Are the braided type ground straps less efficient than an insulated cable? I have new 2/0 positive cables to go on my car and a braided strap that I have not installed yet. Should I exchange the strap for a cable?
You need one of these.
The prevailing opinion on the forum seems to be that a braided strap is not a good thing . . . I'd like to know more on the experiences that arrive at this conclusion, braided straps were very common on all 6v systems for a great number of years. One thing about 6v systems though - 6v requires really generous, heavy cables, 12v seems to get by on wee, stingy cables - don't use 12v size cable. In fact, the best thing you can do for a 6v system is go to your local welding supply, and get 1/2" fine copper wire cable used on arc welders to make up your own cable. That way you're assured of an adequate "pipeline" for 6v power.
I like to use the braided one along with one to the motor. I use welding cable.
I have the same question is Rich — why the negativity on braided ground straps?
Seems like they can have plenty of cross section to handle the load, and as Rich pointed out braided straps were very common in the 6-volt era.
I'm using one on my 26 roadster pick up . No problems here.
I had a slow cranker and couldn't figure out why. One time I had a no start condition and after an extensive crank noticed a "cooking" odor. when I removed the rear floor I found it. Perfectly good looking braided strap with clean connections on both ends was smoking. Replaced it with a piece of welding cable (which I had laying around) and it cured the cranking problem. A frame to engine or trans strap isn't a bad idea either.
My '24 seems to do fine with a braided ground strap. Just lucky I guess.
In the book Henry's Wonderful Model T by Floyd Clymer, there is a picture of workers in the "frame department" in about 1922. The caption mistakenly identifies the year as 1914. A close look at the picture shows an insulated CABLE as a ground connection. The problem with the woven ground strap is the individual wires can get separated and instead of having one large conductor, you have several small conductors trying to handle the current. One of those small conductors is always going to be the carrier until it gets too hot, then another wire will take over and so on and so forth until the entire strap is hot and creating high resistance. This condition can happen in a matter of seconds. That's why the insulated cable or finer wire welding cable works. The insulation binds the small wires tightly together creating, in effect, one solid flexible conductor. A good way to check for any loose connection in a wiring system is check the temperature. High temperature = high resistance and vice-versa. Just my 25 cents worth.
I hate to differ here but there is a lot of misinformation in this thread. Braided ground straps are not weak unless they are made for a 12V system and thus contain less copper. The ground strap on many battery installations is very near to the ground connection (typically the frame) and a heavy cable is too stiff typically and can actually fracture the battery case if a short stiff cable is connected between the battery and a very nearby ground.
As for a cabled up bundle handling more current than the same conductors spread out - that is backwards. If you take a number of equal size conductors and put them side by side with a bit of space between them then if the ends are joined that side by side cable will handle more current than if those same conductors are placed next to each other in a cable and thus touching each other tightly in that cable. The reason is that the more air that can get to the strands the more cooling of the conductor and the more current it can handle. In fact a conductor if flattened out and placed as a copper trace on a printed wiring board can carry a lot of current compared to the same conductor cross section made into a wire. Same reason - better cooling of the flattened out current carrying path.
I am not opposed to welding cable being made into battery cables and those can work very well but they can also not work well at all if the ends are not properly installed to thus provide the rest of the path for the higher 6V current at the ends of the cable. I have seen some pretty poor battery cables on T's that were home made from very high quality welding cable. Finer strands DO typically make the cable more flexible which may or may not be deisrable depending on how the cable is mounted at the ends and supported in its patch from end to end. T guys in general tend to overthink everything electrical into a "more is better" idea that often installs more problems than are prevented.
In Dan B's post above in the link Lang's sells a ground cable that is a flat strip of copper that the ad says is original. I've never seen anything like that. This cable is on a frame I have. It may not be original but it's old. It has some kind of spring part toward the end where the terminal was.
I used the braided cable from langs does great!! Tim
Ford used the copper strap ground in later '24, earlier used the braided cotton cover round cable for ground. Photo below off a '23 chassis.
1924 Ford Service book photo showing copper strap.
IMO, the modern flat woven cable works for good ground too. Keeping all battery and frame connections firm and clean.
