How to Build Solar Extension Cables with MC4 Connectors

How to Build Solar Extension Cables with MC4 Connectors

In this post I will explain how to make DIY Solar Extension Cables with these MC4 connectors. MC4 connectors are by far the most common connectors used on solar panels. I will show how to select the correct solar wire and how to install these MC4 connectors. I have several of these cables around that I use with my Bluetti AC200 Max and my 24v DIY Solar Generator

If you learn to put MC4 connectors on solar extension cables, you will not only be able to have cables that are the exact length you need but you will also be able to tackle just about any situation that comes up regarding solar cables. At times I’ve needed to cut the MC4 connectors off of a cable in order to fish them through a small opening. Then I had to re-install new MC4 connectors. After reading this post, watching the video and with a little practice, you will be able to build solar extension cables like a pro. If you just want to know how install the MC4 connectors, you can use the chapters to jump straight to that part of the video.

If you have not seen MC4 connectors before, let me show you just a little about them.

Here is the anatomy of MC4 connectors. All these pieces work together to make sure the connection is water tight. The male MC4 connector is on the left and the female is on the right. These can be confusing when you first work with them because the male connector actually has the female terminal on the inside and the female connector has the male terminal on the inside.

To connect them, you simply push these together. I noticed that some of these make a click when they are connected and others don’t. I would just give them a tug to make sure they are connected correctly. These connectors are water proof with an IP67 waterproof rating which just means you can leave them out in the weather. They are also UV resistant, but preferably you should keep the connectors out of direct sunlight if possible. To disconnect them, you can use your fingers to squeeze here while pulling the connectors apart. This can take a little practice. If you find you can’t do this, I have a link at the bottom of this post for a kit that has a tool that helps take these apart. You just put the tool on like this and then they will come apart. I have done this a lot and I don’t use the tool anymore.

If you are making your own complete extension cable as I am doing in this post, the first thing you need to do is to select the correct wire. Don’t use just any wire. You need to make sure the wire says it is solar or PV wire in the description. That is important because solar wire has a thicker, tougher insulation that is made to stand up against the harsh UV rays of the sun and freezing temperatures. Solar wire is also rated for direct burial. I suggest that you choose high quality solid copper stranded wire for best results. This wire is tin coated copper wire.

You will need both red positive and black negative wire. You can typically buy these together as set. I’ll put a link below to everything I am using for this demonstration.

After ensuring you are looking at the right wire, you now need to determine the size of wire you need. In most situations I’ve seen, 10 gauge wire was being used and that will most likely work in the majority of the cases. However, you need to select the gauge wire that fits your needs. If you choose a wire size too small, you could be creating a fire hazard. The size wire you choose is based on the current (or amps) going through the wire. The amount of current going through your wire depends on the solar panel (or panel array) you are using. Most situations are different. I have a chart I will show that can be used as a general guide to help choose the right size wire.

Here are a couple of examples:

  • If you have just a single panel rated at 11 amps, this chart says you should use 12 gauge wire.
  • If you have two of these same panels wired in series, then the voltage doubles, but the amps stay the same at 11 amps. So again you would still use the 12 gauge wire.

But, If you have two of these same panels wired in parallel, then the amperage would be doubled to 22 amps. According to this chart, you should use 10 gauge wire. So you just have to calculate how many amps will be travelling through the solar wire and choose the correct size for your situation. Having said all of that, I would suggest you always choose 10 gauge or larger wire. You may later add a panel or change your solar panel array or make some kind of upgrade, you may find yourself in a situation where your solar wire is now too small. And if you forgot to consider your solar wire in the upgrade, you may have just created a possible fire hazard. As I mentioned earlier, in most cases 10 gauge solar wire will be sufficient. So if you determine you need 12 or 14 gauge wire, then I suggest you just go with 10 gauge instead. But if you calculate you need 8 gauge wire, then you should definitely go with 8 gauge wire. However, if you find you need 8 or 6 gauge solar wire, you may want to consider reconfiguring your solar panels so they produce 30A or less because the 6 and 8 gauge connectors and other tools for those are harder to find.

Be careful to pay close attention to the wire you may need in different places on the way to your solar charge controller. If you have wire going into a combiner box, you have to make sure the wire coming out of the combiner box is sized appropriately. That may be different coming from the panel into the combiner box.

