Why positive ground?

[Cool Hand Lurker]

The question of why Henry Ford used positive ground for so many years comes up occasionally on Fordbarn. Some have said it is because it keeps the battery cables from corroding. I just read an article from the Digikey Co online library that stated the same thing so I think I will go along with that theory.

I have included info and a link to the article for those of you who understand this stuff better than I do.

PWM Controller Handles Multiple Topologies with Negative Input Voltages

By Ashok Bindra
Contributed By Electronic Products
2015-07-07
Traditionally, telecom and datacom equipment deliver negative DC output voltage, such as -48 V, for the system bus. The reason is simple: the DC voltage keeps noise low and can be easily generated from regular lead-acid batteries, normally around 12 volts. In addition, the negative supply keeps cables and copper wires away from corrosion. ….............

http://www.digikey.com/en/articles/t...input-voltages

[WestCoast]

electrical engineers know that electicity flows from neg to pos, not from pos to neg, so ford engineers used this system, its supposed to be more efficent, but who cares, just as long as it works and your car starts in the morning, ford changed because all other car manufactors went with neg ground

[Minn-Tex Lee]

I just finished reading the article and felt - WOW -if we need to know this to enjoy our Model A , we are in big trouble.
First - there is a big difference between negative ground and a negative voltage. Negative ground just means the negative side of the battery goes to ground or in our case frame.
Second - Negative voltage is only a reference point.
For example if you connect two 12 volt batteries in series the + and - at the ends would measure 24 volts.
However measuring from the + end to the center of the connections you would see + 12 volts. Measuring from the center to the other end (the - end) your meter would show - 12 volts.
The connecting point being the reference point.
At least that is the way I see it.
Lee

[H. L. Chauvin]

A Slightly Different Concept ..... FWIW:

Appears concepts in life always tend to be revaluated as we age.

In looking back, after only judging from what I saw in many former bold decisions made by my Dad ........ I think during our former Model A era ....... far more were thinking "Positive" (+).

[2manycars]

Interesting that the model T was 6 volt Negative ground. And when ford changed to 12 volts in 56, it went back to negative ground.

[Tom Endy]

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I have a couple theories on the subject:

Henry was somewhat of an obstinate fellow and his purpose may have been to confuse and confound the next 100 years of Model A enthusiasts.

Another theory is that Henry worked at an Edison plant before he became a car maker and surely understood that current flow was from negative to positive. Looking at a schematic he probably reasoned that in order for current flow to pass through the load it had to first travel through the frame and fenders and such with a negative ground system. Wouldn't it be more efficient to run the current from the battery immediately into the load? Then it could take its good old time finding its way back through the car to the battery.

Tom Endy

[mshmodela]

Back in the day as an Electrical Engineering undergrad student I never saw a single positive grounded system. As an RF Engineer with Motorola or while Phillips Medical I never saw a positive ground system. My Model A is the first positive ground ANYTHING I've ever seen. Are there any other cars that are positive ground?

One might ask if positive ground was such a good idea why then did it died out from modern use in cars?

[modelaer]

I read many years ago that the theory was: the positive battery terminal tends to corrode the most and the battery is held in place by a metal hold downs that are grounded to the chassis. Given that the corrosion produced by the battery is somewhat conductive causing a slow discharge; why not make the positive terminal ground potential so the battery will not discharge over time.

Good theory and I'm going to stick with it.

Pete

[1955cj5]

MG's were positive ground into the late sixties...1967 if I remember right....

[bbrocksr]

In the 6 volt era Ford and Chrysler products and a lot of others were positive ground. Most, if not all welders were positive ground. G M was the oddball with negative ground. When Ford and Chrysler went to 12 volt they also went to negative ground.
Bill

[Dodge]

He was tired of so much negativity after 15 million cars.....

[steve s]

Here's something I put together for our local club's newsletter when this subject came up a few years ago:

Why Negative Ground?

