Car Alternator to Cheap Motor





Introduction: Car Alternator to Cheap Motor


This is my first instructables.

Because of my English i put more pictures and less words.

In this instructable i will try to explain how to convert car alternator to motor.

Step 1: Material Required

You will need:

- old car alternator

- servo tester

- Brushless ESC speed contorler

- 12V Battery

- 5V Power supply (old PC supply or some DC step-down)

Step 2: Disassembling

This is Bosch alternator from German cars in 1980.

First disassembl regler (two screws).

Then unscrew 4 screws from front (pulley) side.

After separating Stator and Rotor remove stator and diodes from housing (3 screws).

Cut off diodes from stator.

Step 3: Modifications

Isolate brushes.
I made this with angel grinder.
And solder some wires on both brush.

Step 4: Wiring and Assembling

I use PC power supply 5V for rotor, and car battery 12V for ESC (stator).

You can also use 12V on rotor, but motor will bi slow and spent 3 amps on rotor.

After wiring assemble everything back except diodes.
Some better ESC have switch for changing direction, but you can do manually switching two phase.

And that is all.

And one more think.

Please be careful, this is a powerful
motor and it can hurt you.



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      1 Questions

      I'm trying your experiment. My alternator has 4 wires,1 ground / neutral ( I believe).
      What would I do with the 4th wire?

      If your Alternator has 4 wires, three of them are a coil, the fourth is all of them joined up, watch this video on YouTube:


      I've read about people getting 1000W or more power from alternators modded like this. This is really a good idea for obtaining cheap motors for electric motorbike conversions.

      In idle speed consume 1,6 amps.

      When i put some load, speed little decrease and it can consume up 10 amps.

      Probably more, but my ampere meter can measure max 10 amps.

      I'm trying your experiment. My alternator has 4 wires,1 ground / neutral ( I believe).
      What would I do with the 4th wire?

      1 reply

      Think of an alternator as three different phases. (3 coils)

      They can either be wired in delta or y (what the author calls "star") configuration. In the y configuration, you can have a fourth wire, which is the common center point. In an ideal world this should be 0 volts and is a no-connect.

      You'll need to use a multimeter to find out which one that is. The common point node should both:

      1) Have the least resistance to any other wire.
      2) Have the same resistance to all other wires.

      From there, the controller is smart enough to tell the difference.

      More info:

      Hello, have you considered to replace the rotor coil with permanent neodymium magnets ?

      1 reply

      Hi Harry,
      Well, on rotor coil i adjust torque and speed.
      Permanent neodymium magnets are excellent idea if we use alternator like alternator.
      In that case we do not need power supply to start generate current.

      Hello, thank you so much. I managed to make the conversion but I was wondering if i can increase the power/torque by increasing the field voltage or current or increase the stator voltage to say 15 - 18 vdc as I'm using a 2-6s 30A esc.

      I made all the connections that connections using an esc( hsn30a by dys) but the alternator wouldnt run.

      1 reply

      Hey, it will work.
      Which voltage you use for rotor? Can you send me few photos on email that i can see, and a bit description.

      Reversing the alternator into a motor is a nice project. And because there are no magnets inside, you have to make them via the windings. But it then becomes a electric motor. Nice project.

      1 reply