How to Build and Crimp Solar Extension Cables with MC4 Connectors

Absolutely loved the tutorial. Thanks

Ok so I did connect it correctly. I am doing a backup with 2 solar panels 400 watts 10 gage. next is batteries and inverter. not easy to do.

Actually it has been discovered for a few years now that the flow of current goes to the negative side..

This is the best video by far I have seen on crimping and connecting MC4 connectors. Appreciate the closeups and detailed explanations.

This video would have been 100% perfect if u had shown us how it was connected from the panels. We the newbies 😢

Did u plug the positive to the negative or did u plug positive to positive to extend before plugging in the batteries

MC4 is a brand. There arw similar designs. However, you must use same brand +ve or -ve. Please cal, them positive and negative as moulded on the aide. NOT male or female.

This video is very handy I need to put ends connectors on a couple of solar panels i have. I had to break the end connectors off to get the solar panels off from the tree connectors.

I generally solder the wire interface after crimping it. It turns out to be really easy to flow solder into it. Be sure not the get solder onto the little metal tabs that seat the pin in the housing. The MC4 will last pretty much forever if you do that. It is not officially required to solder, but its a good idea. MC4 crimps are not cold welds.

Another differentiator is the current rating for the MC4 connectors themselves. There are both 20A and 30A rated MC4s. Always buy the 30A rated connectors, they are generally higher quality. I see a spattering of "50A" rated MC4's advertised but I wouldn't trust them for 50A.


Be sure to use the correct crimper. Basic crimpers don't curl the metal into the wire. MC4-specific crimpers have a double-rounded edge to curl the metal properly.

Do not twist the stranded copper wire. If you do, then the crimp will break copper strands as it forces the metal tabs into the wire.

Use tin-plated copper cable or straight copper cable, stranded in both cases. But do NOT use "poofy" cable (cable with too many copper strands). If you use stranded copper wire that is not tinned, always solder to protect the interface from oxidation. I solder after crimping either way.

Do not use solid copper wire. It must be stranded, and not have too many strands.

Use 10AWG or 6mm^2 "solar" cable. 6mm^2 cable is slightly fatter than 10AWG. Even if you aren't pushing a lot of current you want the losses to be as low as possible. Best to use the properly-rated cable for the application.

Generally speaking, do NOT use MC4 splitters or combiners. Those pieces of plastic with one MC4 on one end and two or three or more MC4's on the other end. These tend to be very low quality and may overheat.

To be honest, it is always a good idea to use a proper combiner box with proper per-string fusing, even if you only have two strings. Not only do you have to ensure that the cables and panels for any individual string remains safe in the event of a short causing all the other string(s) to push their full current into the shorted string, but also the combiner box has other great features too like a master breaker (useful when doing maintenance) and surge protection devices.

I stopped using MC4 connectors over one year ago. In my view the lack of manufacturing tolerances makes them dangerous, particularly in high amperage setting. The MC4 connectors will Overbay loverheat and melt..

Usually 6mm² or 4mm² cable is used. This is AWG 10 or 12
But it must be solar cable that is weather and UV resistant.
The cable should have the print: „H1Z2Z2-K“
„PV1-F“ Cable was previously used and is usually not UV resistant.

What is the largest wire that Mc4 will except.

My system is 8AWG by design. I now have the opportunity to move my panels closer to the inverters and want to shorten the 8AWG solar wire (just like yours, just 8AWG). I have the correct MC4 connectors designed specifically for 8AWG. They do not have the two legs to crimp. They are just a cylinder just like yours have but without that area you crimped. The circular tube the wire slides into is the only thing to crimp. What type of crimper should I use? Is a "barrel crimper" what I need?

Helpful video thank you

In any system or circuit, DC or AC, if voltage goes up, amperage goes down (and vice/versa). Always. Voltage & Amperage are inversely proportional. Your total power (P) is Watts. Watts= Volts (E) x Amps (I), the total number in Watts (P) or in VA (volt/amps) will always remain the same so if one of the two (volts/amps) goes up or down, the other must do the opposite.

Just done this myself. It's easy. If I can do it, anyone can. I now have my second solar panel up and charging my new Bluetti. Yay! No need for crimpers, pliers do the job easily.

I am new to this DIY Solar. Any ideas on where to find a crimper for 8 gauge wire? I intend on using this size of wire for my installation.

Nice kit.

Try it, and still no power through the cord.

You're supposed to put the terminal into the crimpers and squeeze just enough that it hold the terminal, then put the wire in, instead of putting the wire into the terminal and then trying to hold it together when you put it in the crimper. That's why it ratchets down instead of just opening back up freely.

as far as the disconnect tool goes, it doesn't work, I use some needle nose pliers. I mean for disconnecting the wires.

I actually enjoy making cables. I made a lot of my own, including a few exras.