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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.


Ryan Meldrum

Thursday 16th of March 2023

Nate,

First of all thanks so much for being an amazing resource. I am in the process of planning the systems for a 1946 Spartan Manor TT. I am trying to determine the wire sizes needed due to the extended distances. Finding some conflicting numbers I hope you can clarify.

12v, 60amps, 18ft one way. (This is from the battery to 1 of 2 dc fuse boxes)

Your chart for sizing says 0AWG. The calculator say 4AWG (18ft) and 2AWG (36ft). This all for DC with 3% drop.

Can you please clarify? Can’t wait to purchase as much as I can from your family.

Thanks, Ryan

Dave Masopust

Thursday 22nd of December 2022

Hey Nate,

The information you provide has been very helpful, as well as inspiring!

My question about wire sizing is a bit different. We have a pick-up truck camper to which we would like to add a Victron Orion 30amp DC to DC charger. We currently have a 200ah Lithium battery, but plan to add more battery power in the future, and may add another charger then. Our truck has a 397amp alternator, which I would like to take advantage of!

The distance from the starter batteries on the truck to the house battery compartment in the camper is roughly 30 feet, so I've been factoring that as 60 feet of wire. Could I run 2/0awg from the starter battery on the truck to buss bars in the battery compartment in the camper - then I'd connect the chargers to the buss bars with 6awg pigtails?

The dealer where I bought the camper offered to do the install, but told me he'd run 6awg for a single charger. That didn't sound like enough wire to me.

I'd appreciate any feedback and help.

Thanks!

Mike

Sunday 11th of September 2022

Hi,

Question about calculating the length of a wire run when thinking about voltage drop.

If, for example, I am trying to calculate voltage drop for my battery-> inverter run and:

-inverter to bus bars is: 5ft red 5ft black -bus bars to batteries: 5ft red 5ft black

Am I doing 2 separate voltage drop calculations for this? Or 1 calculation with a total length of 20ft?

Do you have to add the length of cables connecting your batteries together to these lengths or are all those separate calculations?

Hopefully my question is clear, thanks!

Chris Rondestvedt

Thursday 8th of September 2022

Hi Nate,

During 2020 I was part of your crew when you helped me install a Solar system in my RV (2019 Coachmen Prism 2300DS wired for 30Amp shore and generator power; 6x170W ZAMP Solar Panels; 5x Battle Born 100 Ah LiFePO4 Batteries; Victron Multiplus 12/2000 120V; Solar Control MPPT 150/85; Color Control GX with VeBus connection and WiFi installed; Generator Cummins Onan 3.6_3.6KYFA-26120). This allowed 2 years of self contained camping allowing support of my wife's 110V CPAP.

I'm now looking to upfit to the Multiplus 12/3000 120 V only. After reading the manual closely it appears I only need to

1. Replace battery terminal 2/0 cables with 4/0 cables (4/0 is 107.2 mm2 vs two1/0 = 2x53.5 mm2=107 mm2). Appendix A locations G and H 2. Install AC 50A fuse in sub panel fed by inverter via 6/2 wire to accommodate Power Assist (30A shore power + 25 Amp Power Assist = 55 Amp) My WF-8930/50 sub panel is rated at 50 Amps 3. Replace 300A ANL battery fuse with 400A ANL fuse

But what is unclear in the manual Appendix A is that wiring locations for battery + and - (connections G and H ) have M8 battery terminals while the "PRIMARY GROUND" connection F is noted as M6. The manual requires the wire upgrade from the battery/bus to multiplus II be 4/0 but

1. What gauge wire is used for the Primary Ground location F with its smaller terminal? (Note on my current 12/2000 you recommended this wire be the same as the 2/0 to the battery bank/bus bars) 2. What is its purpose of this ground, AC or DC? and 3. Where does its other end connect to?

In addition

4. My current system uses 2/0 wire between the battery posts. Do I need to change these to 4/0 as well?

Best,

Chris

David

Tuesday 28th of December 2021

Using a induction cooktop and nespresso machine at the same time in combination with other 12v appliances, I expect I might use up to 500 amps at peak usage, what wire size would I need for this system between the batteries? Does the 4/0 AWG from the wiring diagram work for this?

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