The engine speed changes in a wide range. The terminal voltage of the alternator accordingly changes in a wide range. Don't look down upon the voltage stability. To keep the voltage at a certain value, it is necessary to regulate the output voltage. The voltage regulator prevents the too-high alternator voltage and overcharged battery. It also prevents the too-low alternator voltage and undercharged battery. Delcoribo provides good voltage regulators, all parts have passed strict tests before packing.