Ground Strap vs. Ground Cable

[famous bob]

Yeah, seems like some discussion on different things here.

For the head to firewall, the flat braid is most common in my experience, but either works fine electrically. Flexing is the thing to consider there, since the length is ususally short. I have seen some older Jap cars with a small group of paralleled insulated wires and crimped into the same lug for a flexible ground.

For the main ground wire, the large stranded wire is the common thing. But, I have used large flat braid for that on a race car for many years with fine results. For DC and low frequency, the electrons do not care.

no comments on the motor plate ground?:scratch:

 

[moperformance]

Want to see a crowd of flat braided ground straps ? Look at a police car. They're added to hood, deck lid, doors, everywhere. I don't know if this has to do with their onboard computers, taizers, or both but it's well grounded.

Creates a "Faraday cage" out of the surrounding sheet metal. This shields the electronics.

 

[67Dart273]

Want to see a crowd of flat braided ground straps ? Look at a police car. They're added to hood, deck lid, doors, everywhere. I don't know if this has to do with their onboard computers, taizers, or both but it's well grounded.

Creates a "Faraday cage" out of the surrounding sheet metal. This shields the electronics.

This started a very long time ago in trying to create a quiet environment for two way radio communications. To show how 'bad' this problem can be, all you had to do "in the day" was tune in a weak AM radio station, and if there wasn't too much ignition noise.......just open the hood. Corvettes had a big metal shield mess around the distributor and wires because the body is plastic.

"Loose parts" such as hoods, doors, trunk lids can form what amounts to a diode, think "crystal radio." In WWII some POW's made successful 'crystal sets' using a sharp probe on the edge of a razor blade. Back then, blades were all steel, not stainless

This can cause a nightmare of frequency mixing problems (intermod) at places like radio sites, which, handily---are surrounded by chain link fences, a real bad offender

If you were to take a handheld radio ("walkie talkie") up to a busy radio site, tune in certain transmitters up there, then hold TWO SCREWDRIVERS with the blades touching, and rub them together, you will hear.............static in your handheld. This is caused by the screwdrivers acting as antennae picking up RF, and the "poor connection" between the two causing various intermixing of the transmitted signal(s).

This problem can be SO BAD that a good example is the Skyline Drive radio site in Pullman, WA. There were only 3 or 4 radio systems in that building, yet one of the transmitter PA (output stage) on one repeater was causing a mixing problem envolving the third harmonic of one of the other systems.

 

[KitCarlson]

I have an arch style building that is a great Farady cage. It is so good the garage door remote would only work at 2 feet when the door was shut. I solved the problem by making a passive antenna repeater out of a brass welding rod, one half in, one half out, thru a nylon bushing. It increased the distance to 30 feet, I can now open the door from inside the car.

Boxes for electronics does not shield electronics much, I/O cables are antennas bringing in, or radiate all sorts of signals. Cable chokes at entry are a must. I use surface mount chip inductors, and caps on all I/O of automotive ECU designs.

So to get the door remote to work, it is a good example of an I/O without choke. The rod lenght was cut for the correct wavelength.

 

[pishta]

My skin effect post was going back to my CATV days where the signal traveled on the exterior of the center conducter. AC/DC was never covered in that class, good to know. I still say strap as its more flexible from motor to firewall. Use star washer under both ends to get a good ground. Tuner imports run an Ebay ground straight to batt from about 6 different spots in the engine compartment in series (well, parallel in the pic ) as they have so many electronics. The hub bolts straight to neg post and the neon yellow color boosts power of 120hp ricer.....

 

[ir3333]

i have read that the stock neg pigtail from the battery to the rad should be avoided on aluminum rads because of electrolosis.

 

[straightlinespeed]

i have read that the stock neg pigtail from the battery to the rad should be avoided on aluminum rads because of electrolosis.

Interesting. I wonder if there is any proof of this? I believe that could happen no matter what.

 

[67Dart273]

Galvanic action, electrolysis is caused by chemical imbalance, not by grounding. What are we gonna do, make the rad support out of fiberglas?

 

[ir3333]

...the idea is that there is a current path through the neg. cable,rad, coolant and block
a simple test is the pos meter lead in the coolant and the negative lead on batt.terminal anything over .1 V indicates some current flow through coolant and a zinc anode should be used.
i read this on one of the larger rad manufacturers' web site but don't know myself.

 

[dodge71demon]

 

[ir3333]

.. the iron block and aluminum rad are dissimilar metals and the coolant if it has enough minerals or whatever in it becomes the electrolyte.
...would this be possible?

 

[nm9stheham]

Cute picture above.....Grounding IS a factor in this issue; there has to be a complete circuit path for the galvanic corrosion to proceed; it is a simple electrical circuit that has to be completed. Anything that can increase resistance in the path will reduce it and anything that makes the path better will increase the action.

