S80 Overvoltage Fault Codes

I have an S80 too, and had similar symptoms. The fault memory was full of overvoltage errors, and the car generally wasn't happy. A weak battery can cause all sorts of strange electrical problems because the car's ECU (Engine Control Unit, basically the computer that controls everything) isn't getting the voltage it expects. Have you had your battery tested?

Interesting! No, I haven't had the battery tested yet. Was it definitely the battery in your case? Was it heavily discharged or just defective?

In my case, it turned out to be a heavily discharged battery. While a defective voltage regulator can cause overcharging (which leads to overvoltage), a severely discharged or defective battery can also trigger similar overvoltage errors in the car's system. These cars are sensitive to voltage fluctuations. It's worth getting it checked at a workshop.

Thanks for the advice! I took it to a workshop, and you were right, it was the battery. Replaced it for 290€ and everything seems to be working fine now. Cheers!