(Starthilfe-)Kabel löten und/oder crimpen? | Posts 16+

Quote:

OK, that makes sense. Dem kann man aber vorbeugen, indem man nach ein paar kurzen Orgelversuchen vorsichtig fühlt, ob eine Klemme auffällig warm wird, und die dann so oft anders ansetzt, bis sie nicht mehr weiter heizt.

Sometimes there's just not enough time - things have to be done quickly.


When using low-quality jumper cables, it is recommended to let the donor vehicle run for 1-2 minutes before attempting to jump-start the other vehicle, in order to prevent unnecessary power surges.

Bertil wrote:

You've probably just been lucky so far... until one of those cars breaks down on you.

I'll wait and see.

I have just re-soldered the crimps on the jump start cables, and I've attached the measurement data before and after.
Approximately 25 mV of voltage loss from two crimped connections at a 5-ampere test current results in a total voltage loss of 1.25V when considering an assumed 250A load during normal cable operation. This may not seem significant at first and might only appear as a reduction in starter power, but according to the formula P = U * I, a total of 312 watts would be dissipated in the two crimped connections.
With a generous 50:50 distribution, each crimp still consumed 160 watts, but in the worst-case scenario, a single crimp could consume as much as 300 watts.

After soldering, each crimp connection results in a voltage drop of approximately 5 mV at 250 amps, which corresponds to a power loss of 1.25 watts.

So, at least here with these jump start cables, I spontaneously feel that a localized heat development of approximately 300 watts during a factory crimping process is more dangerous in terms of fire hazard than 1.25 watts at the same location...

Okay, I'll admit it, as an electrical engineer, I also sometimes solder crimp connections... but only if they are perfectly crimped using the specified crimping tools, and in my opinion, soldering them is purely for safety, for example, the ground connection of the audio system, etc.

I wasn't aware that this wasn't permitted, although I did know that soldering wire ferrules and crimp connections is prohibited.

Ich habe mir mal die Mühe gemacht, beim Altmetallhändler meines Vertrauens aus einem Gummikabel zwei Stücke á 7 Meter und 50mm² hochflexibel in Schwarz u. Brauto peel it.
I paid something around 10 to 15 euros for it (the price is probably not valid anymore).

The matching pliers are available at Europart. I paid 55 euros for the set of 4. I crimped on ring terminals, soldered them, and it's done.

The pliers can almost be described as requiring a two-handed grip. Between the two massive brass jaws, a braided cable is screwed in, which is typically only found between the engine block and the body.

Functionality: excellent!
For example, two people were struggling to jump-start their cars in the parking lot in front of my store. When I left the store, they were still there. When I asked them if something was wrong, they said they didn't know, and it probably wasn't the jump-start. I then quickly brought over a cable.
After just two turns, the box was on.

Europart has branches, among other locations, in Mannheim and Trier.

Greetings, Cryonix.

ulf wrote:

... I have just re-soldered the crimps on the jump start cables, and I've attached the measurement data before and after. . . .

You've unfortunately bought some extremely cheap, low-quality crimp connectors. A crimp connection should not have that much resistance.
But you have to believe me that soldering weakens the cable over time. I've seen far too much of that nonsense. Especially when it comes to using these cables outdoors (in humid environments).


My 25mm² jump starter cables are at least 28 years old, and despite being crimped, they still work surprisingly well.
Sure, I didn't buy the cheapest, low-quality stuff back then either, but anyone who wants to use such dangerous, cheap crutches has to accept the risks that come with it.

Bertil wrote:

But you have to believe me that soldering weakens the cable permanently. I've seen far too much nonsense about that. Especially when it comes to using these cables outdoors (in humid conditions).

Just now, at the Polo, I measured the factory crimp that was soldered in 2004 on the body side of the thick battery ground cable.
Last: Ignition + Low beam + High beam, total approximately 20 amps.

Voltage drop from stranded wire to soldered ring terminal: 0.0 mV.

