Permanent Magnet Motors and Battery Recovery Pulse Charging Circuits and other NIKOLA TESLA Experiments

A variety of permanent magnet motors have been published over a long period. In many cases the author reinvents a device which in reality is a development of a previous invention.

My first contact with this type was when reading about the Engineer Robert Adams from New Zealand. This type uses several Permanent magnets with the same pole towards the driving solenoid which is pulsed to allow the rotor magnets which are attracted to the Iron Core of the Solenoid, to pass without restriction.

I must thank Patrick Kelly for his ever expanding e-book from which much of my most recent work/inspiration has been derived.

He reports that he was inspired by the same TV program that I also saw many years ago entitled "It Runs On Water"

This may be accessed via this link

I started making versions of the motor described above about 2006. Small versions with a rotor diameter of about 75mm as I had available some 1/4" x 3" Aluminium Alloy stock. Cut square sections were trimmed roughly then turned in my ancient Lathe. Almost all of my versions have used magnetic levitation to support the rotor (always horizontally) The first attempt used 1/4" diameter cylindical Neo Magnets  with a 1/8" dia hole.

I placed 10 of these magnets into holes drilled around the perimeter of the rotor. These were pressed into the rotor using a vice. The central supporting magnet was also pushed into a fairly tight fitting hole. A locating spindle made from a broken long 3mm end mill made from Tungsten Carbide which was driven into the mounting plate made from heavy duty kitchen flooring panels which seem to be a very hard resin based material. The supporting stationary magnet was fitted over this pivot with like poles toward each other. There is only a small amount of sideways force due to inaccuracies so a small anount of light oil is all that is required and works very well. This unit initially used a reed relay as a sensor to switch the energising power to the solenoids (2) in series. These magnetic switches work very well when used as intended! But when considerable BEMF is produced when the DC is removed and the stored energy is released as a pulse causing the contacts to weld!!

Move forward to more suitable available modern IC's which incorporate the properties discovered by Hall way back. This effect shows up as a variation of current through a conductor subjected to a magnetic field.

The Hall Effect devices I use are in the very small surface mount 3 pin package and are triggered by either polarity N/S. I have made a small PCB or more accurately a milled circuit board about 1" x 1/2" or 25 x 12.5mm containing all the components to bias and decouple the Hall Effect device and an amplifing NPN transitor including a SMD LED to indicate the state of play.

Using this circuit board to drive power NPN switch the unit functioned quite well but very soon turned to using high power MOSFET devices.

I obtained a few pre used devices with an approximate specification of 10's of Ohms ON Resistance and 600V Vds at 10's Amps. This type of device is very easily driven from a very small NPN transistor but must present a Gate Capacitance discharge resistance (in OFF state) chosen to suit the time constant at the operating rate or frequency. If too high the MOSFET remains ON!

With this circuit the rotor reached 7000rpm from 20v and 10000rpm on 35v I have an old regulated power supply with current limit of around 1 Amp.

I monitored the BEMF with an old Oscilloscope to be around 600v. This I believed to be too low as it did not increase with speed. Rather it peaked soon after building up the revolutions.

Closer observation on the Scope revealed a clipped pulse. After further thought and experimentation I obtained some much higher Vds MOSFETs at 1500v 4N150's and sure enough the BEMF pulse was now reaching more than 1500v still slightly clipped when spin speed was fast enough. This is showing that the internal protection diode is doing what it was intended to do! This also confirms the statement by Adams and why mechanical switching was his preference.


My preference has moved on to circuits without physical movement. The pulsing of the Inductive circuit is achieved using LOGIC switching at a similar Frequency.

My realisation of the equivalence of these two types was seen when I made a removable single coil driven version.  What I saw was that with no drive the ouput BEMF remained the same for a considerable time without the magnetic drive acting on the rotor. This continued to rotate due to the very low bearing friction and no cogging without the solenoid near the magnets. The Hall sensor/MOSFET driver was obviously still operating and not being loaded in a significant manner.

Replacing the rotor with a logically generated equivalent around 3KHz on that version and the same solenoid a starting point was established that did not require any accurate machining.

