How-to Choose Wire Sizes DIY Camper Van Electrical System

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There are many different sizes, shapes, colors, and ratings of wires.  It’s pretty confusing.  For this blog post, I’ll teach you to size wires for a DIY Camper Electrical setup and point you in the direction of the wires I recommend. Sizing the wires for your camper solar setup can get super complicated…if you let it.  So don’t let it…

Quick note before we get started.  This is just one part of an overarching “How to Install a DIY Camper Van Electrical System” series.  If you’ve just stumbled on this article directly without seeing that, there are likely some things we’ve already covered.  If you want to check out that step by step guide, you can do that here: https://www.explorist.life/diy-campervan-solar

Also, we have interactive solar wiring diagrams that are a complete, A to Z solution for teaching you exactly what parts go where, what size wires to use, fuse size recommendations, wire lug sizes, and all kind of other stuff to help save you time and frustration.  You can check that out here: https://www.explorist.life/solarwiringdiagrams/

How to Size Wires for your Solar Setup

  • Step 1: Read the instruction manual for the item you are attempting to wire.  Seriously… most of the time it tells you exactly what size of wire and fuse to use.  Trust it.  They’ve got electrical engineers backing those numbers.
  • Step 2: Use my wiring diagrams.  I have read those numbers found from step 1 and applied them to my wiring diagrams.
  • Step 3: Figure it out yourself. Which is what we are going to talk about now.

The following chart may look familiar if you’ve already been trying to find an answer to the question”How do I size my camper van wires”.  This chart, though, is a little different.

I didn’t like most of the diagrams already out there, so I made my own.  Here’s what you do.

  • Determine how many amps will be flowing to your appliance.  Find that number in the column on the left.
  • Determine how far your appliance will be from your power source.  Find that number on the top row.
    • (not round trip… this graph accounts for that)
  • Follow the column down and the row over to the appropriate box.
  • The two numbers are the wire gauges that will work for that run of wire.
    • Green = 3% voltage drop
    • Red = 10% voltage drop.
  • Try to stay closer to the ‘green’.  Red is still fine, but only for “Less important” things such as fans, lights, usb outlets, etc.
  • Consider ‘green’ as the Ideal wire gauge.
  • Consider ‘red’ as acceptable, but really try to go for green…

DIY Camper Electrical System Cheat Sheet:

Please verify using the above guidelines, but these wires will work for most situations.

Pro Tip: Be flexible in your wire sizes, if you need 3 feet of 2ga, 4ft of 4ga, and 4 ft of 6 ga; consider using 2ga for all of it and just buy a longer section of 2 ga rather than buffet style wires.

Now that you know what size of wire to use in your DIY camper van electrical system, it’s time to learn what type and size of fuses you’ll need to make sure your system doesn’t catch on fire in case of malfunction.  Check out how to size fuses here: https://www.explorist.life/what-size-fuses-to-use-for-a-diy-camper-electrical-setup/

Everything that you are learning here is put to use in our FREE Interactive Solar Wiring Diagrams.  If you haven’t yet, check them out as they are a complete solution for a camper van electrical system.  Check them out here: https://www.explorist.life/solarwiringdiagrams/

Remember, this is just one part of a full camper van electrical educational series.  To see all of the individual guides, click here: https://www.explorist.life/diy-campervan-solar

Finally, If you found this guide helpful, It’d truly mean the world to us if you’d share it with somebody who can use it, pin it to pinterest for later reference, or share it to a facebook group when somebody has a question about this subject.  Click the bubble in the lower right corner to subscribe to be notified of future updates and as always, leave any questions you’ve got in the comments below.

13 thoughts on “How-to Choose Wire Sizes DIY Camper Van Electrical System”

  1. Nate,

    First off, your tutorials are really easy to understand so kudos to you for such a great job. My question is, what determines the wire size from one battery to the next? Is it the max current that will be drawn from the batteries at any given time? I was also wondering what type of wire you recommend. I’ve seen marine grade as well as welding wire, with welding wire being a lot more flexible. Lastly, how long do you cut the wires pieces between one Battleborn and the next, assuming they are sitting side by side.

    1. What determines the wire size from one battery to the next? Is it the max current that will be drawn from the batteries at any given time?

      Yes. The battery to battery wire is sized based on the max current your system will draw. This is typically sized the same as the wire to your inverter.