Voltage drop of the ring terminal, from crimp area to screw hole: 0.3 mV.

Voltage drop at battery terminal clamps - crimping to wire (not yet soldered because I didn't want to deal with the thermal capacity of the terminal): 1.0 mV.

Voltage drop along the entire length of the strand (~12 cm): 3.4 mV.

This sample demonstrates that the contact resistance of a crimped and soldered connection in the engine compartment, which is approximately 8 years old, can be at least 10 times smaller than that of a factory-crimped original Polk connector.

Quote:

My 25mm² jump starter cable... Sure, I didn't buy the cheapest junk back then either, but whoever wants to work with such dangerous, cheap crutches has to live with the risk.

. . . or, for example, when it comes to Einhell cables, you could solder the crimps and install more robust pliers .

Don't both Bertil and Ulf have a point?

Bertil:
Soldering the ends and then screwing them together (using a wire connector) is bad because the cable can remain flexible for a long time.

Ulf:
Filling already dry, crimped ends with solder shouldn't actually have this disadvantage; instead, it should help to reduce the contact resistance.

"Or, 'Where is my flaw in reasoning?'"

m;

Hello everyone!

Ohne mich hier auch noch groß in Ulf's "Dr.-Arbeit" einmischen zu wollen...
Bertil is probably more right than Ulf, although I personally wouldn't make a big deal out of it if the connection is soldered and not screwed.

The "misconception" lies in the fact that solder ALWAYS has a lower conductivity than copper. Furthermore, the surface of the copper attracts the tin, which would definitely degrade an initially excellent copper cable lug/sleeve contact.
If a large amount of electricity is flowing through something, where will it get hotter?
Und was macht's Lötzinn, wenn's heiß(er) wird, was Cu nicht macht?
...a vicious cycle that will ultimately lead to the situation depicted in Bertil's photo above.

The best connection remains a "gas-tight (!!) crimp" .
If the crimping is already poor, soldering may not always improve the connection. Even if the crimping isn't airtight, oxidation may have formed on the copper and the cable lug (which is invisible from the outside!), and the solder may not make contact or improve the connection in those areas.

Best regards from Munich!

Does tin-plated crimping not provide full surface contact between the cable and the terminal?

Because I don't actually have that when I'm doing a bare crimp, do I?

Hi Martin!

DieselBär30x wrote:

... The "misconception" lies in the fact that solder ALWAYS has a lower conductivity than copper. Furthermore, the surface of the copper attracts the tin, which would definitely worsen an initially excellent copper cable lug/sleeve contact. ...

Either you don't understand my answer, or I don't understand your question .

Assumption: Conductor (stranded) made of copper, cable lug/ferrule made of copper.
If you crimp it like that, you get copper on copper - it's hard to get much better. It's excellently done, and the whole thing is also gas-tight, so no oxidation is possible, and it will last 1000 years .
If the crimping is not gas-tight now, and you add tin, some or all of the fine wires will be coated with it, resulting in a Zn-on-Zn interface, which will have a lower conductivity than a Cu-on-Cu interface.
WHERE will it get hot? WHAT happens next? ...see above.

Best regards from Munich!

EDIT: Or were you trying to say that there's always "air" between the fine wires because they are round? If so: With proper crimping, the pressure is so high that the fine wires become almost "square," thus creating "full contact."

EDIT2: Pictures below to (hopefully) better understand why tin in poor crimping is bad, and lead-free solder is not only good for the job .

I had the second image in mind when I wrote "massively compressed" above. That's not something you can do with a simple crimping tool in your hand.
hg
Herbert.

DieselBär30x wrote:

... Ohne mich hier auch noch groß in Ulf's "Dr.-Arbeit" einmischen zu wollen... Bertil is probably more right than Ulf, although I personally wouldn't make a big deal out of it if the connection is soldered and not screwed. ...

