start and dim headlight situation, I finally got it sorted. Took the SQ5 to a different shop specializing in vehicle diagnostics. Smart move, they actually found two issues. The alternator was running at 13.1V instead of the normal 14.4V, and the battery health was at 60% capacity. Their battery testing equipment caught both problems that the first shop missed. Ended up needing the alternator rebuilt for 850 Euro plus a new battery for 280 Euro. Shop did thorough battery maintenance and testing before and after to make sure everything was fixed right. Three months later, all electrical systems are working perfectly, quick starts and bright headlights. Total vehicle diagnostics and repair time was about 6 hours. Much better experience than the first mechanic who just kept replacing sensors. Sometimes you need to find the right shop that really knows their stuff, especially with these complex electrical systems.