Having issue with crimping lugs on 50 and 35 mm cables, apart from crimping ferrules on 230 V cables the big stuff is new to me. I borrowed a crimper from a friend and I had difficult using it because handles were short so I bought my own which had longer handles and would do bigger cables in future. When I crimped 50mm cables I had really good neat result and cut through a sample and could see no gaps and it looked like a solid core of copper. When I did the 35 mm the crimp was loose and would pull off so set crimper to 25mm which worked but made the whole crimp look a bit of a mess. This was on my new crimper. I then did a crimp on the borrowed crimper and that was the same lug not crimped. So to my mind the cable or ferrule not to spec.
After doing the 35 mm crimp I set to 25mm crimp and squeezed just part of the way so as not to distort the terminal. Is what I am experiencing to be expected? I am now questioning how secure the 50 mm crimps are.
When crimping a lug, itâs obviously important that the cable and lug match in diameter.
In addition, a brand may have lug models for stranded cable with multiple twisted solid cores, and lugs for fully flexible cable with many fine cores.
I work with Klauke Dynamic lugs and Dynamic hexagonal inserts in a cordless crimping tool.
The Klauke Dynamic series is suitable for all types of cables.
Good cable, thick lug (wall), correct fit, repeatable process, pull test and thermal inspection at ultimate load. I have seen and repaired so many crimps that I am seriously considering an electric/hydraulic crimper for the next project.
I have found that quite a few of the Cheap Hydraulic crimpers have dies that are not the correct size. I would bet that is where the problem lies. I only use Cembre crimps so I know thatâs not the problem.
I have two sets on my shelf that are destined for recycling because unlike the others I couldnât return them and I have reverted to my old BICC manual crimpers.
Indeed, just disregard whatâs stated on the dies, take the set that fits. I also like the big stationary âpunchâ crimpers but canât carry those around to customers.
Oh not to forget: never solder !
Same problem. I eventually bought a portable hydraulic crimper like the one pictured above. As per Theoâs reply I use the die that fits. What I have found is that depending where you buy the lugs they can have different wall thicknesses and this affects the fit in the die when it crimps.
Thank you all for your replies. Judging from the response to this subject quality crimping seems to be of quite some concern. In the end I settled for 35 mm crimp followed by partial 25mm crimp stopping before commencemend of any distortion. That seems to give a satisfactory crimp. Interestingly the red cable gave me the most grief black in the same CSA did not need as much attention. I used a caliper to compare the stripped conducters and could see no size difference beetween red and black. I jibbed at measuring the individual fine strand probably would not be accurate, in order to check if cable was not as described, The lugs were from a reputable electrical outlet and from the same delivery.
Yeah we have on more than one occasion have modified dies for crimpers.
Also for some reason some lug brands available on the market have thinner walls.
One of the other installers has a shimm they ues when they see crimps arenât quite where they should be. You definitely gotta pay attention.
The topic absolutely hits a nerve 
A good crimp will cold weld the copper wire and lug:
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Just watched some of the videos recommended in the replies. When I was setting up to find best way to crimp I only saw single crimp made on a lug. One of the videos did 2 another about 4. The other thing I noted the lugs seemed to be thicker than what I had bought and what my friend had, but then the Americans donât do things by half and probably manufacture them whilst we end up with cheap imports. The crimpers using dies in a hydraulic system give a wider crimp so guess they are the better option.
In my working life I must have crimped many thousands of lugs, We always used Cembre lugs and crimp tools.
I still use Cembre lugs but cant afford their crimp tool.
They are worth the extra cost
My experience is that for 35 / 50mm itâs mostly the ferrules or cables fault and not the tool.
Both, cables and ferrules are sold worldwide as either mm or AWG ratings. But the AWG rating is physically a bit smaller:
50mm² ~ AWG 1 = 42.4 mm²
Now, depending on what the cable manufacturer and ferrule manufacturer uses as basis for production, you may have a 50mm² cable and a 42.4mm² ferrule - that will be tight. May also be the otherway round, so a 42.4mm² cable and a 50mm² ferrule will feel lose.
crimp chart.pdf (375.2 KB)
start with quality connectors, in the US ones that are UL listed and come with data sheets see example attached.
if the connector you have or are looking at getting does not have a data sheet do not use/buy it.
data sheets will show what size and type of wire a connector can take along with tool and die that should be used.
you should also be using listed wire a known type that is shown on the data sheet.
for a listed connector they are tested with each die shown on data sheet, not all dies are equal so use only listed dies.
number and location of crimps will also be listed be sure to follow that.
there are many opinions but you should follow manufactures instructions / data sheets for the connectors you select. (if there isnât a data sheet you are guessing)
my opinion avoid indent tools for fine stranded wire, unless it is listed for that use on the data sheet.
make sure your connectors and wire are clean, 99% alcohol
I used an hydraulic crimp tool (12 ton) with long lugs ( you can crimp them over a length of about two cm in two operations) and the correct set of bits matching the wire gauge. In addition I solder the crimps afterwards with a 300w solder iron, to ensure an optimal (low) contact resistance. I use 70mm2 double-isolated high-temperature cable. I consider it essential that the cable losses are minimal, since higher cable resistance (including contact resistances) will reduce the cable temperature and the power losses under heavy load.
