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How To Connect A Solar Charge Controller (With Wiring Diagrams)

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Every solar panel system requires a solar charge controller, which are required to properly and safely charge the batteries.

But wiring a solar charge controller can be tricky if you haven’t done it before. You will also need to buy the right size wire and fuses/breakers to complete the installation.

In this blog post, we provide a step-by-step guide, with clear & intuitive diagrams, to show you how to wire a solar charge controller in a camper van conversion.

Solar charge controller showing unknown connections
How to wire a solar charge controller?

This post will also show you how (or point you in the right direction) to:

  • Calculate the right size solar charge controller
  • Identify what wire size (AWG) you’ll need
  • Ground your solar charge controller
  • Test the charge controller for functionality

Lastly, this post will show you what tools and materials you’ll need to successfully integrate a  charge controller into your solar build.

So if you’re ready, let’s get to it.

Part 1:

Wiring Charge Controller To Solar Panels

Virtually every solar charge controller will have two input ports that will have to be connected to the solar panels. One port for the positive (+) red wire and one port for the negative (-) black wire. In the below image, you can see where these solar inputs are located on this Victron MPPT controller.

Note: “PV” stands for “photovoltaic”, which is another word for solar.

Image showing the solar input ports on a Victron solar charge controller
Solar input ports on a Victron solar charge controller

In the image below, we show a sample charge controller wiring diagram that connects the controller to two solar panels.

Note: This specific diagram is for camper van conversions, so we include an “entry gland” and “rubber grommet”. If you’ll be installing a solar system for a home, you could disregard those two products.

Wiring the solar panels to charge controller with wire size recommendations
Wiring solar panels to charge controller

In order to complete this section, you will need to know the following two pieces of information:

This is critical information to know in order to keep you and your solar system safe from short circuits and other abnormal over-current events. If you don’t know how to calculate this information yourself, read our linked posts above to help you.

Copy Our Diagram: If your have a solar array that is 440W (or less) and the panels are wired in series, you can copy our wiring diagram and use 10 AWG wires to connect the panels to the charge controller and use a 40A solar disconnect switch.

Materials You Will Need

Other than the solar panels and charge controller, below is a list of materials you’ll need. This material list works for solar arrays that are 440W, or less, with panels wired in series. If your array doesn’t fall within these parameters, you can read our above linked articles to help you size your materials.

  • Description:

    Connects electrical wire to solar panel's source cables.


Connects electrical wire to solar panel's source cables.


Protects solar wire between panels and charge controller.


Heavy-duty 'marine grade' wires that resist corrosion from the outdoor elements.

* Note: This wire spool only includes red wire. You’ll need to get a spool of black wire of the same wire gauge.

Ancor-branded wires aren’t the cheapest. But we recommend them because the wires are ‘marine grade’ and resist corrosion when exposed to the harsh outdoor environment (UV, salty air, rain). Watch our video review to learn more about them.

Tools You Will Need

To complete this section, you’ll have to cut the solar wire and strip off the insulation jacket. To do this, you’ll need a multi-tool like the one we recommend below.

Frequently Used Tool
Wire Cutter, Stripper, & Crimper (10-22 AWG)

Great tool for quickly cutting, stripping, and crimping on terminals. This will be one of your most frequently used tools when building your van's electrical system.

We earn a commission if you make a purchase, at no additional cost to you.
12/02/2023 12:21 pm GMT

Part 2:

Wiring Charge Controller To Batteries

Next, the solar charge controller needs to be wired to the designated batteries that you want to charge from the solar panels. Every charge controller will have output ports that lead to the batteries.

In the image below, you can see where these output ports are located from the same Victron MPPT charge controller.

Image of solar charge controller indicating output ports to the battery
Output ports on a Victron MPPT charge controller

The below wiring diagram shows how to connect a solar charge controller to the bus bars. In reality, we do not recommend wiring the charge controller directly to the batteries. Using bus bars as an intermediary will simplify your wiring process and keep your electrical wiring neat and tidy.

In our 12V installation guide, we show you how to wire the bus bars to the batteries.
Wiring solar charge controller to bus bars & indicating wire size.
Wiring charge controller to bus bars

Note: The specific products we list in this diagram above, like the 40A circuit breaker, assumes you have a 30A-rated charge controller. If you have a different charge controller, we recommend reading our solar wire size guide and solar fusing guidelines to get the right products you’ll need.

Materials You Will Need

  • Description:

    Ultra-flexible, high-quality copper wires to connect solar charge controller to bus bars.

  • Description:

    Distributes and consolodates power to & from the batteries. Essential for keeping wiring clean.

  • Description:

    Save money with this diverse set of lug terminals that fit 2-8 AWG wires.


