This blog post will teach you what size of wire you need to wire your solar panels to your charge controller in your DIY camper electrical system. We will cover the ‘technical’ way to size wire and the ‘easy’ way to size wire.

The technical way to size solar array wire involves using the EXPLORIST.life wire sizing calculator to determine the proper size of wire based on the amps, voltage, allowable voltage drop, and length of the circuit.

The easy way involves verifying that 10 AWG wire is big enough and simply using 10 AWG Wire for the solar array wiring.

## How to Choose Solar Panel Wire Size – Video

This video will teach you what size of wire you need to wire your solar panels to your charge controller in your DIY camper electrical system and will cover all of the concepts from this blog post

## Wire Size Calculator

The EXPLORIST.life wire size calculator can always be found at https://www.explorist.life/wire-sizing-calculator/ and can be easily accessed by using the main website menu under the ‘Calculators’ heading. Since it is vital to this blog post, I will also embed it here:

## Series Wired Solar Array Wire Size

A series wired solar array gets the voltage of each panel added together while the array amperage remains the same as a single panel.

This means that in the example below, there is 5 amps at 80 volts flowing through the wire from the solar panel to the charge controller.

It is 20ft from the solar array to the charge controller, which means that the 5 amps at 80 volts is flowing through 40ft of wire. Allowing for 3% voltage drop in the wire sizing calculator, we can see that we can use 16 AWG Wire for these wires.

Try it for yourself. The inputs are:

- 5 Amps
- 80 Volts
- 40 Feet
- Wire NOT installed in an engine compartment
- Only 2 wires in the bundle
- 3% allowable voltage drop

## Parallel Wired Solar Array Wire Size

To determine the wire size necessary for a parallel wired solar array, we need two separate wire size calculations. Since the voltage and amperage flowing through the wires before the combiner is different than the voltage and amperage flowing through the wires after the combiner, we need to find the recommended wire size of each.

This means that in the example below, there are 5 amps at 20 volts flowing through the 20ft of wires from each of the solar panels, 10ft away to the MC4 Combiner. Allowing for a 1.5% voltage drop in the wire sizing calculator, we can see that we can use 14 AWG Wire for these wires.

After the Combiner, since parallel wired panels get their amperages added while their voltages stay the same, the wires would be delivering 20 amps at 20 volts through 20 feet of wire, 10 feet away to the charge controller. Allowing for a 1.5% voltage drop in the wire sizing calculator, we can see that we can use 8 AWG Wire for these wires.

Try it for yourself. Here are the inputs used:

- For Each Panel to the MC4 Combiner
- 5 Amps
- 20 Volts
- 20 Feet of Wire
- 1.5% allowable voltage drop

- From the MC4 combiner to the Charge Controller
- 20 Amps
- 20 Volts
- 20 Feet of Wire
- 1.5% allowable voltage drop

## Series-Parallel Wired Solar Array Wire Size

To determine the wire size necessary for a series-parallel wired solar array, we need two separate wire size calculations similar to a parallel wired array. Since the voltage and amperage flowing through the wires before the combiner is different than the voltage and amperage flowing through the wires after the combiner, we need to find the recommended wire size of each.

This means that in the example below, there are 5 amps at 40 volts flowing through the 20ft of wires from each of the solar panel series-strings, 10ft away to the MC4 Combiner. Allowing for a 1.5% voltage drop in the wire sizing calculator, we can see that we can use 16 AWG Wire for these wires.

After the Combiner, since parallel wired series-strings of solar panels get their amperages added while their voltages stay the same, the wires would be delivering 10 amps at 40 volts through 20 feet of wire, 10 feet away to the charge controller. Allowing for a 1.5% voltage drop in the wire sizing calculator, we can see that we can use 14 AWG Wire for these wires.

Try it for yourself. Here are the inputs used:

- For each series-string to the MC4 Combiner
- 5 Amps
- 40 Volts
- 20 Feet of Wire
- 1.5% allowable voltage drop

- From the MC4 combiner to the Charge Controller
- 10 Amps
- 20 Volts
- 20 Feet of Wire
- 1.5% allowable voltage drop

## Best Solar Array Wire Size – 10 AWG

A **properly designed camper solar array** SHOULD always be able to use 10 gauge wire for all wires between the array and the charge controller, and here is why…

Even if the calculator recommends a smaller wire, like 16 gauge… 10 gauge wire is simply more durable from a physical standpoint (think; big rope vs small rope). And since it will be installed on the roof of your camper, out in the elements, having a more durable wire is a very good thing.

This ‘larger-then-necessary’ wire size will also cut down on voltage drop, which will help deliver every drop of power from your array to your charge controller.

Now… What if the calculator recommends a wire size larger than 10 AWG?

If that were the case… I’d take a step back and look at how the array is wired. For an MPPT charge controller to REALLY do it’s job, the array voltage really should be at least 20V over the battery bank voltage. This higher voltage will also keep the array amperage lower, which will let us use a smaller wire size.

## How many watts of solar can run on 10 AWG wire?

High-quality 10 gauge wire with 105-degree celsius insulation is rated with a max ampacity of 60A. Most MC4 connectors, on the other hand, have a max ampacity of 30A; so we need to keep the array amperage below 30A; and we can do that by wiring the array in series or series-parallel so the array has a lower amperage and a higher voltage.

