Model A & B

Ford Garage

Solid State Generator Regulator

True Field Current Regulation

This information is worth repeating. I've had this setup on my Model B for a few years and am very satisfied with the performance.

This is James Peterson's solid state voltage and current regulator for use with an original generator, in combination with a solid state power diode cutout. I also like the Ford/New Holland 6 Volt 9N/8N Tractor Battery.

Top Ten List

This is the 'true' voltage regulator I prefer for several reasons:

  1. It provides true solid state output voltage and current regulation by means of sensing battery voltage and output current load, and by continuously varying the field strength (via input field current directly) to maintain the correct level of generator voltage and current output. It 'electronically replaces' the original movable third brush function on original generators and retains all the original generator appearance.
  2. It works on 6V positive ground systems.
  3. It works with original electro-mechanical generator cutouts, or solid state power diode cutouts. Cutouts are not voltage or current regulators, they are merely a way to electrically disconnect the generator from the battery when the engine is not running and there is no generator output. This is necessary to prevent burning up the generator when the engine is not running, since the battery would try to motor it against the stalled resistance of the fan belt and stationary crankshaft.
  4. It protects the armature from excessive current by limiting max field strength.
  5. It protects all the bulbs by regulating charging voltage to 7.2 volts maximum. Bulbs are always bright, and never blow out from generator voltage spikes.
  6. It protects the battery from overcharging by charging at the correct 7.2 volts max, and delivers diminished current as full battery capacity is approached. This minimizes boiling and gassing of the battery electrolyte.
  7. It enables good generator current output at low rpm.
  8. It is about the closest you are going to get to alternator charging and regulation performance using an original generator.
  9. What you see in the picture is what you get. It is already attached to a heat sink which is silver-soldered to a new generator band.
  10. It is quality made and works as advertised!

What it doesn't do:

It doesn't increase the max current capability of the generator beyond the standard 18-20 amps (about 10 amps is 'safe'), so if you are running halogen bulbs everywhere and drive mostly with lights on, then it might not be able to keep the battery up with that level of sustained load.

It works great on Model A's with a reasonable load. Turn signals and extra brake lights are fine. LEDs are also fine, as they use less power than incandescent bulbs typically.

I do about 50% of my driving with headlights on, and have been using this since early 1999. I haven't had a single problem with it other than I initially hooked it up wrong. There are only two wires, and it does make a difference! Read the instructions first.

The field wire which normally goes to the third brush attaches to the screw stud on the regulator in the picture. The regulator has two other wires; the brown one goes to the ground brush, and the orange one goes to generator output (battery) terminal brush.

There is a small green loop wire on the circuit board. This loop is left alone when using an original mechanical cutout. You cut the small green wire if you are using a solid state power diode cutout. This changes the regulated voltage output from 7.2 volts to 7.9 volts.

The reason for this capability to modify regulated voltage is because there is a typical 0.7 volt voltage drop across a power diode as used in cutouts. With this provision for setting the output voltage, the battery charging voltage seen by the battery remains at the correct 7.2 volts, regardless which type cutout you use.

Disclaimer: I think I accurately described the functions and operation of this regulator, but if you have any questions, contact James and ask him. For inquiring minds who need to know, this little circuit board seems to have a 3 lead regulator, a transistor, 3 diodes, and 3 resistors on it.

I don't know the actual regulator schematic, but what it basically does is regulate both generator voltage and, current output by continuously regulating the field strength according to the sensed battery voltage and current draw.

So, if you want to get one of these great devices, you can get it direct from the electrical engineer who designed it and makes them. ($85 postpaid, I believe). Do not confuse this one with the Nu-Rex knock-off sold elsewhere. Get the good one from James!

Contact:
James Peterson
P.O. Box 912
Bend, Oregon 97709
541-389-0438 home


The following text is James Peterson's own reply to questions posted on ahooga.com, and offers added clarification and understanding of the superiority of switched field current regulation over various other output regulation methods. Reprinted here with his permission.

Posted by James Peterson

There seems to be a lot of curiosity and confusion on how voltage regulation is achieved in a automotive generator. Prior to the late 1930's the auto generator had what was called a field brush. The purpose of the field brush was to provide a manual means of controlling the strength of the field magnetism. The stronger the magnetic field, the more power the generator would produce and vice versa. This enabled the car owner a means of manually controlling the charge rate.

The moving of the field brush was like turning a variable resistor. This system relied on the battery and electrical load to hold the voltage down to a safe level. An accidental loss of load or battery connection caused the generator to generate very high voltages and damage the generator. This was primitive by today's standards, but it worked.

Then came the mechanical voltage regulator. It used a voltage sensitive relay to monitor the output of the generator and in turn provided rapid pulses of current to the field in the correct current on to current off time periods, to maintain a reasonable stable output voltage. This is referred to as the duty cycle.

The more on time verses the off time equals a higher charge rate. This is a very efficient and desirable method of controlling a generators output voltage and this principle is still used today on all modern generators and alternators. It enables a small amount of field current to accurately and efficiently control a very large amount of generator output current.

The following describes various methods of voltage regulation and their advantages, disadvantages and typical uses.

SHUNT REGULATION: This type of regulator is connected to the output of a power source. It provides a varying load to the source to try and maintain a constant output.

Advantages: It provides some degree of voltage regulation over a narrow input range.

Disadvantages: Very inefficient. A large amount of power is lost in heat.

Typical uses: Normally used in radios from the 1930 & 1950's. Not suitable for use with automotive electrical field generators.

SERIES REGULATION: This type of regulator is connected to the output of a power source. It provides a varying series resistance to the load to try and maintain a constant output.

Advantages: It provides some degree of voltage regulation over a wider voltage range than the shunt regulation.

Disadvantages: Very inefficient. A large amount of power is lost in heat.

Typical uses: Normally used in radios and consumer electronics from the 1960 & 1970's. Not suitable for use on the output of automotive electrical field generators, because as the series resistance increases during regulation, the generator output voltage increases causing a runaway effect in the generator and creating high currents in the field and some commutator arcing.

SWITCHED REGULATION: This type of regulation uses pulses of varying duration to control the output. This regulation causes the output to be switched on and off at a rapid rate with the on duration verses the off duration varying to match the output voltage requirements.

Advantages: Very efficient. Seeing as the regulator is either fully turned on or off, there is very little heat produced because of resistance and it has good regulation characteristics.

Disadvantages: Produces some voltage ripple. Not suitable for use on the output of automotive electrical field generator, because as the regulator is switched off the generator voltage increases causing a runaway effect in the generator and creating high currents in the field and some commutator arcing.

Typical uses: Normally connected to the field windings in modern alternators and generators to provide excellent output voltage regulation.

I hope this helps clarify how voltage regulation works.
James Peterson

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