Self-exciting a Car Alternator Using a Small DC Generator





Introduction: Self-exciting a Car Alternator Using a Small DC Generator

About: Its all about life hacks, tools, scientific & creativity instructables ~ electron7m


This instructable is for converting a field excited alternator into a self-excited one.The advantage of this trick is that you won't have to power the field of this alternator with a 12 volt battery but instead it will power-up itself so that you can use it as a normal self-excited home generator.

You can directly watch the step by step video.

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Step 1: Things Needed:

  1. An Alternator.
  2. Small DC motor/generator.
  3. 3 CDs.
  4. Rubber band.
  5. Drill Chuck.
  6. 12V Bike bulb.
  7. Multi-meter.
  8. Wires & tools.
  9. 1 - meter Plastic thread.

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Step 2: Making a CD Pulley:

Open up the pulley and the cooling fan mounted on the shaft of alternator with the tools.

Take 3 CDs.

Cut one of the three CDs such that its diameter reduces to 2 centimeter of the original.

Stick them together as shown in the pictures and then mount them on the shaft of the alternator in place of the fan. Mount everything else back on the shaft as before.

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Step 3: DC Motor/generator Polarity Check:

Connect the the small DC generator on the mounting frame of the alternator.

Connect a drill chuck to the shaft of the small DC generator and then connect that chuck to the CD Pulley with a rubber bands shown in the pictures above.

Since the shafts of the motor and alternator are connected to each other with a rubber band.So, when you will rotate the shaft of the alternator then automatically the shaft of the DC motor will start rotating.

A small voltage will appear on the output terminals at the DC motor.

Measure the voltage of the DC motor with a multi-meter and check the polarity of wires when the motor is rotated in clockwise direction.

In my case blue is the negative and orange is the positive.

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Step 4: Wiring:

The point 'B' on the body of the alternator is the positive O/P terminal and the remaining body of the alternator is the negative O/P.

The negative side of the diode is connected to the body of the alternator which is -ve. Connect one of the 2 field (ROTOR) wires to the negative of the DC generator as well as to the positive terminal of the diode.

Then connect the other rotor field terminal and the +ve terminal of the DC generator to the alternator's positive and then connect a thick wire to that positive terminal of the alternator which is marked as 'B'.

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Step 5: Performance Testing:

Now all you gotta do is connect a load to the +ve and -ve O/P terminals of the alternator as shown in the picture and you are done.

As soon as you rotate the alternator's shaft, you will find that it is generating electricity because the small DC Generator is exciting the field of the alternator instead of a 12V battery.

Well done!!!

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Full video



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    Please, is there any pictorial guide on how you did the rotor field connection or can you describe how you did that?

    What was the source and the specifics of the small DC generator that was used?

    1 reply

    an old cd player motor

    I am sure it works. But not for a very long time. The concept is good, but not so much the layout. You should go with more solid setup with quality pulley and such. JMHO

    5 replies

    Yes! As i said in my video that the setup is just for giving u an idea of better solution.CDs won't work for long obviously since my only intension was to teach you people this trick. . :)

    what does it do?

    Generates electricity, without needing a battery, to exite the generator of the vehicle

    exactly :)

    It generates electricity.. without any i/p power supply

    Cam a 12 V DC alternator be modifyed to put out 36 V DC ?

    1 reply

    remove the diodes and connect 3 rectifiers to the 3 phase output , u will get 36V DC