This means that with an array amperage of 30A, feeding say… 250V into a big SmartSolar MPPT 250|100… Using watts law of 30A x 250V… this would actually give us an array wattage of 7500W of solar panels; which is a LOT. In fact… that’s about 150% the max rated wattage capacity of that SmartSolar MPPT charge controller when paired with a 48V battery bank. So the wattage of the array…doesn’t REALLY matter when trying to see if we can use 10 gauge wire.

So, if you are trying to design a solar array on your own… use the ‘technical’ methods I taught you earlier to double check that 10AWG is indeed large enough and again… if 10 AWG isn’t large enough… consider re-working your array design to have more panels in larger series strings to boost the array voltage and lower the array amperage so you CAN use 10 AWG wire.

## Why not just use larger than 10 AWG Wire?

Generally, the only reason a solar array would need to use larger than 10 AWG wire would be to reduce the voltage drop from the array to the charge controller. Since we are talking about camper solar arrays where the length of the entire camper is likely under 45ft, though… The chances of the wires from the array to the charge controller being over, say, 50-60ft would be rare. On a properly designed solar array, achieving a 3% or less voltage drop with 10AWG wire is easily achievable.

Mark

Sunday 19th of March 2023

Hi Nate - The ubiquitous Blue Sea Systems Wire Gauge Selector Chart differs wildly from what your calculator recommends. Where your calculator recommends 16AWG, Blue Sea recommends 10AWG - under exact same conditions (5A, 40’). Please clarify?

Thank you!!!

Kay

Tuesday 7th of February 2023

Regarding post that is pending, (Kay, Feb 3 @ 4:03pm) you can delete, I've change to a smaller inverter/charger. Thanks for this website, I have learned a lot!

Kay

Friday 3rd of February 2023

Hi Nate, Short version is we followed someone else's diagram and now we are thinking it wasn’t so good after much research, our bad. We purchased your wiring diagram for 3000w inverter/charger last night, would have loved to do a consult but see that is not offered at this time. I have a few questions, one having to do with the solar panels first.

1. We have two 200W solar panels 9.66 amps, 27 Voc (if I am looking at correct numbers) wired in parallel 10 awg coming from the panels to the Branch Y Connectors. I watched the video and read the accompanying blog about how in parallel there may be too many amps after the connectors to use the 10 awg. I did try your interactive calculator but it wasn't working (I know you said you got rid of a lot of the interactive) any way I went on a few sites and think I see that either 8 awg or 6 awg would work Can you confirm this for me, this is about a 10 ft run. I also saw where you said to wire in series and that could be a consideration maybe but I’m trying to make work what is already there.

2. Our wiring of our batteries in parallel then to the 3000W inverter/charger we had wired using 2/0. After much research now we see that 4/0 seems to be the correct size wire. Just would like to confirm this with you. I have found many different answers to this question.

3. At the moment we have a ground from the Inverter/Charger, busbar and Mppt to a ground point on the van using 6 awg, (another suggestion (from a electrician this time) we are thinking too small now?

This is what we have to work with. Many of these items have been purchased over the last two years and are all being implemented now so I would like to try and stay with what we have as returns on many may not be an option and many are already mounted as well.

2015 Ford Transit 150 Medium roof Victron Energy MultiPlus 3000VA 12 V Pure Sine Wave Inverter and 120 amp Battery Charger Victron Energy Smart Solar Mppt 100V 30 amps Victron Energy BMV-17 Smart Battery Monitor SOK 206ah 12v LiFep04 battery (two of these) Victron Orion-tr Smart 12/12 volt 18 amp 220W DC to Dc Charger Isolated (bluetooth)

We have run wires for the smaller things such as switches and lights, Max air fan etc I am comparing what we have already done to what your diagram says and will make appropriate changes but the above questions are beyond my capabilities (this all is!)

Robert

Monday 2nd of January 2023

Where do the 15 amp MC4 fuses go in the 1200 watt solar panel array in the 50 amp retro fit diagram? Should they be 25 amps because 300W ÷ 12Vdc = 25 amps. Neither the purchased 50 amp retro diagram nor the website's 1200W array diagram has them shown. Please help !!

Nate Yarbrough

Sunday 15th of January 2023

This video shows that: https://youtu.be/b2H8vpj8rQg

Scott

Monday 2nd of January 2023

Maybe a little off topic, but we purchased an Ecoflow Delta Pro to assist with A/C power in our 5th wheel. Not long term, but enough to run an A/C for the animals for short periods while we shop or stop to eat. One thing I didn’t consider is the converter in the trailer taking power (abt 500 watts) from the Delta Pro to charge the batteries (2-100 ah BB lithium). We can turn off the breaker off on the converter, to eliminate the draw from the Delta Pro.

Additionally, we would like to install solar on the roof and use the pre-wired (10 ga) solar prep. The Delta Pro will accept a max of 15A, 11-150 V and 1600 W from solar. Looking at starting at 400 watts (2/200-watt panels) on the roof and we have enough room on the roof to get close to 1600 W maximum if we decide to upgrade in the future.

Is there a way to provide power via solar to both the Delta Pro and the onboard batteries?