240Dog,

The alternator does not make excess electricity if the voltage regulator is working correctly. The regulator keeps the voltage output of the alternator at about 14.5 volts which is the correct voltage to properly charge the battery. When the battery is fully charged, the voltage of the battery equals the voltage of the alternator and current stops flowing into the battery.

Other electrilcal consumers in the car draw current proportional to their resistance up to the capacity of the alternator in amperes. Thus an alternator is rated by the amount of current in amperes it can generate I.E. a 55 amp alternator.

There have been voltage regulator systems made that use a Zener diode to regulate the voltage, but these systems are inefficient because they have to dissipate energy in a resistor. They are usually used in a very low current circuits. The voltage regulator in a MB system controls the field current of the alternator to regulate the output voltage and needs no Zener diode in the circuit.

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