I don't want to dramatize anything; I don't always see things that way myself. I just want to point out that the approach being used here is neither permissible nor good.
Because... thousands of other inexperienced hobbyists are also reading this, and an action like that can quickly backfire if not handled properly.


In Ulf's case, with his "Labbercrimpung," he certainly didn't make things worse.
However, it should be noted that in this case, the crimping was likely very poorly done.

Quote:

Images below for (hopefully) better understanding of why tin in poor crimping is bad, and lead-free solder is not only good for the job.

I was so focused on the details that I missed the bigger picture... I think these images speak louder than words.
Since I always assumed an "ideal" crimping process, it may have led to misunderstandings on the other discussion page.
You're unlikely to find such flimsy (non-gas-tight) connections in a car that would require re-soldering. That's what I meant.
Furthermore, the tin hardens the flexible strands of the cable, which can lead to uncontrolled cable breakage due to vibrations (especially in cars), even far away from the soldering joint.

Most likely, the cables I had custom-made are only crimped and encased in plastic for corrosion protection.

DieselBär30x wrote:

If the crimping is not gas-tight now, and you add tin, some or all of the fine wires will be coated with it, and you will end up with a Zn-on-Zn interface, which has a poorer conductivity than a Cu-on-Cu interface.

Zn can only flow into areas where there was no previous Cu-Cu contact.
In other words, existing copper-to-copper contact areas are NOT replaced by zinc, but the total contact area is increased, and the transition resistance between the cable and the crimp connector decreases accordingly, which suggests that resoldering might be a viable option.

However, with proper crimping using finely stranded wires that are pressed "squarely," there is no room for this to occur, meaning the transition resistance between the cable and the crimp connector cannot change significantly (except for the parallel tinning at the edges of the crimp connector).

Isn't it the case that the thermal expansion of tin is different (greater) than that of copper?
That is to say, the crimped combination of the copper sleeve and the copper/tin core will gradually become loose over time.
hg
Herbert.

ulf wrote:

Zn can only flow to areas where there was no previous contact between Cu and Cu.

With a perfect crimp, there is no space. So, the solder is barely sitting on top, nothing more.
You won't achieve a significant improvement in reach with that.

Quote:

In other words, existing copper-to-copper contact areas are NOT replaced by zinc, but the total contact area is increased, and the transition resistance between the cable and the crimp connector decreases accordingly, which suggests that resoldering might be a viable option.

Okay, so how do you solder the zinc?
Zn is zinc!!!!

I'm therefore going to assume it's Sn (tin) .
Okay, I'm ready. Please provide the German text you want me to translate.
With significantly worse contact resistance and the undesirable effects caused by the material used, this is definitely not the case!


Here's a brief introduction to soldering materials:

I'm assuming we're talking about "standard" soft solder for electronics applications.
This typically consists of about 60% Sn (not Zn ) and around 40% lead (Pb). It also includes a highly corrosive substance, such as flux, including rosin. Without it, the soldering process will not work, as the oxide layer on the copper virtually prevents soldering. This layer must be "broken" using flux. In doing so, you are already damaging the protected copper surface to make it more amenable to soldering.It's a shame, but now tin and lead will be applied and cover it all again... Unfortunately, not completely. You would have to completely wash away the flux, which means there will be large areas where no solder has been applied at all. This leaves a lot of exposed copper, making it vulnerable to moisture.
In addition, Cu, Sn, and Pb also exhibit a significant potential difference in the electrochemical series (approximately 0.5V), and the addition of moisture (which is always to be expected in a vehicle) creates a small battery. This process is gradual, and depending on the environment, the entire system can slowly decompose into a white, blooming landscape.

While other types of solder exist (containing silver, antimony, bismuth, or gold), they are difficult for hobbyists to work with due to the high processing effort required or because they are extremely toxic.

Unfortunately, soldering copper with a Sn/Pb solder for use in a humid environment is not a good idea.
Even though I sometimes do it myself, I am fully aware of this "crutch" and its dangers.