Can You Solder Solar Cable? (Best Solutions)

Solar cable or Photovoltaic (PV) cable is designed to connect solar panels into an array connected to the PV solar system. The cable is flexible yet moisture-resistant, Ozone, UV, and flame resistant. These cables should last for the lifetime of the solar panel installation and, as such, be made from copper wire strands covered by at least two layers of plastic covering.

The solar cable should only be joined by MC-4 connectors, and the solar cable ends must be crimped to the correct size terminal connectors using a hydraulic crimping tool and zinc-based antioxidant paste on the cable end before crimping. A heat shrink sleeve should be fused over the connection.

It has been proven that a properly crimped MC-4 connection is superior to a soldered connection. The solar cable connection must be:

  • Moisture resistant
  • Resistant to oxidation
  • Flame resistant
  • Ozone resistant
  • Ultraviolet resistant

Solar cables and connections to the solar panel array need to withstand the onslaught of nature for a minimum of thirty years, the expected lifetime of the solar panels. Let’s look at why solar cable joints should be minimized and be made to last for at least thirty years.

Man Soldering Cable In A Workshop
Man Soldering Cable In A Workshop

Why Soldering Pigtail Joints On Solar Cable Is Not Good

Planning the wiring diagram of your solar array minimizes the number of cable connections to as few as possible. You will have two connections on each solar panel, a positive and a negative lead.

Depending on whether you will connect the panels in series or parallel, each solar panel should have no more than four connections on either end of the two connecting cables.

You should avoid splicing solar cables together to extend the cable length. The best practice is to cut each cable to length with no joints and only MC-4 type connectors at the cable end.

The efficiency of Soldered Cable

The efficient transport of electrons from the solar panels to the solar charge controller requires quality copper wire of sufficient thickness to reduce resistance to a minimum. All connections between the solar panel and the charge controller are points of potential voltage loss.

  • Stranded copper wire is the most commercially viable type of wire with low resistance and the flexibility required to route the wire around tight corners.
  • Two lengths of solar cable can be spliced together with a copper crimp connection and sealed with two layers of heat-shrink sleeves, but this should be avoided if possible.

A normal pigtail joint used on indoor wire connections is unsuitable for joining solar cable ends. The joint must be mechanically crimped and sealed with antioxidant grease and then sealed to prevent oxidation or moisture ingress.

How To Solder A Connection Joint On A Length Of PV Cable

The solar power industry has developed an ideal connector to join all solar cables to the solar panels and other branching points. These connectors are known as MC-4 connectors. The connector has a male and female end connected via internal metal joints crimped and soldered to the solar cable ends.

Once connected, the MC-4 male and female ends are sealed against oxygen and moisture ingress. The MC-4 connector is made of UV and Ozone resistant plastic that will last in outdoor applications for more than thirty years.

If you are out of MC-4 connectors and need to make a solar cable connection between two cable ends, you can make use of the following as a temporary solution.

What You Need to Solder

  1. Straight copper cable connector
  2. Crimping tool
  3. Cable Stripping tool
  4. Silver solder wire
  5. Soldering iron
  6. Dielectric grease
  7. Heat shrink sleeves x 2 pieces (one short, one longer)

Steps To Solder PV Cables

  1. Strip the protective sleeve from both cable ends, allowing a sufficient length to fit halfway into the copper cable connector. Insert the exposed stranded copper solar wire halfway into one end of the cable connector and securely crimp the cable connector over the wire end.
  2. Place the heat shrink sleeves over the solar cable and, first, the long sleeve and then the short sleeve. Now repeat the crimping connection to the other end of the solar cable. Use the soldering iron and silver solder to sweat some silver solder onto the joint.
  3. Allow the joint to cool down completely, and then apply some dielectric grease to the joint and slide the short sleeve over the joint, completely covering the copper cable connector and at least half an inch on either side of the joint. Use a heat gun to shrink and seal the joint.
  4. Allow the first heat shrink sleeve to cool down before sliding the longer sleeve over the first one and heat shrinking it in place. You should use a different color heat shrink sleeve to indicate the position of the joint.
  5. This joint will be secure and may last you for some time, but it is not guaranteed to last for 30 years, as with MC-4 connectors.

Looking for poor or broken connections during the system’s life should be avoided by exclusively using MC-4 connectors to wire up the solar array.

How To Make An MC-4 Connection On A Length Of PV Cable

MC-4 connectors have become the norm for making connections on solar cables. Solar panels can be connected in parallel or in series, or two arrays can be joined together before being connected to the solar charge controller.

MC-4 connectors come in various configurations to allow for connecting solar cables inline or in branch configurations required for parallel connections. Most commercial solar panels are already fitted with MC-4 connectors on the wire terminal ends.