A recent forum discussion thread on the fordbarn.com web site motivated me to go back and look again at an article in the Skinned Knuckles magazine. The article, "Why Negative Ground?" was in the September 2009 issue, #398. The simple question about a relatively modern occurrence was asked by a reader: Why did all remaining positive-ground U.S. manufacturers switch to negative-ground in 1956? After extensive research seeking an answer, the frustrated editor concludes,

"Much as I would like to announce that we have an answer, unfortunately just the opposite is true. Not only have I not obtained facts, but I am also puzzled beyond belief that the wide variety of automotive historians and curators whom I questioned could not come with a factual answer."

One U.K. electrical engineer and museum curator who was queried on the subject replied, "You have opened a can of worms..."

The SK article includes a table showing ground usage by 35 car models since 1932. Twenty five of those used positive ground for at least part of their existence. The various models that became part of GM, except for Cadillac, always used negative ground, as did Duesenberg, Essex, Stutz, and Reo. Cadillac switched from positive to negative ground after WWII. Hudson switched from negative to positive ground in 1934, and then back to negative in 1956. The "universal" switch to negative ground never occurred in the U.K. Nash Metropolitans remained positive ground, and allegedly some US car models made for export to the U.K. are still set up with positive ground.

The various creative, speculative or bogus rationales supporting one or the other grounding usage that have been offered over the years, including the corrosion thing, are briefly reviewed. The fact is that in 1956 there was a sudden consensus that it would be a good idea to standardize, but exactly how and why that consensus emerged at that moment in time remains puzzlingly mysterious.

I think it's clear that there really is no strong argument to be made one way or the other, but standardization is a good idea, and, happily, it came to pass! Too bad Ford was on the wrong side of history, but it's no big deal.

Steve Schullery

[J Witt]

I had a couple of Alfa Romeos in the late 50's. They used positive ground Lucas electrical systems in the standard Giulietta roadsters, but the higher performance Veloce models used a Magneti Marelli negative ground system. If you worked on those cars (both awful electrical systems) you had to stay alert about getting the right parts. The Italian engineers just used what was available, as far as I could see, but I think the only criteria for the high performance stuff was weight, the MM starter, for instance, being about half the weight of the Lucas unit.

Often other considerations besides theoretical perfection drives the choice of design.

John

[1crosscut]

Now that most all of the automobile manufactures have standardized all their cars to negative ground. When do you think that they will get around to putting the gas tank fill spout on the same side?? Having it in the middle on the A's simplified filling up.

[mrtexas]

I can't think of a reason headlights, taillights, coils, and generator would care which way the electrons flow!

[ronn]

remember, many of the first cars built in America had steering on the right side of the car............... the models NRS Ford for example.
Today all of the steering whls are on the left side in America.
Pierce Arrow was one of the last to abandon right wheel steering.....
The masses dictate.

[Tom Wesenberg]

All I know is that when I was a little kid and did something wrong, I was positively grounded.

Studebaker, as well as several car and tractor makes were positive ground.

One day when I was about 13, while standing on wet ground over our well pit, I accidentally touched the plug wire on my 1950 Studebaker. I didn't care if it was positive or negative ground, but my hand was locked on for about 15 seconds.

[Gold Digger]

Way back when I was a teenager I bought a nice old 29 model a sedan. I new they were all supposed to be positive ground so I put the battery in that way but it showed discharge. I went threw the electrical and then checked to see if the generator motored and it did. I spent most of the night trying to make this thing charge before I discovered that someone had crossed the wires in the generator to make it negative ground.

[SeaSlugs]

Originally Posted by 1crosscut

Now that most all of the automobile manufactures have standardized all their cars to negative ground. When do you think that they will get around to putting the gas tank fill spout on the same side?? Having it in the middle on the A's simplified filling up.

or like in the 70's and behind the license plate in the rear.

[ian Simpson]

As an apprentice (1960-1965) I worked on many differing electric systems. All the British cars and motorcycles had positive ground. Also, electric fork lifts, tractors and delivery vans also had positive ground.

One thing I noticed is that corrosion moved from the negative battery terminal to many other circuit connections, but at reduced intensity.

I think the advantage of positive ground is that corrosion is spread upon multiple points so that it does not inhibit operation.