[rotorwrench]

The cut out only cares about the amount of voltage that allows it to close the circuit on the electro-mechanical types. The diode type just allows current to pass the one direction. The generator charges only by increasing or decreasing current output on a third brush unit. Once the battery is in the circuit, it only needs to keep up with that applied voltage. With no battery to control voltage then it tries to put out the maximum output which will overheat it in short order.

The only drawback with three brush generators is the limitation on output amperage which is only enough for basic systems. If a person wants to add a bunch of accessories that draw more amperage then it would either need a 2-brush generator with a control unit or an alternator with a control unit.