My Sept. 1921 parts book list three ground cables; 5048 20" 1919, 5049 9 5/8" 1919-1921 and 5050 1920 11 1/2" (shows a cable in the illustration). By 1928 it was 5049-B ground connector 1919-1927 (shows a flat strap in illustration).
The "technology" of the braided ground strap must have been pretty efficient as these are the ground straps needed for a WWII jeep. 6v negative ground system, but notice the number of ground straps needed for efficient electrical circuits.
And the Model T had one strap and the hard points on the motor mounts to grame to complete the starting circuit.
For whatever reason the old style braided cables go bad. I've seen it happen and am talking through personal experience. I don't know why it happens but it does. If I had one on another car it would be one of the first things to disappear and I'd recommend the same to anyone else.
Any cable can go bad whether it's flat, cable or woven.
The only problem with Lang's ground straps, which are almost correct, is they need to be zinc plated. NOS originals used to be fairly plentiful, but no more! I used the last one I had on my 1925 pickup. If I purchased one from Don, I would get it properly plated.
Had a flat, braided ground strap die on tour. Car had no power anywhere. The ground strap was connected and clean. No one could figure out what was wrong (250+ years of T experience working on it).
Got home and after yet another frustrating day of troubleshooting the problem, my truck driver mechanic came over, DRUG me back into the T barn and in about 3 minutes he had it running identifying the bad ground strap.
Only on very close examination could you see a faint brown area that ran all the way across the strap near the battery terminal. The strap had be out of the car and in good light to see it.
Ironically, I found the same problem on a friends car several months later!
In a word Tommy, No.
I get real confused when the forum talks about 12v and 6v wire when talking size...I only know wire by gauge (AWG) and maximum voltage rating plus other characteristic ratings...Help
Then to add confusion to the equation, most of the currant runs on the surface of a wire, not the inner core
That's current and surface of the wire should mean the wire portion not the surface of the insulation
What I have learned and read; the initial surge of electrons are traveling along the surface (the easy path) but as the current continues the strands get saturated. So the electrons can be traveling through the wire not just on it. Maybe that's too simple but so am I!
Back in the '80's, I bought a nice clean little "used" Mazda GLC that was about 5-6 years old. Ran just great and was completely trouble-free for many years. Then I began to have a bit of trouble with the starter. Had to fumble around, twisting the key a couple times before the starter would "kick in". Well, long story short, it got worse and worse until one day, it wouldn't "kick in" at all! With my lack of knowledge of anything electrical, I just picked up a new solenoid, as that, in my experience anyway, is the usual culprit. Still no go! Lots of checking, another solenoid, etc, etc, still no go! Finally "bit the bullet" and went to nearest Mazda Service Agency and got what I thought was a "fast answer" from a service writer and a mechanic. They told me to replace the braided ground cable. Dumbest thing I ever heard of, right? Ground cable looked fine! But, not knowing what else to try, I put on a new ground cable. BINGO!!! No more problem! Couldn't believe it, and it sure made me feel stupid, however,....I am now a believer! Yes,.....braided ground cables "DO" go bad, and you sure can't always tell just by lookn' at 'em! FWIW,.....harold
I installed the reproduction flat copper ground strap on my car. Just a few seconds of starter motor operation made the post clamp too hot to touch. I had not noticed there was a ridge inside the clamp which would not allow a good contact with the battery terminal.
Some polishing with the Dremel sander tool has it working cool as a cucumber now.
What I would like to know is: What is the cross sectional area of the copper in the braided ground strap? Knowing that it could be compared to AWG wire sizes.
>What is the cross sectional area of the copper in the braided ground strap?<
0 circular mils in this reproduction strap; it's braided steel:
In case anyone is wondering, the copper strap type ground is not a solid piece it's made up of strips of sheet copper with the ends affixed to the connectors to make the pack.
I wonder if it's the modern braided type that is having the problem. The old school 6 volt type seems to go on forever and only seem to get replaced when the clamp goes to heck. Is the wire used in the modern braided strap plated copper or is it something else?
