How To: Safe, Reliable Electrical Crimp Connections (part 2 of 2)

in Part 1 we introduced the topic and assembled our tools. This time, we’ll use them to make something and show how its done, step by step.

So after having gone through Part 1, we assembled our gear and have what we need to get a job done.

What are we going to do? I have an article on how to create an ultra reliable ebike battery charger (which also works as an AC charging brick for a solar generator like a Bluetti AC200P). Since I have an extra one sitting and gathering dust, we’ll make some plugs for it here. That will serve the dual purpose of giving readers of that other article a step-by-step construction guide.

What do we need to get the job done?

Everything we saw listed in Part 1. Our project device will be a Mean Well HLG320H-54A LED power supply.

The Mean Well power supply with bare wires. If purchased new retail, both ends will be stripped and tinned.

We will also need a 6-foot-long, 3-prong AC power cord with an open pigtail on the female side. Never seen one before? Don’t worry they are commonly available. Apparently a lot of construction workers tear up the cords on their power tools, so replacements are easy to find and cheap.

Lets get started.

Step 1

Size the heat shrink you will need at the very end of this process, and run it down along the wire NOW before you need it. I cannot even begin to count the number of times I have gotten wrapped up in making a cable and then realized I forgot to size and place the heatshrink for that last step. Do it now before you need to do it and before a connector is on and its too late.

The heat shrink has been added – nice and long – and you can slide it well back from the connection as needed.

Put it on the side that you can slide the furthest away from the heat gun for when we have to take that step later. You don’t want to be shrinking this one up when its out of position so it needs to be away from the heat.

Step 2

The wires on the pigtail side of the power cord are already stripped and tinned so they are easy to work with. Lets use those to teach ourselves how deep the butt end connectors are. We can trim these wires so their insulation fits right up to the edge of the metal connector insert. Once we do that, we’ll know how much we need to strip off the wires on the other side of this connection.

Dip the wire into the connector. The insulation on your wire should seat against the metal butt end connector inside. How much extra is there? Snip some off so the insulation fits right up to the end. Repeat for all three wires on the power cord.

Step 3

Next, we strip the wires that go into the other end of these butt-end connectors. The lengths we snipped down to in Step 2 give us an easy visual guide to how much we need to strip back on these wires.

A note on wire stripping: There can be a little more to it than just picking the hole that matches your wire gauge and biting in. I like to spend a little more time on the job so I don’t lose a single wire in the bundle (if I can help it).

Here’s the way I did this particular wire: I picked the 18 ga slot and was able to clamp down hard on it without damaging the wire underneath the insulation. Its a size up from where I’d get a clean, complete cut, and gave me a safe cut of maybe 80% of the insulation. Then I shifted down a size to the 20 ga slot and – very gently, clamped down on the same spot. Just a bit. While slowly spinning the cutters radially around the wire (again, just a bit). This cut the insulation without cutting any of the wires underneath. Until you get a feel for it, put the wire into a hole thats too big for it and work your way to smaller holes from there.

From there, I hand twisted the now-exposed wires so they bunch together and I’m ready for the next step.

Step 4

Crimp connectors onto the wires on the power cord. For this article I am using my new handy-dandy semi-auto crimping tool for the first time, rather than my manual commercial-grade crimper (i.e. giant pliers). The ‘semi-automatic’ part of this crimper is you just squeeze until the crimper releases, and you have a good crimp that is solid, and uniform with every other crimp you make for this job. Because of the small wire size, we can use the pink 18-22 gauge connectors.

Something to remember when you do this: While you are fumbling around the wire can slip partially or even fully out of the connector. Because of this I like to grab onto the connector with my crimper – without squishing it any just yet. Once I have it fixed in place, I use one hand to push and hold the wire end into the connector so it can’t slip back. Only then do I squeeze the bejesus out of it to make the final crimp and permanently connect the two wires.

Step 4 Complete. The semi-auto style crimper with its dual crimps was almost too big for this small 18-22 gauge connector.

Another something to remember: When doing one of these 3-wire connections, things can get awfully tight when you start finishing the connections in the next step. There may not be enough room to stuff the crimper’s jaws in between the wires to get the job done. Solve this problem by stripping enough of the plastic sheathing back from each side so you have enough open space to work with when things start getting crowded. If you can’t do that (I couldn’t here) then you’ll have extra effort in store trying to get the crimper’s jaws in the right spot while the wire stays in place inside the connector before the crimp.

Step 5

Now crimp on the wires on the other side – the charger side. This time, you have to pay close attention to which wire goes where. Since I live in the USA, our power cords do not adhere to the international standard for wiring colors. Connect:

  • The green wire on the cord to the green wire on the charger (GND)
  • The black wire on the cord to the brown wire on the charger (AC+)
  • The white wire on the cord to the blue wire on the charger (AC-)
Step 5 complete. Note the dual crimp lines on each side. The 18-22 ga crimper jaws were almost too large for this connector. You have to go right to the edge of the metal connector inside.