      I was also wondering what type of wire you recommend. I’ve seen marine grade as well as welding wire, with welding wire being a lot more flexible.

      Of course! Here you go: https://www.explorist.life/product-category/solar/solar-wires/

      Lastly, how long do you cut the wires pieces between one Battleborn and the next, assuming they are sitting side by side.

      Rather than me telling you a measurement, it’s probably a better idea for you to mock up your own system as you start cutting the wires as necessary so you can decide if you want end-to-end or side-by-side.

  2. Ronald. Soelimto

    Hi Nate,

    Thank you for putting this very comprehensive information together.

    My wife and I are converting a skoolie and we are doing electrical now.

    My question is:
    1. The wires from the solar panel (between solar panels) to the charge controlled are 10ga and the wires between batteries and the batteries to the bus bar are mostly 2/0. You also explained that the wire size depends on the current and the distance. I wanted to make sure I got this right. The wire between the solar panels (and between the solar panels and charge controller) are smaller in diameter than the wires between the batteries and the batteries?
    2. I have 2-175 watts solar panels and 2 -100 amp batteries. I assume that majority of the wiring gauge and fuses are similar to what you have in the wiring diagram?

    Thank you

    1. Hey Ronald! Sounds like a cool project! I’ll answer your questions in line:

      1. The wires from the solar panel (between solar panels) to the charge controlled are 10ga and the wires between batteries and the batteries to the bus bar are mostly 2/0. You also explained that the wire size depends on the current and the distance. I wanted to make sure I got this right. The wire between the solar panels (and between the solar panels and charge controller) are smaller in diameter than the wires between the batteries and the batteries?

      Correct! The electrical demand (in amps) will be greater on the wires from the batteries to the busbar (largely because of the inverter) than the wires from the solar panels to the charge controller which is why the battery wires are larger.

      2. I have 2-175 watts solar panels and 2 -100 amp batteries. I assume that majority of the wiring gauge and fuses are similar to what you have in the wiring diagram?

      Mostly, yes. The main one I’d look at that may need to be changed is the wire (and fuse) between the charge controller and the busbar, but I’ll let you practice your math on that one. 🙂

  3. Hi Nate, I’m putting together a solar set up for my 5th wheel trailer. I’m using 4-300 watt Renogy mono panels a 100 watt Renogy charge controller, a 3000 watt Power techon inverter and for now 6 group 29 wet batteries with 210 RC a piece. I.m going to run the whole trailer off the inverter to the shore power hook up (we might us one of the ACs). I’m using 8awg wire from the panels to the charge controller, 1/0 cable from controller to batteries and batteries to inverter. What fuses, breakers and disconnects do I need and where. I know I have to shut off the breaker to the converter. I don’t know how many watts I would pull if everything was running. I hope this is enough info for you to help me. Thanks.

    1. Hey Rick! Sounds like a cool project you’ve got going on. I’m very close to releasing more wiring diagrams and one that would include a setup to the size that you are attempting. I know this doesn’t help you right now, but I’m hoping to have them out within the month.

  4. Hi Nate,

    If I’m running all my 12v appliances through a fuse block connected to a Yeti 1000, will I need a big chunky wire between the yeti and fuse block? Will the amps be the combined total of all the 12v appliances if I have everything switched on at the same time? (Eg 40A or so in my case).

    Thank you!

  5. I am starting a Campervan build but not ready for solar yet but want to add it later. Question? Will a solar charge controller replace my battery isolator or will I keep the isolator and add a charge controller in addition to my isolator?
    And do you have any plans for a simple setup to get started

  6. Hi Nate, Thanks for your great tutorials and information.
    I have a question; why are the wire size calculator results much different then the tables on this page?
    Am i doing something wrong?

    1. Without knowing what parameters you are inputting; it’s hard to say why. That being said, I’ve found that the charts/graphs are less accurate as they are having to generalize and make a lot of assumptions rather than having outputs based on math.

  7. Hi Nate,

    Great you are doing this and I hope you can help me out.

    I bought a motorhome so i can use it for work I’ve been told 150w 12v panel will be enough to power my fridge 24/7, lights and TV?
    What gauge wiring should I use to connect my solar panel to the charge controller? And what gauge to connect the 2 batteries to the charge controller? And what fuses will i need? Will i also require a bus bar and maybe a voltage sensitive relay or is that going over board?

    If you could answer these that would be amazing. Thank you in advance.

    Mr T

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