I Finally Got My 4 Bifilar Coil Pulse Motor Generator Running

Hook

I fired up the 4 bifilar coil pulse motor generator on my 12 V bench and it surprised me how fast those little coils spun the rotor and still charged batteries.

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I flipped three switches, the rotor took off with a squeak, then settled into a smooth whine. Voltage on the charging batteries climbed from 20 V to 24 V while the drive side held around 21–22 V. The speed looked higher than what I usually get from bigger coils on the same voltage.

What you'll learn

You’ll see real-time battery charging, how close-placed coils trigger each other, the long flywheel spin-down, and why a simple bifilar coil pulse setup can still light a bulb and charge batteries without fancy parts.

From the bench

Everything ran on four 12 V batteries in parallel giving roughly 48 V to the coil pack but still operating as a 12 V system. Two coils sit at about 800 ohms each. One carries a reverse diode on the ground side just to test. The rotor is 3D printed at 15 % infill with weight on the outside, mounted on a 5/8 bearing with a quarter-inch center hole. A couple magnets are taped because one is a little loose and it shakes the table at one particular speed.

How it works / what we changed

I used a basic Bedini SSG stem-cell style connection without the usual resistance or extra diodes. The generator clip has a diode on the negative. When I turn one coil off the other keeps running and the voltages separate—one climbs to 24 V while the other drops to 21 V. The close spacing of the coils lets them set each other off automatically. After power down the rotor coasts for over seven minutes of useful spin and keeps turning for ten.

coil pack

The coil pack consists of four small bifilar windings mounted close together on the 3D-printed frame. Because they sit near each other the magnetic fields interact and help trigger the next pulse. All four coils are wired in parallel. With the 12 V battery bank this gives the equivalent of about 48 V across the pack while the system still runs at 12 V nominal. The small size of the coils in the pack seems to reach higher speeds on 12 V than some of my larger coils that prefer 24 V.

bifilar coil pulse

This bifilar coil pulse motor uses simple bifilar windings without added resistance. Each coil measures around 800 ohms. The pulse comes from the basic SSG-style connection and the generator clip with its diode. When running, the bifilar coil pulse charges the batteries at 18–24 V while the rotor spins fast enough to produce visible generation. Turning one side off shows the remaining bifilar coil pulse still drives the rotor and the voltage on its battery continues to rise slowly.

Builder checklist

• Four bifilar coils wound and mounted close together
• 12 V battery bank (four batteries paralleled)
• SSG-style wiring with generator diode on negative
• 3D-printed rotor at 15 % infill, magnets on outer rim
• 5/8 bearing with quarter-inch shaft
• Multimeter ready for voltage and inductance checks
• Optional reverse diode on ground for testing

Troubleshooting

If the rotor shakes badly at one speed, check that all magnets are secure—duct tape fixed mine. Voltage climb is slow; give it more time on the little coils. If one battery climbs while the other drops, that’s normal when only half the coil pack is switched on. Flywheel spin-down is slower than expected; that’s a good sign of stored energy.

Safety

Keep fingers clear of the spinning rotor. The voltages stay low (12–24 V) but charged batteries can still spark. Watch for loose magnets flying off at speed. Work in a clear area so the long coast-down doesn’t catch anything.

FAQ

Q: How long does it spin after power off?

A: About seven and a half minutes of useful spin, total ten minutes before it stops.

Q: Do I need 24 V for these coils?

A: On this small bifilar coil pack 12 V gave higher speed than I expected from bigger coils.

Q: Why the reverse diode on ground?

A: Just testing; not sure if it changes anything but it’s easy to try.

Related on this site

• How to Build a Pulse Motor: Parts, Coil Placement & First Spin
• Pulse Motor: What It Is & How It Works (Beginner Guide)
• Bedini Motor & SSG Circuit Guide (Beginner Bedini Explained)
• How to Wind Coils for a Pulse Motor (Step by Step)
• Pulse Motor Battery Charging: What Experiments Show

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