[Jaydee]

Do not disconnect the battery whilst it is running. The alternator needs a voltage signal, if it doesn't it can run away and produce over 18volts and blow any electronics. This can happen if you jump start a car with a open circuit battery. If you suss an alternator, just strike it with a hammer whilst the engine is running, this sometimes kicks it into life, when the brushes are worn or there is a loose connection. it will get you home, maybe.
JD