Every camper van solar system requires a solar charge controller. If you don’t know already, these controllers are 100% necessary.
But wiring a solar charge controller in a van can be tricky if you haven’t done it before.
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 DIY camper van.
We also teach you how to:
- Calculate the right solar charge controller size for you
- Figure out what gauge (AWG) wires you’ll need
- Ground your solar charge controller
- Test your charge controller for functionality
- And more…
Along the way, we’ll show you exactly what tools and materials you’ll need to successfully wire your charge controller into your solar build.
So if you’re ready, let’s get to it!
Confused where to start with DIY solar? Check out our comprehensive camper van solar system guide to start from the very beginning.
Calculate Solar Charge Controller Size
Solar charge controllers come in different sizes. But we’re not only talking about physical dimensions. The most important thing to know here is that charge controllers are rated for different amounts of volts & amps.
Some charge controllers are rated for 20amps, 30amps, 50amps, and more…
Essentially, the larger your solar array is, the larger your solar charge controller will need to be.
To accurately size your solar charge controller, you will need to know the total volts & amps that your solar array can produce. This is determined by the total watts of your solar array AND how the array is wired together (series or parallel).
If you are not sure about all this, we put together a handy charge controller sizing guide below to help you select the best charge controller size based on total wattage of your solar array.
Solar Array Size
Buy Charge Controller
Calculate Best Wire Gauge (AWG)
Before you can wire your solar charge controller, you will need to select the ideal wire size for your system. There are two sections of wires to consider when wiring your charge controller:
- Section 1: The wires entering the solar charge controller (input)
- Section 2: The wires exiting the solar charge controller (output)
Refer to the diagram below to locate these two sections. You will need to calculate the wire size for these two sections independently.
Section 1: Solar Panels To Charge Controller (Input)
The size of the wires from the solar panels to the solar charge controller are determined by:
- The total solar array size (total watts)
- How the panels are connected together (series vs. parallel).
If you already know your array’s size and connection method, you can refer to our table below to select the most ideal input wire size for you.
Solar Array Size
Where To Buy
Panels Connected In Series
Panels Connected In Parallel
Section 2: Solar Charge Controller To Batteries (Output)
The size of the wires from the solar charge controller to the batteries are determined by the amp-rating of your solar charge controller.
If you already know the amp-rating of your solar charge controller, you can refer to our table below to select the most ideal output wire size for you.
Wire Solar Charge Controller To Solar Panels
The first step is to identify the solar charge controller’s positive and negative input ports. These ports will connect to the solar panels. For the Victron Smart Solar models, the input ports are labeled as PV (+ & -).
PV = Photovoltaic (aka solar panels)
Refer to the below image.
Regardless of whether you wired your solar panels in series or parallel, you should already have a single positive line (RED) and a single negative line (BLACK). Simply insert these two lines into their respective input ports in the solar charge controller.
If you don’t know the difference between wiring solar panels in series or parallel, check out that post to learn more.
Wire Solar Charge Controller To Batteries
To wire the solar charge controller to the batteries, you first need to locate the charge controller’s output ports. These ports are very likely right next to the wire input ports.
Refer to the below image.
Insert one RED wire and one BLACK wire into the charge controller’s output ports.
Connect To A Circuit Breaker
Take the RED wire that is connected to the output port and bring it to a circuit breaker. This breaker helps to protect the charge controller and your wires from overheating and catching on fire in case of any electrical surges.
The amp-rating of the circuit breaker is dependent on the amp-rating of the solar charge controller.
Refer to the below chart to select the best circuit breaker size for your system.
Amp-Rating (of Charge Controller)
Circuit Breaker Rating
Where To Buy?
Connect To Batteries
Once the circuit breaker has been installed on the positive line, take your RED and BLACK wire and connect them to your bus bars. If you followed our 12v installation guide, the bus bars will already be connected to the batteries.
Therefore, by wiring the solar charge controller to the bus bars, they will also be connected to the batteries.
If you are using our recommended bus bars, then you will need the following ring connectors to help connect your wires to the bus bars.
Ground The Charge Controller
It is always good practice to ground your electrical components, and this includes grounding your solar charge controller.
If you are using a Victron-model solar charge controller, you can locate the ground wire binding post on the left side of the controller unit.
To ground the charge controller, take a piece of wire and crimp a ring connector to the wire end. Then attach the ring connector to the binding post. On the other wire end, crimp another ring connector and attach it to a proper ground point on your vehicle’s chassis.
Note: You can often find appropriate chassis ground points in your vehicle’s user manual.
Test Charge Controller For Proper Voltage Readings
Now that you have wired your solar charge controller, it’s time to check the voltage readings to ensure everything was connected correctly. We can do this with a standard multimeter tool.
We can use this multimeter tool to check that electricity is flowing into the solar charge controller and out of the controller to the batteries.
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.
Helpful Tools To Wire A Solar Charge Controller
From start to finish, below are the products and tools you’ll need to wire a solar charge controller in a DIY camper van.
Where To Buy
Solar Charge Controller
Ensures proper charging of battery.
Refer to table above
Protects downstream devices from electrical surges.
Refer to table above
Power collection and distribution centers.
M6 Ring Connector
Connects positive wire to circuit breaker.
M10 Ring Connector
Connects wires to bus bars.
Cuts, strips, and crimps 10-16AWG wires.
Activates heat shrink over wire ends.
Checks electrical system for functionality.
Is A Solar Charge Controller Required?
Yes. Under the vast majority of 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.
Confirm Solar Panels Are Charging Batteries Through Charge Controller
Once everything is wired together and tested, check to see that the solar panels are charging the batteries through the solar charge controller.
If your charge controller has a display on the unit box, read the display unit to confirm that the batteries are indeed being charged.
If you are using a Victron or Renogy Rover model charge controller, you can connect the controller to your smartphone via Bluetooth and a smartphone app.
We use the Victron 100/30 and checking to see the rate at which our solar array is charging our batteries is a cinch.
With Victron’s smartphone app, I can quickly see that 215watts (15.60A) of power are flowing into my batteries.
Interested In The MOST Efficient (9BB) Solar Panels?
“9BB” solar panels are becoming the next big thing in the solar panel industry. Read our 9BB solar panel post to learn why these panels are more efficient AND have a longer usable life than traditional solar panels.
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.