How to Crimp Lug Terminals Onto Copper Wire (With Video)

Lug terminals are integral to any electrical system, facilitating the connection between wires and components like batteries and fuses. Crimping a copper lug onto the wire isn’t tricky, but learning the correct process and using the right tools to get a robust and solid crimp is essential.

This post covers what you’ll need to know about lug terminals and how to create a firm crimp onto your wires that won’t fall out over time. We’ll include:

• How lug terminals are sized
• Recommended lugs and tools
• A 7-step lug crimping tutorial with pictures

Disclosure: As an Amazon Associate, this site earns from qualifying purchases. Though we may earn a commission, the price you pay always remains the same.

Sizing a Lug Terminal

Learning how lug terminals are sized is essential before you crimp one. If you select the wrong size lug for your wire, you’ll create an improper crimp that may crack and become loose over time. The image below shows how the lug’s structure can be compromised when it is crimped over a wire that is too small (caused by too much empty void).

Every lug is designed for two size specifications:

1. Ring size: This is the diameter of the ring hole on the head of the lug. It should correspond to the terminal post size on the component the lug will attach to.
2. Wire size (AWG): Each lug has a neck that only accepts one wire size. You want to make sure that the neck size matches your wire size.

Looking carefully, you can see the lug’s size (2/0 AWG wire size and 3/8″ ring size) stamped just below the ring hole. Based on this information, you know that this lug is designed to crimp over 2/0 AWG wires and fit over 3/8″ terminal posts.

Required Materials

Recommended Lug Terminals

The construction quality of the lug terminal matters. With cheap, non-branded lugs, you risk getting a terminal made with thinner metal, which is dangerous since a thinner lug cannot transmit as much electrical current.

When buying lugs for thick battery cables that handle high levels of electrical current, we recommend going with an established brand like Wirefy, which is based in the USA. Using 100% thick, annealed copper, we use Wirefy lugs in our camper van’s electrical system and are happy with the quality.

If your electrical project involves many different-sized wires (e.g., 2 AWG to 8 AWG), buying an assorted lug size set can help you reduce waste and save money. The set below helped us install our solar, inverter, and DC-DC charger systems, which all used different-sized wires and required different-sized lugs.

Recommended Tools

Properly crimping a lug terminal onto a wire end involves more than just the crimping tool. You’ll need additional items to cut the wire, strip off the outer insulation jacket, and apply heat shrink over the lug and wire. To accomplish all this, we recommend the four tools below. We use these same tools in our video, posted at the beginning of this article.

Hydraulic Crimper vs. Hammer Crimper

You can use a hydraulic or hammer crimper to fix the lug onto the wire. We have experience using both tools, and the hydraulic crimper is the best option.

The hydraulic crimper is more expensive but always produces solid and consistent lug crimps. It is hard to make a mistake with this tool. With the hammer crimper, user-related errors are more likely (e.g., how hard and how many times you stick the anvil). This can result in crimps that are too strong or too weak.

	Hydraulic Crimper	Hammer Crimper
Cost	More expensive	Cheaper
Ease of use	Easy & consistent	Error-prone
Crimp quality	Always high quality	Quality depends
Resale value	Yes (we sold ours)	Not really?
Which we prefer?	Yes!

Lastly, think about the tool’s resale value. The hydraulic crimping set still retains second-hand value when you’re done using it. A used and dented hammer crimper? Not so much. There isn’t much of a price difference between the two tools when factoring in the money you get back from selling the hydraulic crimper.

On a budget? If you don’t want to spend money and have a screwdriver, follow this post. Good luck!

How To Crimp A Lug Terminal Onto Wire (7 Steps)

Follow our seven-step tutorial below to ensure your lugs are properly crimped onto the electrical wire.

Step 1: Measure Wire Length

Electrical wire isn’t cheap, so ensure you have the correct wire length to connect your two components.

To do this, measure the distance between the components you want to connect with your wire. In the below example, we use a ruler to measure the distance between a fuse and a battery switch, which is about 4”.

Lug heads are ~1” long. So, subtract 2” (two lug heads) from the total wire length when measuring. In our example, we only need a wire length of 2”.

Step 2: Cut the Wire

Once you know the length of wire you need, cut it with a wire cutter. We recommend the Klein Tools wire cutter if you are cutting a maximum of 2/0 AWG wire gauge.

Step 3: Mark and Strip Off Jacket Insulation

You must strip off part of the insulation jacket to expose the bare metal conductors, which will then be inserted into the lug. But before you strip off the insulation, you should measure and mark the cut line with a pen.

If you strip off too much insulation, the copper conductors will be exposed past the lug, posing a fire hazard. If you strip off too little insulation, you won’t be able to insert enough of the wire into the lug.

To measure the ideal length of insulation to strip off, place the wire next to the lug’s neck and use a pen to mark the insulation right where the lug reaches the neck’s opening. For most lugs, the appropriate length to cut is ~7/8”.

Next, cut along the pen markings with a box cutter and peel off the jacket. Be sure not to cut too deep or risk severing the thin individual metal strands.

Step 4: Crimp Lug Onto the Wire

Insert the wire into the lug. Ensure EVERY conductor strand is inside the lug’s neck and no frayed strands are left out.

Next, place the lug’s neck into the hydraulic crimper’s crimp dye and continue to compress the handlebars until the two crimp dyes meet. We recommend watching our video tutorial to see how this works.

Crimp dye sizing: If using copper wires with a high strand count, we learned that the appropriate crimp dye size is one size smaller than what is listed. For example, if you have 2/0 AWG stranded wire, select the 1/0 AWG crimp die. Stranded wires compress more than solid wire, so using a smaller crimp dye is more appropriate.

Step 5: Test Crimp Strength for Pull-Out Resistance

When the crimp is complete, test the crimp strength by pulling the lug away from the wire. If the lug slides off easily, throw it away and repeat with a new one. (With our hydraulic crimper, this has never happened to us.)

Use a reasonable amount of force, but don’t overdue. You don’t need to be Superman or Hulk for this tensile test. However, if following pull-out strength standards is essential, refer to the American Boat and Yacht Council code ABYC E-09 (page 37) for a list of appropriate tensile forces for each wire gauge.

Step 6: Place Heat Shrink Over the Lug & Use a Heat Gun

The lug is crimped over the wire, but the job is not yet completed. You want to protect and insulate the connection point between the wire and lug with a heat shrink sleeve.

Our recommended wire lugs come with pre-sized red and black heat shrink sleeves. Place one of the sleeves over the wire and ensure it sufficiently covers the wire and the lug’s neck. Once in place, use a heat gun to activate the heat shrink and adhere the sleeve over the wire/lug joint.

Step 7: Repeat the Process for the Other Side

Congratulations! You’ve just completed the first of many lug crimps for your electrical system. Now, get ready to begin the process again for the wire end on the opposite side.

FAQ

Conclusion

Learning to crimp lugs onto electrical wire is crucial when building any electrical system. Remember, the most important reason to get good, strong crimps is for your safety. You don’t want the bare metal wire to eventually work its way out of the lug and become a short circuit hazard, which can cause a fire.

But if you follow our lug crimping tutorial and use the proper tools, we’re confident your lug connections will keep you safe. Please let us know in the comments section below if you have any questions.

For more DIY camper van information, visit our van conversion guide.

Happy building!