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Excitation Circuit


When the single rectifier is installed, the auxiliary battery is connected to the anode post while the main battery is connected to the cathode post. In some applications, the auxiliary battery may be connected in a towed vehicle like a trailer. If the trailer is uncoupled from the vehicle, the auxiliary battery is being removed from the anode post.  Because the alternator output is common with the anode post, depending on the nature of the alternator’s regulation system, if there’s no battery present on the anode post, the alternator may fail to excite at start-up in which case no charging would occur.

The excite circuit is enabled when we attach an additional wire (purple) which [ideally] gets connected to the starter solenoid.  When the purple wire gets triggered with 12v (or 24 volts on a 24 volt system), it enables the excite circuit to pass battery voltage/current from the cathode [main battery] to the anode [alternator] for a period of sixty seconds.  This insures the alternator’s regulator has the requisite excitation current to start generating power.  If the sixty second window is missed, simply turn the vehicle off, and then initiate the start sequence and the excite circuit will again stay energized for sixty seconds.

If the starter in not easily accessible, then ignition  switched system voltage is the next alternative. 


Note that customers can use one excitation trigger if needed, but not both at the same time.  If the alternator is externally regulated, the use of an excitation trigger may not be necessary.  If the alternator is internally regulated, the use of an excitation trigger is typically necessary.

When our “diode” module gets installed between the alternator output and the battery, the “diode” effect starves the alternator’s internal regulator from the necessary voltage that is normally present.  Because of this dynamic, two forms of excitation triggers have been provided.  The preferential excitation trigger is the starter momentary trigger.  System voltage is applied to the orange excitation wire during the cranking process, and goes back to zero volts when the vehicle is running.  This insures the excitation circuit is active and causes the alternator’s internal regulator to excite allowing charging to occur.

The secondary trigger is ignition-switched system voltage: system voltage is applied to the trigger wire while the ignition is on and when the vehicle is running, but voltage is not present when the vehicle is turned off.