Peugeot 308 rough starting Terminal 30 issue

Terminal 30 usually refers to the main power supply in the electrical system. Interruption could be a loose connection, a faulty fuse, or even a problem with the battery itself. Have you checked the battery voltage? Is it holding a charge? A bad battery or a parasitic draw could definitely cause those symptoms. What's the mileage?

Mileage is at 146568 km. I haven't checked the voltage myself, honestly. Where exactly should I be looking for the voltage drop? Fuse box? Could a circuit breaker be the culprit?

At that mileage, a battery replacement wouldn't be unusual, particularly with modern start-stop systems putting extra strain on them. Locating a voltage drop requires specialized tools and knowledge. While you can check fuses for continuity, a proper diagnosis often involves tracing the circuit. Given the potential for electrical faults and short circuits, perhaps a visit to a workshop is the wisest course?

I took it to a shop, and it turned out to be a heavily discharged and defective battery. New battery, and all is well. Cost me 290€. Thanks for pointing me in the right direction!