Crimp-on battery cable ends: Have you ever observed the underside of the car’s hood? If yes, you must have seen a web of wiring connections.
Almost 98% of these connections, including battery cables, are crimped and not soldered.
Do you know why?
Let’s discuss crimped connections, focusing on crimp-on battery cable ends.
Table of Contents
- Why is crimping preferred over soldering in battery cable ends?
- How to crimp battery cable ends?
- Conclusion:
Why is crimping preferred over soldering in battery cable ends?
In battery cables and other finely stranded heavy gauge DC cables, there is no place for the solder to flow, and the soldering heat may affect the copper strands tinning (if you use marine-grade tinned copper).
Also, the soldering heat can make the wiring brittle, leading to untimely failure of the wiring connections.
Stranded vs. solid wire
How to crimp battery cable ends?
Follow these steps in sequence to complete the crimping process.
Differ battery cable lugs from battery terminals.
Both of them are capable of forming strong connections between a battery system and battery cables.
The position of posts or studs may differ in batteries, bringing the difference between battery terminals and lugs.
Battery lugs mainly connect the battery cables to the starter port or solenoid, and a battery terminal connects the battery to the battery cables, mostly in marine and auto applications.
Battery lugs are standard in large gauge applications for drawing power or grounding. For battery terminals, you must have two terminals (positive and negative) for a suitable connection.
Types of battery cable lugs:
Copper lugs are preferred. You can make the most secure connection between the battery and cables by soldering or crimping with lugs.
You can get different angle options like straight, right angle, or 45 degrees. And you can have a lot of space with these angled battery lugs.
Apart from copper lugs, people also prefer tinned copper battery lugs. These lugs are the same as standard lugs but have tinned coating.
As a result of coating, there is less corrosion. Like standard copper lugs, you can solder or crimp these lugs also.
Use these tinned lugs if your application is under harsh environmental conditions.
Battery cable lugs
Types of battery terminals:
The most common battery terminals are made from copper. The preference for copper is due to its high conductivity and ability to form reliable and robust connections.
You can find different varieties of battery terminal shapes to suit your applications.
The most versatile copper battery terminal is the straight one. You can either solder or crimp it.
Other than this is a parallel copper battery terminal suitable for unique applications. In the parallel shape, there are two wires.
Right-angled or left-angled copper battery terminals are most handy for cramped spaces.
Battery terminals
Prepare tools and materials required:
- Measuring tape and a marker
- Razor blade or knife to cut installation
- Heat-shrink tubing
- Battery lugs and cables
- Crimping tool (hydraulic one)
- wire cutter
- Heat gun
Process of crimping:
Determine the length of the cable
Firstly, you must plan the points between which you want to run the cable. Remember the cable length that battery lugs take while measuring the distance between these two points.
You can install the lug on the final terminal to hold it in place when you measure the length. From this lug, take the cable and run it to another lug at the first position.
Cut the cable length.
Take a wire cutter and cut the measured length of the cable. Always use high-quality cables to give a fine cut to the wires and cables.
Mark the insulation length for stripping.
Put the wire near the lug so that the wire end is next to the lug portion where it starts tapering.
Mark this point on the wire for the lug length from the flat area to the tapered area. Ensure you do not strip too much insulation, as open copper wires are unsafe.
Also, less stripped length is not good as it can hinder the movement of wire inside the lug, not allowing correct crimp.
Stripping off insulation
Stripping the insulation is difficult; a cable cutter, side cutter, or wire stripper won’t do the job.
Cut only up to ¾ of the insulation depth with a sharp-edged knife. After that, insulation is soft; thus, a regular knife can nick the remaining soft strands.
If you use a sharp knife and nick the copper by chance, it can be a major issue later on, and this mostly happens with cables with small gauges with thin strands.
Separate insulation
As you cut through the insulation, you can just bend the battery wire and strip off the insulation.
If it does not come out this way, touch a knife slightly to the attached rubber strands, and it will come out easily.
Once the insulation is fully separated, remove it by pulling until you see a clean wire up to the marked length.
Put wire into the lug.
Now, you have a lug corresponding to the cable size. Look for any oxidation or any other defect inside the lug.
Use a different lug or clean the lug with sandpaper or a wire brush if you find anything.
Leaving any oxidation may enhance the termination conductivity, resulting in overheating or failure of the connection.
Once cleared, slide the stripped wire end into the lug and see that all exposed portion goes inside the lug, leaving no exposed copper.
Prepare crimper
Hydraulic crimpers come in different die sizes. So, pick one that has the perfect size for AWG wire sizes to give the strongest connections.
Also, these crimpers stamp the die size on the lug after the process.
Once you install the right size dies, check if you have closed the released valve.
Initial crimp
Insert the lug in between the dies. Pump the crimper handle several times to allow the dies to securely hold the lug.
Few lugs are long, and you may need to crimp the lug twice at different points. So, keep the dies near the lug’s open end for its first crimp.
Once you are sure the dies have held the lug firmly, put the wire inside completely, ensuring no copper is left at the lug’s end.
As you crimp, put the pressure continuously until you realize that both the dies have touched each other.
Finish crimping
Now, you can take the pressure off and start crimping at the second point that needs to be crimped.
If you have used the correct dies and tools, you will get a strong crimp connection, and the wire will be firmly held inside the lug.
You must reduce the die size if you notice wire coming from the crimp. On the other hand, if you notice that the crimp side where the two dies meet looks crushed, increase the size of the die.
Once you finish crimping, try to pull the wire out. If it is firm, you are good to go ahead.
Crimp the other end.
You must be careful while crimping the battery cable at the second end. As cables are thick, moving the cable and inserting it into a lug with the wrong orientation is impossible.
You can mark the lug and the wire to determine where to line the cable while crimping the second lug.
Now, align the marks on the lug and the cable and crimp the second lug as you did earlier. Keep in mind every detail that you did with earlier crimps.
Test fit
Test fit the cable and check if the length and rotation are fine. If everything goes well, move on to the next step.
Heat-shrink
For a 4/0 cable, you must use heat shrink tubing in the ratio of 3:1. When flat, the tube is 1 ½” wide.
Take 3-inch tubing for each end. For cables with small diameters, you can use short-length tubing.
It is done for two reasons: reducing cable stress from flexing and preventing moisture entry into the crimp, which may lead to oxidation.
Once you have the right-sized tubing, please insert it into the crimped wire. Start heating the tubing using a heat gun.
It would be good if you use a wide-stripped heat gun so that heat spreads consistently to the complete tubing circumference.
Tinned copper terminal end
Conclusion:
Once you finish this process, you have a firmly crimped battery cable that is perfectly safe to use.
Sometimes, while stripping the insulation, if you cut some wires, the cable does not fit appropriately into the lug, resulting in a loose crimp connection.
Also, not applying complete pressure may result in loose crimp. In addition, incorrect die size also results in weak or loose joints.
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