VW Eos Battery & Electrical System Warning Signs

Last month I encountered similar symptoms with my VW Passat 2013 diesel. The battery voltage was dropping significantly during startup, causing electronics to malfunction and dashboard warnings to appear out of nowhere. Initially suspected a simple battery issue, but testing revealed an alternator issue was draining the battery. The alternator was not maintaining proper charging voltage while running, leading to progressive battery health deterioration. The repair required: Complete alternator replacement, Battery terminal cleaning and reconnection, New battery installation (the old one was damaged from repeated deep discharge), Power supply system diagnostic check This was a serious issue that needed immediate attention. Continuing to drive with these symptoms risks leaving you stranded and can damage sensitive electronic components. The alternator problems in these VW models often show up between 70000-90000km. Based on your description, strongly recommend getting the charging system tested properly. The symptoms match a failing alternator rather than just a weak battery. Both components likely need attention at this point to resolve the power supply problems completely.

Thanks for that detailed response, your Passat issue sounds exactly like what I was experiencing! Did you remember approximately how much the full repair ended up costing? And have you noticed any other electrical quirks since getting it fixed? My voltage regulator seems to be acting up again based on some recent battery voltage readings, so I want to make sure I fix everything properly this time.

I ended up paying 290€ for the repair last week, and it was definitely worth every cent. The mechanic diagnosed a heavily discharged battery that was beyond recovery, causing those electrical problems and voltage fluctuations. Since replacing the battery, all the undervoltage issues have completely disappeared. The dashboard warnings have stopped, electronics work perfectly, and the engine starts instantly every time. No more dimming lights or power supply concerns. The mechanic also performed a thorough charging system check to ensure there were no underlying alternator issues. The battery voltage now maintains stable readings, confirming the battery was indeed the root cause rather than the voltage regulator. From my experience, when the battery health deteriorates this severely, replacing it promptly prevents damage to other electrical components. Your symptoms match exactly what I experienced, so getting it checked soon would be wise.

Thanks everyone for the helpful insights. Just wanted to share how this story ended. Finally took it to a different mechanic who specializes in electrical problems. They ran a complete diagnostic and found both a failing alternator and corroded battery terminals. The voltage drop was actually worse than I initially thought. The total repair came to 460€ including: New alternator, Battery terminal cleanup and replacement, System diagnostic, Labor costs After the fix, the car starts perfectly and all those weird electrical glitches are gone. No more dimming lights or slow cranking. The mechanic showed me the old alternator and it was definitely ready to fail completely. Glad I got it sorted before being left stranded somewhere. The new shop did great work and actually explained everything they found. Really appreciate all the advice that pointed me in the right direction for diagnosis.