VW Up Battery Drain: Sensor vs Power Issues Decoded

I had a similar situation with my 2013 VW Polo. As someone with some hands-on experience maintaining cars, I initially thought it was just a battery issue. The symptoms matched yours exactly, dim lights, sluggish starts, and inconsistent battery voltage readings. Since my battery was relatively new, I suspected there might be more to it than just a weak battery. The workshop performed thorough vehicle diagnostics, starting with a complete battery testing procedure. They found that while the battery charge was good, the battery sensor was giving incorrect readings to the car's computer, causing the charging system to malfunction. The repair involved: Full electrical system scan, Battery sensor replacement, System recalibration, Final testing to confirm proper operation Total cost came to 315€ and resolved all the symptoms. The car has been running perfectly for over a year now. To better assist with your situation, could you share: Does your check engine light come on? Have you noticed any error messages on the dashboard? Does the problem occur more frequently when the engine is cold or warm? What does your battery voltage read when measured with a multimeter? This information would help determine if your issue matches what I experienced with my battery sensor problem.

Last service was done at 130000km and included a full electrical system check. After diagnosing more, I noticed the battery voltage drops significantly when starting, down to 10.2V. Using a multimeter to test shows 12.3V at idle but only 13.1V when revving, which seems low for proper alternator output. The battery health itself might not be the main culprit since its fairly new. The battery sensor readings through OBD show inconsistent values, suggesting either a failing sensor or alternator regulator issue.

Your voltage readings definitely align with what I experienced on my VW Polo. When I had my battery sensor issues, I also saw similar inconsistent voltage readings through vehicle diagnostics, it would fluctuate unexpectedly even with a healthy battery. The 13.1V reading while revving is particularly telling. A properly functioning charging system should show around 14.2-14.7V at higher RPMs. The low voltage reading suggests either the alternator isnt charging properly or the battery sensor is feeding incorrect information to the charging system. In my case, the faulty battery sensor caused the car to: Undercharge the battery, Provide incorrect voltage readings, Fail to properly regulate the charging system Before replacing the alternator, I would recommend having a specialist: 1. Test the battery sensor separately from the charging system 2. Check voltage drop across all major charging system connections 3. Verify alternator output directly at its terminals The battery sensor replacement fixed my issues completely, but given your alternator voltage readings, you might want to have both components checked. When my sensor was replaced, proper charging voltage was immediately restored to normal levels.

Thanks for the detailed replies. After taking my car to the shop today, you were right about checking both components. They found the alternator voltage regulator was failing, causing the inconsistent readings I saw with my battery voltage testing. The battery sensor was actually fine, the low voltage from the alternator was the root cause. The repair included: Alternator removal and testing, Voltage regulator replacement, System voltage verification, Battery health confirmation Total repair cost was 395€. After the fix, battery voltage now shows a proper 14.4V while revving and the dim lights issue is completely resolved. The diagnostic steps you suggested helped the shop pinpoint the problem faster. Really appreciate the input about checking both the charging system and battery sensor readings, as it led to finding the actual fault.

Dear people, I have a 2013 VW Up, 60 hp. When I accelerate the car to 2000 rpm, it only starts to go fast after 2000 rpm. When shifting to 2nd gear, it hesitates (jerks) a bit before accelerating again. Is anyone familiar with this problem? I've already cleaned the MAF sensor and throttle valve, changed all filters, spark plugs, and engine oil, but the problem persists. Thanks in advance

(Translated from Dutch)

Check the ignition coils for any signs of wear or damage, as they can cause hesitation and jerking if they're not functioning properly. If the issue persists, consider having a mechanic inspect the fuel injectors and fuel pump for any potential problems. Let me know how it goes or if you have any further questions!