Yes, it will happen naturally with any ions in the coolant, and that is the reason that a zinc sacrificial piece in the AL rad can be used to protect the AL radiator and to keep the AL from corroding. You can see an example of this in the galvanic chart here; zinc is to the left of the AL alloys and so will become the metal that gets sacrificed rather than the AL.

Regularly testing and treating the coolant to prevent it from becoming acidic is a common practice in trucks to keep this from happening. There are test strips used for coolant testing.

http://www.rowantechnology.com/technical-resources/galvanic-series/

Not sure how to totally prevent a ground path through an all metal AL radiator as pointed out by 67dart273, but avoiding a ground strap directly TO the radiator IF it has metal tanks has merit IMO. Of course, a lot of AL cored tanks in newer cars have plastic tanks so the AL core gets electrically isolated in that that way, but with rads like the Champions with their all-metal AL construction, then it is an item to be aware of.

BTW, with older brass radiators, the same galvaninc corrision was taking place all these years but we never worried about it or were aware of it as never became an issue for a very good reason. That's because the iron was to the left of the brass in the galvanic series, and so the iron became the sacrificial element and the brass was the non-sacrificial (more 'noble') element. That relatively thick cast iron's surface became sacrificed and we just never had any issues since it is cast so thick (for good reasons, obviously!). The opposite it now true with AL radiators since they are so thin walled (so that they CAN be good radiators).

 

[blue missile]

I know I'm way over the edge on this subject but regardless of the location of the battery, there should be a home run back to the neg post of the battery available to all electronics. While the negative buss bars are all connected to the body/frame that is a secondary path to ground. My car has three sealed discrete compartments, each with a buss bar and a large conductor back to the batteryAndrew

 

[rmchrgr]

Cable.

 

[nuttyprof]

Belt and suspenders. You will never have TOO good of ground, just like you can never have too many outlets.

 

[nm9stheham]

BTW for those who want a good flexible ground cable, check with welding supply houses; the ground cables used for arc welders usually uses a very fine wire and is a very flexible cable type versus the coarse wire cable used in most ground cables for cars. Welding cable also has a very chafe resistant outer jacket, as it is made to be dragged around on the ground.

 

[ntsqd]

Belt and suspenders. You will never have TOO good of ground, just like you can never have too many outlets.

But as was discussed you can have too many grounds.

BTW for those who want a good flexible ground cable, check with welding supply houses; the ground cables used for arc welders usually uses a very fine wire and is a very flexible cable type versus the coarse wire cable used in most ground cables for cars. Welding cable also has a very chafe resistant outer jacket, as it is made to be dragged around on the ground.

This usually prompts a discussion about how welding cable isn't intended for oily environments and the high heat of an engine bay. My local battery shop sells Carolprene cable for use as battery cable. See attachment, I've no worries from using this cable anywhere on a vehicle. I use cast lugs (no open ends) with adhesive lined Heat-Shrink to bradge between the cable's insulation and the body of the lug.

 

[KitCarlson]

Here is a good reference for underhood temperature requirements. A cable rated at 105 C will be acceptable if it is remote from engine.
[ame]http://www.eng.auburn.edu/apl/files/johnson.pdf[/ame]

 

[ntsqd]

I dunno, been using them on the engine for over a year on one vehicle and they've been on another for over 5 but that unit doesn't see much operation. No signs of any trauma to the insulation. I'm thinking that none of my older vehicles have the late model kinds of thermal issues that Johnson's paper is addressing.

 

[nm9stheham]

Wow that is a LOT of stranding in that cable! It ought to take a lot of flexing. Thansk for the link.

105C wire is an IEEE test rating and is continuous and for even inside of a closed raceway. Such wire can take higher temps on a transient basis.

Thanks for the interesting technical article link, but it is more for semiconductor and assembly survival, not for wiring per se. Exposure to air and heat and oil combined for wire insulation is a different animal. I used some old WWII dynamotor wires for remote battery wiring in a race car and it went into the engine compartment and never showed any issues on the isulation with many, many long endurance races.

 

[4spdragtop]

If you go with a strap, why could you not protect it with heat shrink tubing if need be??

 

[nm9stheham]

You could but it would just be a lot less flexible and you might put a lot of the stress on one or 2 points only. Heat shrink is not all that good for flexiing.

 

[ntsqd]

For strap you could go with the non heat-shrinking type of electrical tubing and just secure the ends with heat-shrink. That should retain most of the strap's flexibility.
The so-called "Liquid Electrical Tape" is promising, but I've never used it for anything, so that would be an experiment.

 

[RedFish]

I have a hard time believing this poll hasn't been knocked down already.
The one time I posted a poll seeking much needed feedback from other a-body owners, it was knocked down in less than 24 hours.

 

[straightlinespeed]

Red, I honestly didn't think this thread would run for so long either. I thought it would be a fast topic and done in a couple days. I do appreciate everyones opinions on it and thanks for the links for the cable.