An MC-4 connector consists of a plastic male and female junction that fit together to present a completely sealed and weatherproof coupling. The female plastic end contains a male metal connector inside the plastic housing.

The stripped solar cable end is inserted into this male metal connector and mechanically crimped onto the metal connector. The mechanical bond is strong enough, but many installers also sweat some silver solder onto the crimped wire to eliminate any oxygen in the joint.

Dielectric Antioxidant Grease

Some dielectric antioxidant grease is then applied to the joint. The male metal connector is then assembled into the female plastic housing, forming an airtight seal around the cable end.

Male and Female Connections

The same joining process is followed on the other end of the cable using the plastic male MC-4 housing and the metal female connector. The male and female plastic connectors can now be joined, and it will make an audible click when the two ends are properly connected.

National Electric Code

MC-4 connectors are certified by Underwriters Laboratory (UL) and comply with the National Electric Code (NEC). The locking mechanism of the MC-4 connectors will ensure that the solar cable ends will not become loose.

The plastic used for the MC-4 connectors is UV stabilized and Ozone resistant and will last in outdoor installations for more than thirty years. MC-4 connectors can be sold as single connections or branch sets.

Special tools to tighten the MC-4 connectors, seal ends, and unlock the male and female joints can be bought separately.

General Solar Panel FAQ

What Problems Do Solar Panels Solve?

In environmental terms, solar panels can potentially solve a handful of problems, including;
1. Air pollution
2. Water pollution
3. Greenhouse gases
4. Reduction in fossil fuel use

For individuals, solar energy allows you to become completely self-sufficient when it comes to your electricity needs and can save you a lot of money in the long run.

What Are 3 Important Uses Of Solar Panels?

The three most important uses of solar panels are;
1. Solar electricity. This can be used to power almost any appliance in your home, including TVs, computers, and fridges.
2. Lighting. In addition to the use of low-power, LED lightbulbs, solar panels can provide an efficient, low-cost, and environmentally friendly way to provide lighting to homes. 
3. Portable solar. In our modern, always-connected lives, our phones, tablets, and computers are almost always with us, and all run on batteries. Portable PV chargers can help keep our batteries topped up no matter where we are, as long as there is some sun to charge them.

Do solar panels give you free electricity?

Once the cost of the array is paid in full, the energy it produces is free. There are ongoing maintenance costs, too, such as annual panel cleaning, etc. 

How much will my electric bill be with solar panels?

Suppose your solar array includes a solar battery backup system, and it is large enough to fully cover your energy usage per day. In that case, your monthly electric bill will be next to zero dollars, even with a grid-tied system. 

If your solar array does not include a solar battery backup system, then at night, your house or business will use grid electricity. That cost will vary but expect to pay from 1/3-2/3 of your average electric bill, and that cost will fluctuate seasonally. 

Do you save money with solar panels?

The simple answer is, Yes, you save money with solar panels. There is an initial upfront cost, but since solar panels are warrantied for 25 years, you will save money over time. You will also begin to see monthly savings in energy bills, but there are other ways that solar panels pay you back. Those include:
1. Adding value to your home or commercial building 
2. Monthly decreases in energy costs
3. The ability to add more energy appliances without increased monthly costs
4. The potential for tax credits for going solar

Can solar panels power a house 24-7?

Most definitely! Solar panels can certainly power a house 24-7, with the addition of a high-quality inverter and a suitable battery bank, of course. To power, a house under normal usage will require a massive solar array, though, and there will be a very expensive initial financial outlay.

Do I need to tell my energy supplier I have solar panels?

This depends on where you live, but in most cases, it’s not necessary to inform your energy supplier that you have solar panels. That said, you may be producing excess power with your solar system, in which case you may be able to sell that excess power back to energy companies.

In this case, you’ll naturally need to be in contact with them. 

What Are Solar Cells Known as and Why?

Solar cells are also called photovoltaic (PV) cells. They are called so because the term ‘photovoltaic’ literally means light i.e. photo and electricity i.e. voltaic.

These cells generate electricity through the photovoltaic effect. This effect basically causes the generation of free electrons from the semiconducting silicon material of the solar panel when sunlight hits its surface.

What Type of Solar Panels Are Most Efficient and Why?

There are currently three types of solar panels available in the market that are:
1. Monocrystalline
2. Polycrystalline
3. Thin-filmed

Among these, monocrystalline solar panels are known to be the most efficient among all others.

Does heat enter your home through the roof?

Absolutely. Heat enters your home through your roof, and on a hot day your attic can get up to 150 degrees Fahrenheit or more. Through conduction, heat from the sun warms your roof which then warms your attic and the rest of your home.

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