Regarding the difficulty to connect 70mm2 cables on the inverter, I used super flex (double-isolated, high temperature cable). A bit more expensive, but industrial quality.
This is, to my best knowledge, a mortal sin in manufacturing cables. A) a correct crimp guarantees a cold welded connection that cannot be improved upon by soldering. B) Soldering may serve to hide bad crimps and worse, introduces new mechanical failure modes due to local hardening of the wire strands outside of the lug.
I disagree. Only the tip of the over 900 strands is soldered. Itâs not a question of hiding bad crimps at all (I made these cables for my own system). I use long industrial quality lugs with a 12 ton compression over a length of over 2 cm. You have no guarantee that the pressure between the many hundreds of strings in a superflex cable fuses the strands evenly providing a stable, low transfer resistance on the long term when oxidation might occur. It maximizes the contact surface between the strands of the cable and the lugs. Of course you canât use it with cheap plastic battery cables.
I purchased a 12 tonne hydraulic hand crimper which did a perfect job, however after a couple 70mm crimps, I then purchased a 12v hydraulic crimper.
For the slightly extra cost it is a far more efficient and effective tool.
I found that the size of the die bears little relation to the cable size in mm² of the cable terminal.
The die size is selected to suit, not to the mm² of the cable or terminal.
Then the crimp is bad.
Here are the pros and cons of adding solder after a good crimp:
Pros (potential benefits, though often minor or situational)
- Can provide extra protection against corrosion / oxidation by sealing the end of the lug/barrel (especially useful in marine, outdoor, or high-humidity environments if no heat-shrink is used).
- May fill small voids or imperfections in a suboptimal crimp, slightly improving contact area and reducing the chance of micro-movement (some people do this on high-current battery cables for peace of mind).
- Gives a visual confirmation that the wire is fully inserted and âlocked inâ (subjective benefit).
- In very high-current applications (>50â100 A), some believe it adds marginal conductivity insurance.
Cons (why it is advise against)
- Wicks up the stranded wire: Solder travels up the strands (wicking), turning a flexible multi-strand cable into a rigid solid one for several millimeters to centimeters beyond the crimp.
- This creates a stress concentration point right at the crimp exit, making the wire far more likely to break from vibration, flexing, movement, or thermal cycling. This is one of the most cited failure modes in automotive, marine, and mobile applications.
- Makes the joint brittle overall: A good crimp is gas-tight and cold-welds the strands together under huge pressure. Adding solder introduces a brittle intermetallic zone that can crack under mechanical stress or thermal expansion/contraction.
- Can hide a bad crimp: If the crimp was poor (loose, strands not fully captured, wrong tool/die), solder may flow in and mask the problem temporarily, until vibration or time causes failure. A proper crimp doesnât need this âhelp.â
- Risk of overheating / insulation damage. Soldering a lug thatâs already crimped often requires more heat (large thermal mass), which can melt nearby insulation, weaken the wire further, or create hot spots.
- Creates voids, flux residue, or contamination. Poor soldering technique can leave flux pockets or air voids inside the barrel that trap moisture and promote long-term corrosion, worse than a clean dry crimp.
- Reduces vibration resistance: Crimped-only connections are superior in high-vibration environments (cars, aircraft, machinery, etc.). Soldered joints (or crimp+solder) fail faster under shake tests.
- Against manufacturer recommendations and standards â Most lug/terminal manufacturers (e.g., for Anderson, Molex, aircraft-grade terminals, automotive) and standards (MIL, IPC, ABYC for marine, etc.) specify crimp only or solder only, not both. Combining them often voids any implied reliability.
Bottom line / best practice
- With the correct crimping tool (with the right die for that lug size) and technique: just crimp, itâs faster, more reliable in most real-world conditions, and is the preferred method.
- Then seal with adhesive-lined heat-shrink tubing (with or without a small amount of dielectric grease inside) for corrosion protection, this is almost always better than solder.
- Only consider crimp + solder in very specific cases (static/high-current/low-vibration setups), and even then itâs considered unnecessary or harmful.
If youâre not confident in your crimps, improve your crimping technique/tools rather than trying to âfixâ it with solder.
In short: soldering after a good crimp does more harm than good. A proper crimp alone is the strongest, most reliable option.