Reason for Neg vs Pos ground?

[Geoff Newcombe #4719]

#1.  Who you callin' a cockroach??

#2.  "People are strange, and there are so many of them!"  Annnd they vote!

   Geoff N.

[Otto Skorzeny]

#2.  "People are strange, and there are so many of them!"  Annnd they vote!

As Winston Churchill once said, "The greatest argument against democracy is the common voter."

Anyway, it would be nice to find some documented evidence explaining the standardization of negative ground rather than supposition or guesses.

The reasons given regarding corrosion seem dubious since, to my knowledge, electricity doesn't care where the circuit is grounded - just that it is. I've never experienced excessive corrosion on any positive ground vehicles I have owned. ( Ford 8N tractor, Humber Super Snipe, MG)

[Bob Hoffmann CLC#96]

OK guys,
Here's some information. I have a book called Automotive Wiring Manual published in 1920. It has wiring diagrams for all cars made before 1920. Cadillacs were + ground, but Buick & Chevrolet were - ground. I flipped thru all the pages & I feel that 6V - ground was the most popular followed by 6V+  and then both + & - 12V. Dodge had 12V -. Instead of adopting the Dodge 12V - system, the "industry" forced most everyone to go 6V +. The military demanded 12V or 24V. They KNEW what they were doing. Despite that fact, the auto makers STILL kept 6V systems WAY too long. 
Bob

[Otto Skorzeny]

That's pretty interesting, Bob.

What does it say about the military requirements for ground?

[Bob Hoffmann CLC#96]

Thanks Forrest.
The military statement was unrelated to the book. I was just remembering seeing both 12 & 24 V systems used  with military applications. Maybe someone has the answer re the ground.
Bob

[Jose Gomez CLC #23082]

Folks,

Just my personal views..!

This topic was raised in multiple boards including here with several points of views and comments as to the integration or migration (in some cases) for the automobile industry to implement a positive ground versus a negative ground.

Several views/comments made on one versus the other such as wire and battery terminal corrosion, extending the plug life, etc could all be correct but again there is no substantiated evidence of such, this primarily due to lack of standards or general collective data and studies back then that one was better than the other.

Although the standard body such as SAE (Society of Automobile Engineers) was originally set in 1905 in the USA, it was just to promote an exchange of ideas onto other societies.  In 1928 the idea for a society of engineers specializing in automobile electrical trade industry was address in the UK.

Since then these standard bodies had slowly implemented standard changes for the auto industry. If anyone sat on one of these standard bodies (ISO, ANSI, IEEE) meetings you wished you could have a root canal done without Novocain than meet at one of these, root canal is more fun.

Last implementation by the main manufactures was also a slow process, it did not happen overnight. What we know is all major USA manufactures GM, Ford, Chrysler and their respective subsidiaries used either or system. However with the introduction of the 12 volt systems in the mid 50’s (1955/1956) the negative ground was predominant the setup in the automobile industry but not fully implemented by all.

Footnote, 1948 UK manufactures star to use 12v electrical system, 1960 alternators started to replace the generators, 1965 the negative earth/ground was reintroduced.

I would suggest reading the “Automobile Electrical and Electronic Systems” by Tom Denton 3rd edition; it has a few notes on this topic, the footnote above were from his book.  This book can be found on-line.

Forrest, Bob,

If I recall the dual 12V battery system in military vehicles was use as a 24V for the starter/generator motor only, the rest of the electrical system lights, etc was 12V. The book Bob mention can be found at
http://www.archive.org/details/automotivewiring00wellrich

[Otto Skorzeny]

The lack of any readily available data or scientific explanation on the subject of automotive electrical ground leads me to believe that there are no real benefits of one system over the other.

In other words, whether a system is positive or negative ground makes absolutely no difference whatsoever.

I suspect that the choice to adopt negative ground systems as the universal standard was entirely arbitrary. Perhaps GM, by virtue of it's size decided to go negative  understanding that the the world would eventually follow. Perhaps, Jose's ISO, SAE, IEEE guys just sat down one day in 1945 and flipped a coin.

It's at least as plausible as any of the other theories posited.

[pullin]

OK, so I'm not totally familiar with this "positive ground" wiring scheme, but I'll toss in what I know about electronics:

In the US, we think about "conventional current", where the electrical current flows out from the positive terminal of a battery, through a circuit, and into the negative terminal. That is, positive current moves in the direction of decreasing voltage.

But consider that "current" is really electrons moving through the circuit in some manner, and electrons are negatively charged. So when we think of 1 Amp of current flowing from the +12vdc / positive terminal to the 0vdc / negative / ground terminal, the electrons are actually flowing in the opposite direction: from the ground terminal and into the + terminal.

In some countries, they refer to "electron current", which corrects for this. It's just defined to be in the opposite of "conventional current", so 1 Amp conventional == - 1 Amp electron.

This might not actually explain it, but it's worth knowing.

[mgrab]

My guess:
GM had two or more E. Eng's (much like Tesla vs Edison) that had conflicting opinions on which was better.  They probably sat down to lunch together are argued points much like this thread.....I've seen similar situations many times before. That could expain why Buick, Chevy, Cadillac etc....were oposite each other.....my 2 cents..

[RICK IN NC]

MGRAB   I think you've got it.  Satisfies me anyway.

[The Tassie Devil(le) (Bruce Reynolds)]

And I always thought it was because the Positive (+) meant that electricity was in abundant supply, and that Negative (-) stood for taking back.

Bruce.

[Glen]

This explains why we have conventional current and electron flow.  We can blame it all on Benjamin Franklin. 

http://rare-earth-magnets.com/magnet_university/conventional_vs_electron_flow.htm

Glen

[Warren Rauch]

  Someone did ask what Cadillac said in 1946. From the Nov1945 Serviceman
    A fundamental change has been made in the electrical system of the 1946-series Cadillac cars. For the first time, Cadillac cars have an electrical system in which the negative battery terminal is grounded. This change has been made to conform with other General Motors car electical systems. The reasons behind the use of a positive battery ground are no longer significant.
 Maybe the war did make them change. Warren

[Brett Cottel]

Was there a reason that for most of the early days of electrical systems Pos ground seemed to be the most common?

Any idea why the change?   

Was the change usually at the same time as the change to 12v?

Was this all the same around the world?

I have a 1962 Fordson Super Major Tractor (which is a English built Ford) that has the pos ground and 12V

[TJ Hopland]

I had late 50's Ford and Case tractors both were 6V +G.  I would guess it took longer for the industrial stuff to catch up.   I know I/O boats ran points till the mid 80's and did not make the switch to EFI till the late 90's. 

[Wayne Womble 12210]

Could be that the average Joe knows nothing about electricity and simply thinks of positive as being the working side and negative as being the ground.  How many times he stuck that battery in  wrong and fried the system, until someone woke up and standardized a negative ground system.

[TJ Hopland]

So  what happens when you get it wrong?  I imagine you wont get any charging but does it hurt anything?  I know its been done.  I was working on a 50 Nash last summer that was hooked up wrong.  It started and ran.  We did not figure it out till we starting trying to get the charging system working.   Nothing appeared to be damaged because we got it working but there was a stuck brush in the genny and the regulator was way out of adjustment so maybe that saved it?

[Otto Skorzeny]

You can fry some of the electrical components like lights and gauges if they are individually grounded negative and you hook a positive ground battery to them. You might start fires, etc.

[Wayne Womble 12210]

Actually wont hurt much on the very old cars, but as voltage regulators, radios, and electronic accessories came into use, it is more likely to be damaging.