How to Crimp Solar Panel Connectors

Connecting solar panels together properly is a crucial part of any solar power system installation. Choosing the right connectors and crimping them correctly ensures proper conductivity between panels and prevents loose connections or shorts that could lead to system issues or even fires.

Crimping may seem intimidating, but with the right tools and a bit of practice, anyone can learn to reliably crimp solar connectors. This guide will walk through everything you need to know about crimping solar panel connectors, from understanding the different types of connectors to step-by-step instructions for making proper crimps.

Why Proper Crimping Matters

A loose or faulty crimp on a solar connector can cause power loss and other issues like:

• Increased resistance and heat generation at the connection point
• Intermittent continuity or total failure of the circuit
• Accelerated corrosion due to moisture and contaminants entering the connection
• Risk of sparks, arcs, and fires from high resistance points

Even a small amount of increased resistance in the crimp, say 0.01 ohms, can add up to a substantial amount of power and efficiency loss over an entire string of solar panels. Properly crimped connections ensure low resistance and protect against all of these potential problems.

Choosing the Right Connectors

There are a few different types of connectors commonly used for solar panels, with MC4 connectors being the most popular for small to mid-size residential and commercial systems.

MC4 Connectors

MC4 connectors are small, snap-together connectors that are polarity-specific and IP67 rated for waterproofing. The housings are made of UV-resistant polyamide and the contacts plated in tin, copper or silver. They have a maximum current rating around 30A and voltage rating of 1000V DC.

MC4 connectors come in three wire size versions – 2.5mm2, 4mm2 and 6mm2 for compatibility with different wire gauges. They’re used for both connecting panels together in series and paralleling strings of panels.

Amphenol H4 Connectors

Similar to MC4s, H4 connectors are compact, snap-together and polarity-specific. The biggest difference is they utilize screw-machined aluminum housings rather than plastic. This makes them a bit more rugged for harsh environments.

Tyco Solarlok Connectors

Solarlok connectors feature a sturdier metallic housing and spring-clamp terminals instead of crimped connections. They’re easy to install but more expensive than crimp options.

For most residential and commercial installs, MC4 connectors are the best option for their affordability, small size and simple crimp method.

Necessary Tools and Materials

Crimping solar connectors requires just a few important tools and materials:

Crimping Tool

A good quality crimping tool designed for solar connectors is by far the most critical component (Figure 1). Don’t attempt to use a generic pliers or crimper – the special hexagonal indents are sized specifically for solar connector terminals.

Figure 1 – MC4 crimping tool example

Manual and hydraulic versions are available. Manual crimpers are perfectly suitable for most applications and you can find high quality ones starting around $40. Hydraulic makes more sense for large solar farms doing huge volumes of connectors.

The tool must be matched to the wire size – e.g. 2.5mm2, 4mm2 or 6mm2. For a residential system, a 4mm2 crimper will typically work for all the connectors.

Connectors and Terminals

You’ll need the proper connectors and copper crimp terminals for the wire size you’re working with (Figure 2). Always stick with reputable brands like Amphenol, Staubli, TE Connectivity for quality and reliability.

Figure 2 – MC4 connector components

It’s a good idea to keep extra male and female connectors and terminals on hand since they’re cheap. You’ll almost certainly need to re-do at least a few crimps, especially when starting out.

Wire Strippers

A simple set of wire strippers is required to strip back the insulation on the cables to insert into the crimp terminals (Figure 3). Make sure they’re sized for the wire gauge you’re using.

Figure 3 – Wire strippers

Cable Cutters

A set of diagonal cutters is handy for cleanly cutting the cable to length before stripping and crimping on the terminals (Figure 4).

Figure 4 – Diagonal cutters

Multimeter (Optional)

A multimeter allows testing of the conductivity through the crimped connectors and verifying a low resistance connection. Not strictly necessary but handy for troubleshooting.

Safety Equipment

Safety glasses for eye protection and gloves for handling the connectors are recommended.