This device when further developed and the BEMF harvested and saved in a) 25uF @ 4000v oil filled paper capaitor could be charged  to 2KV. b) Later added a string of 5 x 3300uF @ 450v electolytics in series would reach close to the same voltage after a longer period. I was interested to see that just 4 in series would reach 1800v but without damage due to limiting due to the rapid leakage current rise at 450V/Cap. Put a resistor across each to make sure that come the next day or later you do not get a belt!

This early version was using a Ferrite Cored Bifilar wound transformer to extract the BEMF and rectifying the pulse with two 1000v rated diodes in series. A single one, was destroyed when the 600v MOSFET was replaced  as I forgot the rating!

I have found that the best result has been achieved using a bridge of the same diodes (BA159's 1000v 1A Silicon).

This Version runs at 5KHz & Using a MOSFET type 4N150

Reference to diagram to be added here

This later version is a variation that collects the BEMF by using a Series Tuned Circuit. The Inductor has one end connected to the -Ve terminal and the other taken via a Capacitor chosen for the Frequency of the drive. Which was 5000Hz. The capacitor used was 0.05+0.02uF 2000v - paralled. The coil of the tuned circuit was adjusted with a 16mm dia Ferrite core and was quite sharp to tune. Some other effects were noticed that as well as the sharp pulses at some point in the tuning range there was also a Sinewave at 100v p/p at 5KHz seen on my scope' at the centre point of the tuned circuit  A pair of diodes were put in series and taken to the previously used 25uF 4KV giving 1500V to 2000v depending on the supply voltage used 20 to 60v.

This next Version runs at 10KHz and also uses MOSFET type 4N150

Reference to diagram to be added here

These later developments have resulted in much improved results in terms of both collected BEMF and also the Sinewave amplitude.

Work on this type of device was not continued for a long time as I could not see how to use it in a practical application with the following exception.

This next Version is used to Restore or Rejuvenate Car Batteries

The same device almost as just described has been used for several years now to restore and charge most discarded Lead-Acid car batteries.

This is achieved by applying the pulses to the old battery via a diode from the high side of the inductor.

The very high voltage sharp pulse injects a very short but high current. The battery prevents the very high voltage unless there is no hope due to an internal open circuit.

My experience has been that few are not recoverable in the car battery case. However I have had almost no success with old Gel versions.

But charging new non-spill Gel lead-batteries by only using this type of charger prevents or minmises sulphating.

The sulphated car batteries are restored by the pulse method, slowly without overheating.

In several cases the terminal voltage when first tried measured 1v or 2v only!

However the process takes quite a while when highly sulphated.  If the terminal voltage leaps up to more than 12v immediately it is not going to succeed.  Normally there is a slow increase in terminal voltage and may take several days.

Initially I was chgarging until the terminal voltage reached nearly 14v as is the standard accepted value.

However more recently I have became aware of the very early published data which for some reason has been discarded.

This was highlighted by Peter Lindermann's Video lecture a couple of years ago "Battery Secrets".

In this the fact was stressed that the production of electrical power was by chemical action.

The Sulpher being released from the Sulphuric Acid during charging/discharge cycles that are incomplete.

By which I mean when charging the terminal voltage slowly increases and if not being overheated will max out at 2.7v per cell.

This means 16.2v not 14v should be aimed at.  After reaching this value there is a small decrease in voltage and indicates that the charge is done.

Any further charging will just release gasses and not improve the battery.

Poor batteries with too much Sulphating will fall short of this goal, but may produce a new light service battery for a cheap price.

It is quoted that as more cycles of this handling will improve the capacity back toward the original.

I have one or two that are good for running Radio Equipment. One can be used while another is on charge.

One caution is that there are harmonics of the charging pulses due to their very fast rise times of <1uS. So sensitive amateur radio equipment maybe swamped by unstable spurs. I have taken to using crystal controlled versions which use dividers to produce the driving square wave needeed. The frequncy is chosen to not interfere with the frequencies being used and is stable.

The range of the unwanted signals is not excessive but will be heard in your own equipment. The obvious solution turn it off whilst operating!!

© Michael Walters 2010 Website by WaterPigs Web Design

© Michael Walters 2010 Website by WaterPigs Web Design