When very young I had an old mini. Neg ground which was very inconvenient because i was a licenced "radio amateur" and my home built transmitter was neg grounded. So I simply inverted the battery. I was informed of terrible consequences by plenty of people but of course it worked fine. The dynamo simply changes it's remanent magnetism on the spot and that's it. Of course the ammeter moves backwards, just remember that or change the connection.
Now apart from my radio equipment the was not a bit of electronics in the car!
Now apart from my radio equipment the was not a bit of electronics in the car!