Step-by-Step Crimping Process

With the right tools in hand, you’re ready to start crimping. Follow these steps to properly crimp solar panel connectors:

1. Cut the cable

If working with new bulk cable, cut it to the required length using diagonal cutters. Leave an extra 15cm or so initially to allow room for mistakes.

2. Strip the insulation

Strip back the outer insulation about 7mm using the wire strippers. Take care not to nick the inner conductor.

3. Insert into terminal

Fully insert the stripped conductor into the crimp terminal ensuring no copper strands stick out.

4. Crimp the terminal

Place the terminal inside the appropriate hexagonal nest of the crimper. Ensure it’s fully seated at the base of the indent. Apply full and even pressure to crimp the terminal down onto the wire.

5. Trim excess wire

Use the diagonal cutters to trim away any excess conductor flush with the crimped terminal.

6. Insert terminal into the connector

Fully insert the crimped terminal into the open side of the connector body until it clicks into place. Give a light tug test to ensure it’s firmly attached.

7. Repeat the process on the other side

Repeat steps 1 through 6 for the other side of the connector. It’s critical to maintain proper polarity by using a male terminal on one side and female on the other.

8. Join connectors

Finally, join the two connector halves together firmly. You should feel and hear a clear snap as they interlock. Again, double check you have proper polarity matched.

9. Test connection

At this point it’s a good idea to test continuity across the connector if you have a multimeter. You’re looking for a very low resistance reading to confirm it’s a good connection.

If the resistance is higher than expected, it likely means there’s a poor crimp. Cut off the bad connectors and re-do it. With a little practice you’ll get a good feel for proper crimps.

Crimping Problems and Solutions

Even with the right tools, it’s easy to make some mistakes when you’re learning to crimp connectors. Here are some common problems and how to avoid them:

Insulation Crimped Into Terminal

This happens if you don’t strip back enough insulation before inserting the wire into the terminal. Use the strippers to take off another 1-2mm and re-crimp.

Conductor Strands Visible or Sticking Out

If you see strands protruding outside the crimped area, the wire wasn’t fully inserted into the terminal. Cut it off and re-insert the wire all the way in before re-crimping.

Weak or Incomplete Crimp

Check that you’re using a properly sized crimper and applying even pressure. Re-crimp the terminal and also check it’s aligned squarely in the crimper nest.

Crimped Terminal Falls Out of Connector

Make sure you fully insert the terminal into the connector body until it clicks securely in place. Wiggle test it after crimping to confirm it won’t pull out.

No Continuity or High Resistance

Either the wire or terminal was not fully inserted before crimping. Trim back the wire, re-crimp and re-test for conductivity.

Helpful Crimping Tips

Follow these tips when crimping to avoid mistakes and get consistently solid connections:

• Always use the properly sized tool, terminals and connectors matched to the cable wire gauge.
• Keep the crimped terminals perfectly oriented as you insert them into connector body.
• Insertion takes a good amount of force – push hard until you hear and feel the terminal click into place.
• Pull on the wire after crimping to verify a strong connection. Wiggle the connector to confirm the terminal is locked in.
• Limit the number of re-crimps on a given terminal and wire. No more than 2-3 times max before cutting off any flattened or damaged sections.
• Set up a clean workspace with good lighting. Keep things organized to prevent mixups.
• Stay focused while crimping and don’t rush through the repetitive process. Mistakes happen when you get complacent.
• Test your crimps often, especially if doing large volumes or moving to a larger wire gauge.

Crimping Different Wire Sizes

The same basic crimping process applies for all solar wire sizes, but there are a few key differences:

2.5 mm2 Wire

• Used for small gauge wiring up to about 5 amp circuits
• Terminal goes into connector body diagonally
• More precise stripping and crimping required due to small size

4 mm2 Wire

• The most common size used for solar arrays
• Terminal inserts straight into connector body
• Requires a bit more force to insert terminal and join connectors

6 mm2 Wire

• For higher ampacity main conductor runs like array home runs
• Larger stripped section and terminal
• Very firm crimping pressure and insertion force required

The key is using the exactly matched wire gauge crimper and components. Don’t try to crimp a 6mm2 wire in a 4mm2 tool – it simply won’t make a proper connection.

