I had a 94 Golf. The alternator developed a fault, probably the voltage regulator part, it started overcharging uncontrollably, at first intermittently, but shortly it was doing it all the time. Battery voltage rose as high as 17 volts, headlights were super bright, the battery started to boil and spill acid.(lots of damage to the tray and nearby body work. New alternator fixed the problem although a new regulator might have done it cheaper, (assuming one of the brushes located on the regulator is worn to limit or stuck)

Similar problem on my 1978 Saab 99, overvoltage cooking battery and super bright headlights. This had the old 2 relay regulator which I tried to adjust without success. In the end it was one of the small discrete diodes (out of 6) that fed the regulator.(Not the main rectifiers).Managed to replace the diode and fixed it.

Both cases using a mulitmeter showed high voltage (>16 volts) when revving the engine. The voltage should not exceed approx 14.3-14.5volts on your car.

So I would say its a duff aternator/regulator and being a modern car compared to those I've mentioned, will detect the fault and shut down the car to protect the many electronics fitted.Depending on Alternator fitted, the regulator part is usually fairly easy (but not always) to remove and replace located at the back end of the alternator.

You could always try an alternator from a breakers.

Honda motorbikes of a certain era (Bear with me) are known for cooking their electrical systems not due to the alternator but due to the regulator/rectifier. Nowadays I imagine the technology has moved on (We fitted MOSFET units) but I suppose anything can fail.