If you live pretty much anywhere else besides the USA, the wire colors will all match and what you connect to what will be obvious.

If you happen to screw up making one of these connections: Bite the bullet. There’s no uncrimping one of these. You have to snip off any crimped connectors at their very edge. Then snip down any wires you haven’t connected yet so they are all still the same length. Then re-strip and try again from scratch.

Step 6

Now you heat shrink the individual wire connectors. Remember the big heat shrink you put over the wire in Step 1? Make SURE you keep it well away from the heat gun while doing this. Let it get warm in the slightest and it’ll stick itself to wherever it is now, and not where you want it to eventually be.

I use my heat gun on its lowest setting, which is much slower going, but it lets me very carefully heat up my connector. I like to push the wires – and the connections – together a little, which spreads them out more or less evenly. Then I slowly rotate them around under the heat so every side of each connection gets heated up. You’ll be able to tell when you are done on each side because you will see a little bit of the internal adhesive squeeze out and form a bead on the wire. When you can see that – AND the air bubbles inside the connector disappear (this is another reason you slowly rotate while heating) you are done.

Ready to begin Step 6

Heat up each END of the connector. Stay clear of heating the center over the metal connector. That center section is where you stressed the adhesive covering by smashing the hell out of it with your crimper. If that stressed area shrinks and tears, it will expose the metal underneath, and thats a bad thing. Let the center section shrink down thanks to the indirect heat coming to it from each of the two ends. Also, if you use a manual crimper, which is much more likely to cause a tear if you are a little overzealous, then staying away from the center will let the adhesive inside liquefy and seal up the hole you created rather than spreading it open via shrinkage.

Step 7

Let the wires cool a bit. Our next step is to slide the oversized, overly long piece of adhesive heat shrink over the connection we just made. If you try and slide it over while the connectors and wires are still hot… it’ll stick to them, shrink up a touch … and you’re screwed. So walk away for five minutes and be patient.

On this power cord, I am using an extra long piece as I want this to be a strong connection. I am also using an oversized tube that will just barely shrink down to hug the power cord, which means it will be very thick once it gets to its minimum diameter. I did this because this cord is going to take abuse as its going to be pulled, coiled and stepped on. Hopefully for years (it turns out when this stuff cools after shrinking its also completely rigid, which is a good thing for protecting my connection).

Step 7 complete. That little red ring of heatshrink near the plug is just a test I did to make sure the big size I used would shrink all the way down to hug the cord.

Application of heat is the same process as it is for working the connectors. Regardless of whether or not it looks like the heat shrink has shrunk down enough to do its job, take the extra time to apply heat to the every angle of the exterior of the strip. Slowly go around all of it in even, top-to-bottom strokes. It may look like its fine halfway thru the process, but going around it and heating thoroughly it at every angle will shrink it down tight on top of the other work you just did.

And… pay attention. Keep the nozzle moving and keep it on low heat. Its a whole lot easier to melt your cord than it is to unmelt it.

And thats the end of the AC cord input side.

The Power Output Side…

We did the power input cord in step-by-step detail. We won’t need to go into that same level of detail on the output side, since its almost the identical process. But there are a couple items worth calling out.

We need step-down connectors this time

The XT60 we are using for power output is a nice beefy 12 gauge, which would need a yellow connector. The Mean Well’s power wires are 14 gauge. Thats ordinarily a blue connector. So we need a step-down (yes, I could have used a 14 gauge XT60 – I do have them in my shop – but I prefer the heavier wire).

We do the same trimming to size the wire in the connector as before. However the 12 ga wires on the XT60 have enough fudge in the 10-ga-capable wire connectors that we can leave the tinned ends on. So no need to snip them, we just take some insulation off and job done. If you can leave the ends of a wire tinned, do it and make your life easier.

Bigger connectors = more room to work with

On the 18-22ga pink connectors, we almost didn’t have enough room to work with. But with the larger yellow 10-12ga connectors that wasn’t a problem.

You can see how the crimping jaws are within the borders of the metal segment on this larger connector; ending fully to the left of the slot in the middle. Lots of room.
The connectors, after applying heat to shrink them down onto the wiring, just before having the external sheath shrunk down over them. They essentially glue themselves and the wire connection together, providing a second of three layers of stabilization to the connection.
The finished product. I used red heatshrink over the wire on the output side simply so my stock of heatshrink (red and black) gets used up at about the same rate.

Author: m@Robertson

I'm responsible for the day-to-day operations at my place of business: Leland-West Insurance Brokers, Inc. We do classic and exotic car insurance all across these United States. I'm also an avid auto enthusiast, a born again cyclist (i.e. an ebiker) and participate in medium and long range CMP and NRA sanctioned rifle competitions.

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