Volvo S80 Electrical Issues

Hey, those symptoms sound familiar! I had a similar problem with my 2012 BMW 3 series a while back. I had weak starts and flickering lights, and after some investigation, it turned out to be a faulty battery sensor. The sensor was sending incorrect voltage readings to the car's computer, which messed with the charging system. Have you tried testing the battery voltage while the engine is running? That might give you a clue. Also, check if the sensor itself looks damaged or corroded.

Thanks for the quick reply! I haven't checked the voltage while running yet, but I did inspect the sensor, and it looks okay visually – no obvious damage. Where exactly was the battery sensor located on your BMW? And did you get any specific error codes related to the battery or charging system?

On my BMW, the sensor was integrated into the negative battery cable terminal. As for error codes, yes, I did get a code related to the battery voltage being outside the acceptable range. It wasn't immediately obvious that the sensor was the culprit, but after some troubleshooting, it became clear. Given that your Volvo is showing similar symptoms, and you've checked the basics, a faulty battery sensor is definitely a strong possibility. If you're not comfortable diagnosing it yourself, I'd recommend taking it to a workshop for a proper diagnosis. They can use a scan tool to check for any related codes and perform further testing.

Thanks again for the advice! I took your suggestion and brought it to my local mechanic. They confirmed it was the battery sensor. The repair cost me around 315€ including parts and labor. Now the car starts perfectly, and the lights are steady. Problem solved!