In this post, we will teach how to select the correct wire size for your camper van solar array.
Going too thin of a wire and you may have a potential fire hazard on your hands. Thin wires also lead to greater loss of voltage, which ends up providing less power to charge your batteries.
But selecting too thick of wire might provide no tangible benefits and it’s just money wasted.
By the end of this post, you’ll know exactly which wire size to go with and just as importantly…WHY.
DIY Solar Build Series
Table Of Contents
From Solar Panels To Charge Controller
Let’s just cut straight to the chase. For the vast majority of camper van builds, 10AWG (American Wire Gauge) size wires will be absolutely perfect for your connections between your solar panels and your solar charge controller.
This is the wire size that we use.
Skip the fancy wire gauge calculators and the wire size vs. amperage rating tables.
We’re telling you right now, 10AWG wires are the way to go.
10AWG Stranded Wire (Marine Grade)
Why is 10AWG the most ideal wire size for solar
To answer this question, we’re going to look at three points as it pertains to camper vans builds.
1. Your Solar Array Likely Won't Exceed 30amps
Long story short, your solar array very likely won’t exceed 30amps if your array is:
- Connected in series, or
- Only consists of two strings of solar panels connected in parallel
Not sure what this means? Check out our post: Series vs Parallel Connections For Solar Arrays
This is because the current ratings for commonly sized panels to be installed on camper vans don’t come close to outputting 30amps of current.
Renogy Eclipse 100-Watt Solar Panel
Newpowa 200-Watt Solar Panel
Newpowa’s 200-watt panel is about as large as a single panel comes when purchased online. And even if you wired two of these panels in parallel, you still wouldn’t reach the 30amp threashhold.
- Operating Current: 11.76amps
- Short Circuit Current: 12.45amps
This means that if you wire your solar array smartly, you would never exceed the 30amp max rating of a 10AWG wire.
2. Current Ratings Of Solar Components
When you look at the various components that you’ll need to build your solar array (other than the solar panels themselves), you’ll realize that their current ratings very likely won’t exceed 30amps either.
These components include:
- Solar Panel Output Wires: These output wires are typically between 14-10AWG in thickness, depending on the size of the solar panel.
- MC4 Connectors: These connectors have a max current rating of 30amps.
- MC4 Branch Connectors: If you’re wiring in parallel, these branch connectors also max out at 30amps.
In essence, it is assumed that any small scale solar array, which is what you would be building on your camper van, won’t exceed 30amps.
This makes 10AWG wires a perfect choice.
3. Voltage Drop Calculations
One of the biggest arguments for going with a thicker wire is to account for voltage drop. The longer a wire run becomes, the greater the voltage drop.
The less volts, the less power charging your batteries.
However, voltage drop only becomes an issue once wire runs get longer than 30 feet. And when it comes to smaller solar arrays, like in a camper van, you’d have to have some seriously complex wiring to use 30 feet of wire.
In our van, we only use ~18 feet to wire our solar panels to our batteries.
So in reality, voltage drop is largely a non-issue for camper van solar array builds.
What About Using A Thinner Wire For Your Solar Array?
Perhaps you’re looking to save a few dollars, or you have lots of leftover thinner wire after completing other sections of your camper van electric system.
If that’s the case, you might be wondering if you can use thinner wire, like 14AWG or 12AWG, to build your solar array.
And we would say ‘go for it!’. But ONLY if you are relatively well versed in electrical safety and have done the math and calculated that your thinner wires could handle the current (AND short circuit current) of your solar array.
Interested in solar array safety? Check our post: Fuse Guidelines For Solar Arrays
Otherwise, we think 10AWG wires are the perfect (and safest) size for your solar array.
This is because:
- Solar components are rated with 10AWG wires in mind
- Minimal voltage drop will be experienced with these wires
- Sleep safely knowing 10AWG wires will safely handle the current, even during short circuit situations (assuming you wired your array correctly).
From Solar Charge Controller To Batteries
The best wire size between the solar charge controller and the batteries is trickier to calculate and depends entirely on the size of your solar array.
But simply put, if your solar array is between:
Why Wire Size Depends On Solar Array Size
Within its set parameters, a solar charge controller can accept any amount of volts or current.
However, batteries can only be safely charged within a small voltage range. Therefore, it’s the job of a charge controller to accept the total watts from the solar array (volts x current) and adjust the volts to an amount that can be safely accepted by the batteries.
More often than not, this means reducing the volts. And when volts are reduced, the current (amps) must increase in order to keep watts the same. This is because:
Watts = Volts x Amps
And so a thicker wire gauge will be required for larger solar arrays that are able to output a greater amount of watts.
Final Solar Array Wire Size Diagram
And so there you have it!
Ideally, from your solar panels to the charge controller, keep all wires at 10 AWG in size.
From the charge controller to your batteries, the size of the wire will depend on the total wattage of your solar array.
Is “Marine Grade” Solar Array Wire Worth It?
In general, we’re not super picky about the quality of our electrical wires.
Wire is wire.
We’re also building a modest camper van electrical system, not some high-tech skyscraper.
But because parts of these wires will be exposed to the elements on the roof, we think upgrading to “marine-grade” wires is a smart choice.
What Does "Marine Grade" Mean?
The standard of “marine-grade” refers to the wire’s ability to hold up against natural elements such as harsh rain, wind, and saltwater corrosion.
Therefore, if a marine-grade wire is good enough to survive a rough storm out on the open waters, it’s good enough for the roof of your van.
10AWG Stranded Wire (Marine Grade)
Final Thoughts: Safety Considerations When Selecting Wire For Your Solar Array
The biggest consideration one should think about when selecting solar array wire is safety.
If an electric wire cannot safely handle the current fed through it (whether in normal operations or in abnormal overcurrent situations) a fire can happen, which is dangerous to both your camper van and yourself.
In order to get your solar array wiring right and safe, we encourage you to read our other two solar wiring posts:
DIY Solar Build Series
Got A Question Or Comment?
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