You also need to consider the length of the wire. When you have long spans of wire there is something called voltage drop. This just means that when you have a long extension cable, you will have less voltage at the end of the wire than you started with. The thicker the wire, the less voltage drop you will have. I would say if you have less than maybe 20 – 30 feet of wire, I would not worry much about it. But if you have longer than 20 or 30 feet of solar wire, then you should to take this into consideration. Its just a matter of how much voltage drop is acceptable to you. Voltage drop is a subject that could be a whole video in itself. So I’m not going to go into all those details for this video. I’ll put a link in the description to a good video that covers voltage drop in depth. There are also online calculators out there that will help you with this. When I installed my mobile solar array, I had to run about 70 feet of solar wire over to it. I ended up going with 8 gauge wire. The MC4 connectors you buy typically state the wire size in AWG that can be used with them. Most that I have seen only support up to 10 gauge wire. So be careful when purchasing those.

The last thing I wanted to mention about wire size is that the majority of MC4 connectors are only rated up to 30 amps. I believe I have seen higher amperage MC4 connectors, but they will be harder to locate. So be sure you can find the right MC4 connectors for your wire size before finalizing your purchase.

Now that you have selected your wire, you will need to purchase the MC4 connectors. You can get these on Amazon and other places. There are also these tools you will need to make the connections. So to make it easy, I ended up buying this BougeRV kit which has all the tools you need as well as 6 sets of connectors. Each MC4 set is for one wire. Female on one end and positive on the other. So if you make both positive and negative wires and you need connectors on both ends, you will use 4 of these out of the 6. You can buy more separately as I have done here.

Before creating the solar extension cables, make sure the positive and negative wires are of the same length. Another thing to point out is that on each wire you will put a male MC4 connector on one end and a female on the other. Like this wire.

The positive wire coming off of a solar panel should always be the male connector.

The male should plug into the female in the direction of the flowing current.

Now let me show you how to make these wires.

I will be using 10 gauge solar wire. This cable will just be used for general purpose use. And these MC4 connectors from the BougeRV kit supports 10-26 gauge wire and up to 30 amps.

I highly encourage you to watch the YouTube video (link at the top) which will be much easier to understand since you can see everything.

So the first step is to strip the wire about half an inch. Be careful not to cut the wire strands.

Since we are first connecting the male connector, you need to slide the female terminal over the wire and crimp it using this crimping tool from the BougeRV kit. Choose the correct slot in the crimping tool for the correct wire size you have. I am using 10 gauge wire, so I will choose this slot here. Be careful to make sure the connector is positioned like this so that the crimp will be good. This curve should be positioned like this so that the terminal curves over onto the wire when crimped. If you position is incorrectly, you may not get a good crimp. Now squeeze as far as it will go and release. Look at the crimp and make sure the terminal folded both sides over and into the cable.

After the crimp, slide these two pieces over the wire like this and then slide the male body over and push down until you hear a click. Don’t forget to slide these pieces over first, or you will have wasted this terminal. Simply twist the base until tight. You can use these tools to ensure a tight fit. These tools go on like this and you turn until it slips loose. It almost acts like a torque wrench.

Now the male connector is on. Give it a good tug to make sure it is connected good.

Now to connect the female connector, it is the same process, but using the female connector.

Now the positive wire is done.

You should follow the exact same process for the negative wire.

After you complete that, you are almost done.

You can just leave the solar extension cables loose like they are. Or I actually like to take electrical tape and wrap around the two wires about ever 6 feet or so to keep them from flopping all over.

Well, I hope you enjoyed this video of building your own solar extension cables with MC4 connectors. If you did enjoy it, please like the video. It will help my channel out a lot. Also consider subscribing you you don’t want to miss any of my upcoming videos

Thanks for watching!!

Affiliate Links:

BougeRV Solar Crimper Kit – https://amzn.to/3OAcldK

Solar Wire 10AWG/30 feet – https://amzn.to/44Cxxp7

Extra MC4 Connectors – https://amzn.to/3KkOtIG

BougeRV 200 watt Solar Panels – https://amzn.to/40itNa4

Bluetti AC200 Max – https://amzn.to/42IV0UW

Bluetti 350 watt Solar Panel – https://amzn.to/3ZjNLA6

PV Solar Extension Cable – https://amzn.to/3LYVAbh

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I cover a variety of preparedness and self sufficiency topics such as DIY Solar Generators, Living Off Grid, Generators, Vegetable Gardening and growing your own food, Water and Food Storage, Water Catchment, Emergency Lighting, Product Reviews and other topics I’m interested in.

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