Mark - John Regan's explanation in his post above served to "jar my memory" in regard to the problem I had with a braided ground strap in my old '70's Mazda GLC. John said,....."Braided ground straps are not weak unless they are made for a 12 volt system and thus contain less copper." It's been a long time ago, but I remember that Mazda mechanic telling me that those Mazda GLC's had a braided ground strap that was either aluminum, or, had some aluminum content. In other words, I'm not sure if they were ALL aluminum, or, if like John Regan said, they were aluminum and merely "contained less copper". At any rate, like so many other things nowadays, Mazda must have tried to get away with a cheaper braided ground strap and just plain cheapened 'em up a bit too much and got caught at it! Again, I'm talking about things I know very little about here, but I do know that aluminum is CHEAPER than copper, but not as good of a conductor of electricity! And I guess for that reason, nowadays, as opposed to back in the old days, ya' can't just look at a braided ground strap and ASSUME that it's O.K., just because it LOOKS O.K.! FWIW,.....harold
The only ground straps I have found recently are also for 12 volt systems and rated at 2 gauge instead of 0 or 1/0 (original).
00 or 2/0 (+ 10% extra) gauge is even better.
It really does not make a lot of difference braided or not on the ground strap, the most important part of a ground strap is the GROUND it self. To be effective it you need to have clean bare metal where you attach the ground strap to. Just pushing a bolt through the hole and securing it with a nut, ain't gonna cut it.
Use a unplated nut and bolt and use unplated washers under the head of the bolt and under the nut. The bolt must be a tight fit on both the hole in the strap and the hole at the ground point.
After they are tight and good contact you can paint the outer surfaces to stop the rust.
I'm going with the woven ground strap that I have. The cables I made up from 2/0 welding cable, soldering on ends and using heat shrink. The battery is a new Napa battery. ( I work at Napa.) I will make sure all connections are clean and tight.
Brass Car Guy, why unplated hardware ? Clean metal at the point of contact for frame and cable, makes sense, but what difference does plated fasteners make ? Inquiring minds need to know !
Greg, The reason why 12V or 6V is a factor in wire sizing is explained by Ohm's law. Current = Voltage/Resistance or I=E/R for short. So for a given load resistance (R), doubling the voltage (E) from 6V to 12V halves the current (I) so the connecting wires for 12V operation can be of smaller wire gage than 6V operation yet have the same losses; voltage drop and power dissipation (heating).
Regarding your comment that most of the current flows on the surface of the wire rather than the core; current density being largest near the surface of a conductor rather than its core is known as skin effect. The phenomenon is only applicable to Alternating Currents (AC) and typically only becomes a significant concern when the operating frequency reaches the kHz range. For example, the skin depth of copper wire is about 0.333" at 60Hz so not a factor unless your AC line cord wire radius is larger than that. The Model T magneto outputs an AC voltage but even running the engine at 2500 RPM translates to the magneto operating frequency of 333Hz and skin depth of 0.140" so not an issue unless you are running larger Magneto wires larger than 1 AWG copper (0.289" diameter).
For those of you who just have to have a braided ground strap, there was an NORS one made expressly for a Model T on ebay a few days ago.
A couple of corrections to my previous post. The statement in reference to Ohms's law; I=E/R Doubling the voltage (E) from 6V to 12V doubles the current (I) for a fixed resistance (R), not halves it. That means you actually need a heavier ground strap switching from 6V to 12V for a fixed value of load Resistance (R), not smaller ground strap. Seems confusing BUT:
A starter motor is Not a fixed value of load resistance (R). The starter current actually decreases in value as it spins due to a counter voltage (EMF) that develops as the starter turns. The faster the starter motor spins, the higher the value of the counter EMF generated. The higher the applied voltage the faster the starter motor spins, the larger the counter EMF, and the lower the DC current draw. Starter current running on 12VDC is lower than the current running on 6V because the starter turns faster operating on 12V and generates more counter EMF that opposes current flow.
thanks Mike...I got it! So the only worry about using a 12 volt battery is the initial kick the starter experiences on the Bendix before CEMF takes effect thereby being a current limiter.