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.
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.
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.
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.
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.
* 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.
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.
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.
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.
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
Tools You Will Need
In order to crimp lug terminals onto electrical wire, you’ll need the following tools.
To learn how to use these tools to crimp your own lug terminals, check out our video below.
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.
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.
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.
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.
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.
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
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...
Is A Solar Charge Controller Required?
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.
What Is The Best Wire Size For Solar Charge Controllers?
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.
How To Mount A Solar Charge Controller?
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.