Ultra-flexible, high-quality copper wires to connect solar charge controller to bus bars.


Protects 8 AWG solar wire from overheating.


Distributes and consolodates power to & from the batteries. Essential for keeping wiring clean.


Save money with this diverse set of lug terminals that fit 2-8 AWG wires.

Tools You Will Need

In order to crimp lug terminals onto electrical wire, you’ll need the following tools.

  • Description:

    Strips away wire insulation jacket to expose metal conductors.

  • Description:

    Activates heat shrink over lug and wire.


Cuts thick electrical wire (up to 2/0 AWG) to the length you need.


Strips away wire insulation jacket to expose metal conductors.


Crimps lugs on to electrical wire. Better than a hammer crimper.


Activates heat shrink over lug and wire.

To learn how to use these tools to crimp your own lug terminals, check out our video below.

Part 3:

Grounding A Solar Charge Controller

Most charge controllers will come with a terminal bolt that allows you to wire the solar charge controller to an appropriate ground point. Refer to the image below to see where Victron installs their ground terminal post.

Image of Victron MPPT charge controller indicating terminal bolt for grounding device
Terminal bolt for grounding the charge controller

However, if the charge controller is integrated into a larger 12V/24V DC system that is ALREADY grounded, then you do not need to specifically ground the charge controller. Since our camper van’s electrical system is already grounded from the bus bars, we did not utilize our Victron’s ground point.

If you do need to ground the solar charge controller, refer to the below simple wiring diagram to see how this is done.

Solar charge controller conntected to ground
Grounding a solar charge controller

Part 4:

Confirm Solar Charge Controller Is Working

Once the solar charge controller is wired to the solar panels and the batteries, it’s time to see if everything is functioning properly.

If your charge controller has a display on the unit box, read the display unit to confirm that the batteries are being charged.

If you are using a Victron-branded charge controller, you can connect the controller to your smartphone via Bluetooth using the smartphone app.

We use the Victron 100/30 controller and checking our solar harvesting data is beautifully simply. In this photo, I can quickly see that 215watts (15.60A) of power are flowing into my batteries.


Solar Charge Controller Energy Harvesting Data On Smartphone
VictonConnect App

By the way, if you haven’t yet selected your charge controller, we think Victron model charge controllers are pretty neat. Read our review to learn why.

In Review...

Solar Charge Controller Wiring Summary

If you’ve made it this far and your batteries are charging, then congratulations! You’ve successfully wired your solar charge controller into your camper van’s electric system.

Being able to charge batteries directly from the sun and being energy independent is one of the greatest feelings in van life.

For more van life solar content, we encourage you to check out our DIY solar guide for camper vans.

Or, simply head back to our DIY campervan guide.

Additional Info

Test Charge Controller For Proper Voltage

Now that you have wired your solar charge controller, it’s time to check the voltage readings to ensure everything was wired correctly. We can do this with a standard multimeter tool.

Check Battery Side Voltage

Checking battery voltage from the solar charge controller
Checking battery voltage from the charge controller

Set the multimeter to read volts and insert the positive and negative leads of the multimeter into the output ports of the solar charge controller.

Depending on the type of battery you are using and the battery’s state of charge (SOC), the multimeter should read somewhere between 10.5-14.6 volts.

If you get a reading between this range, your charge controller is successfully wired to the batteries.

Check Solar Panel Side Voltage

Next, connect the multimeter’s positive and negative leads to the charge controller’s input ports.

To get an appropriate voltage reading, your solar panels will need to be in full sun. No partial shading on the panels.

Under sunlight, check to ensure your multimeter detects a voltage coming from the panels and entering the solar charge controller.

People Often Ask...


Yes. In most circumstances, a solar charge controller is required for your solar system build. These devices are essential to ensuring your batteries are properly charged and are not overcharged, which can degrade the batteries.

The best wire size for your solar charge controller depends on the size of your solar array. Read our post to identify the best wire size for your needs.

Mount the solar charge controller on a non-flammable substrate. The electric terminals should be facing downwards.


To prevent damage to the charge controller (due to off gassing), do not mount the solar charge controller directly above the batteries.

Thank You For Reading!

We’re Yuko and Eric! We both grew up in Asia ( Japan & Hong Kong ), we left our jobs and homes in 2018 and started traveling full time from Canada to Argentina in our self-converted camper van since end of May 2019. “Asobo” means “Let’s play” in Japanese. We named our site “Asobolife” because the life is always uncertain and we live only once so it’s important to always keep positive, playful mind and enjoy the moment you are in the present. We also want to use this website to share our road trip and van building experiences to inspire our readers. We hope you enjoy!

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