I cannot stress how important this part of the installation is. I have seen many people purchase the best solar panels and charge controller only to connect them with cheap, undersized wiring that they have leftover in their homes. Using the proper sized wire and the proper type of wire is vitally important to ensure that you get the most efficiency out of your solar panels and charger.  Additionally, chosing the wrong wiring could create a fire hazard. Here is what to look for:

  1. Use the proper sized wire to assure that resistance is kept to a minimum.  Less resistance in the wiring means increased energy efficiency. Undersized wiring will lead to increased resistance and loss of energy to heat (wires will get warm). In extreme situations you can even risk fire or wire damage if you do not plan properly. If you don’t know what size wiring to use, then consult with an electrician or with the place in which you purchased your solar panels and charge controller. If there is a question, err on the side of caution and use larger sized wire.
  2. Since some of the wiring will be mounted on the top of your RV and exposed to sunshine all the time, make sure it is UV resistant. It will last much longer and make for a much better install.  Additionally, protect the wiring exposed to the sun by covering it with split loom.
  3. Use stranded wire and not solid wire. Stranded wire is much more pliable and bendable and will be less likely to fail or break while installing it and fishing it through small spaces in your RV. Similarly, it is those same properties that will allow it to last longer since an RV shakes and rattles while traveling, which could lead to solid wire eventually cracking or breaking.

In my case, I chose to use 8 Gauge, 150V, low energy underground or low voltage cable that is UV resistant for my connections between panels and from the panels to the solar charger. Remember, the longer your wire run the more resistance. The length of the wire run plays a large part in determining the size of the wire needed. Therefore, make sure to use the shortest wire runs possible from point A to point B, without leaving excess wire bunched up in a corner.

Following is a basic chart that can help you to figure out what sized wire you will need.  The distances below are one way from point A to point B.  Remember, larger gauge wire has a smaller number associated with it.  For example, #4 gauge wire is thicker than #10.

  Wire Gauge
Amps #14 #12 #10 #8 #6 #4 #2
1 84 feet 131 feet 206 feet 337 feet 532 feet    
2 42 feet 66 feet 103 feet 168 feet 266 feet 432 feet 675 feet
4 18 feet 33 feet 52 feet 84 feet 133 feet 216 feet 337 feet
6 14 feet 22 feet 33 feet 56 feet 89 feet 141 feet 225 feet
8 10 feet 16 feet 27 feet 42 feet 66 feet 108 feet 168 feet
10 8.5 feet 13 feet 22 feet 33 feet 53 feet 84 feet 135 feet
15 6 feet 8.5 feet 13 feet 22 feet 35 feet 56 feet 90 feet
20 Do not use 6.6 feet 10 feet 16 feet 27 feet 42 feet 67 feet
25 Do not use Do not use 8 feet 13 feet 22 feet 33 feet 54 feet
30 Do not use Do not use 6.6 feet 11 feet 18 feet 28 feet 45 feet
40 Do not use Do not use Do not use 8 feet 13 feet 21 feet 33 feet

In addition to using the correct sized wire, make sure that you make quality connections. If you are attaching terminals to the end of your wires, use a proper crimping tool. Soldering the wire to the connector after crimping can also help to make the install last longer. If you decide to solder your connectors in addition to crimping, be sure to use rosin core solder and not the acid core solder used in plumbing.

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