Solar Panel Wiring Configurations

Understanding basic solar wiring architecture helps ensure you’re crimping connectors in a way that makes sense for the system design. Here are a few common solar panel wiring setups:

Parallel Wiring

Cable coming from the charge controller connects in parallel to each panel or panel string . This strings the panels together into an array.

Parallel wiring is done by connecting the charge controller wiring to one side of an MC4 connector and panel wiring to the other side.

Series Wiring

Panels are daisy chained together in series by connecting the positive lead of one panel to the negative lead of the next using MC4 connectors .

Series wiring increases the voltage output of the overall string to match the battery bank, grid-tied inverter or other system connectivity.

Combination Wiring

Often a combination of series and parallel wiring is employed. Panels are connected in series into long strings, then those strings paralleled together.

This builds up to higher system voltage and wattage for larger solar arrays and allows design flexibility.

The key point in any solar wiring architecture is to always match polarity – positive to negative terminals.

Frequently Asked Questions

How do you crimp an MC4 connector?

• Strip back the cable insulation about 7mm
• Fully insert the exposed conductor into the crimp terminal
• Use an MC4 crimp tool to compress the terminal onto the wire
• Trim any excess conductor flush with the terminal
• Push the terminal firmly into the MC4 connector body until it clicks
• Snap together the two connector halves checking for proper polarity

How do you crimp PV wire?

The steps for crimping PV wire are the same as standard building wire:

• Strip back the insulation using wire strippers
• Insert the conductor fully into the crimp terminal
• Use the solar wire-sized crimper to compress the terminal
• Trim flush and insert the terminal into the connector

Be sure to use components rated for solar use.

How do you connect solar connectors?

For MC4 connectors:

• Crimp a male terminal on the positive solar panel lead
• Crimp a female terminal on the negative lead
• Push the terminals into the connector bodies until they click into place
• Plug the two connector halves together until the latch clicks

What are the best connectors for solar panels?

MC4 connectors are the top choice for most residential and commercial solar panels systems thanks to their compact design, simple snap-fit, and reliable crimped connection.

How do you manually crimp?

Manual crimping involves using a hand crimper tool to compress the metal crimp terminal onto the wire:

• Align the terminal in the proper hex crimp nest
• Squeeze the tool handles together fully to crimp
• Rotate the tool 90 degrees and crimp again for a secure connection

Which cable is used for crimping?

Standard copper building wire or PV wire can be used with insulated crimp terminals and connectors. Typical sizes are 10 AWG to 2/0 AWG.

Welding cable also works well for the thick insulation and flexible stranding.

What is MC4 crimping tool?

An MC4 crimping tool has hexagonal shaped indents matched specifically to the metal terminals used inside MC4 connectors. It ensures precise compression for solid electrical connectivity.

What are the tools required for crimping an MC4 connector?

• MC4 compatible crimper
• Stripper for 10-6 AWG wire
• Diagonal cutters
• MC4 male and female connectors
• Male and female crimp terminals
• Multimeter to validate the crimp (optional)

Which end of MC4 is positive?

The male end with exposed tabs visible on the interior is positive. The female socket end is negative. Proper polarity is critical for MC4s.

Conclusion

Crimping high quality solar panel connections takes the right tools and techniques, but is a learnable skill. Using properly sized components, taking care to fully insert and firmly crimp terminals, and testing connections along the way will ensure reliable system performance.

With a steady hand and consistent process, you can crimp waterproof, low resistance MC4 connections that will last the lifetime of the solar installation. Just remember to always double check polarity, confirm secure crimps with a pull test, and don’t hesitate to re-do any questionable connections.