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How to Wire a Solar Charge Controller for a DIY Camper Electrical System

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How to Wire a Solar Charge Controller for a DIY Camper Electrical System

This blog post will teach you how to wire a solar charge controller in your DIY camper electrical system. A solar charge controller regulates the power coming in from the solar array and converts it to a voltage and amperage that is safe to charge a battery bank with.

Parts & Tools Necessary to Wire a Solar Charge Controller

Column AColumn BColumn C
This parts list shows all of the parts used in this tutorial. Your wire, fuse, and ferrule sizes will vary depending on the charge controller you are using for your array.
ProductQtyLink
Victron Smartsolar Charge Controller1
Victron Lynx Distributor1
10 AWG Red Wire5
10 AWG Black Wire5
6 AWG Red Wire5
6 AWG Black Wire5
6 AWG x 5/16" Wire Lug3
6 AWG x 1/4" Wire Lug1
6 AWG Ferrule2
10 AWG Ferrule2
60A MEGA Fuse1
Cable Clamps3
3/4" Truss Head Screws3
Wire Duct1
1/4" Red Heat Shrink1
1/4" Black Heat Shrink1
1/2" Red Heat Shrink2
1/2" Black Heat Shrink4
#14 x 3/4" Pan Head Screws4
Junction Stud1
These are the tools that were used in this project.
Wire Crimper | 10 AWG - 4/01
8" Diagonal Cutters1
Wire Strippers | 12 AWG - 6 AWG1
Adjustable Wire Strippers1
Impact Driver1
Multimeter1
Phillips Head Screwdriver1
Flat Head Screwdriver1
13MM Socket1
3/8" Rachet Extension1
3/8" Rachet1
Heat Gun1
Ferrule Crimper | 10 AWG - 6 AWG1

Turn off all Power in your System

Verify that you have no power flowing in your system. This means that you need to:

  • Turn off your main battery disconnect switch
  • Unhook from shore power
  • Turn off all components (like your Inverter)
  • Turn off your Solar Disconnect Switch

Using a multimeter to check for zero voltage at your positive and negative busbars and at the wires coming from the solar charge controller is a good idea at this point.

Wire the Solar Charge Controller Equipment Ground

The equipment ground screw needs a clear path back to the negative busbar in the Victron Lynx Distributor. This is important for if there is a catastrophic malfunction inside of the Lynx Distributor, there is a path back to the negative busbar so that power can flow in order to complete the circuit which would allow the fuse protecting the circuit to blow.

This is the solar charge controller equipment ground screw:

You need a wire with a 1/4″ wire lug on one side and a 5/16″ wire lug on the other side to make this connection

  • Remove the Screw and washers using a phillips head screwdriver
  • Place the 1/4″ wire lug against the heat sink
  • Replace the washers and screw.
  • Tighten to an appropriate torque.

Screw the Solar Charge Controller to the Backer Board

Since the ground screw is in an awkward place on the side of the charge controller and makes it difficult to access once there is a component to the left of the charge controller, it’s important to make that connection first. Now you can screw the charge controller to the backer board. 4x #14 x 3/4″ Pan Head Screws work great for this charge controller.

Attach the Equipment Ground Wire to the Negative Busbar

The next step is to attach the solar charge controller equipment ground wire to the negative busbar. This will go to the center stud on the negative busbar inside of the lynx Distributor.

  • Remove the nut, washer, and lock washer with a 13mm socket.
  • Place the 5/16″ wire lug onto the stud
  • Replace nut, washer, and lock washer with a 13mm socket.
  • Tighten to an appropriate torque

Wire the Solar Charge Controller Battery Negative Wire

Now I am going to wire the solar charge controller from the charge controller battery negative terminal to the negative busbar in the Victron Lynx Distributor.

To make this connection, I’ve made a wire with a 5/16″ wire lug on one side and a ferrule on the other side.

(Note: Ferrules are completely optional throughout this tutorial, but make for a very clean install. A stripped bare copper end of stranded wire is also an approved method.)

Next, I’m going to place the end with the ferrule in to the battery negative terminal of the solar charge controller and tighten the screw.

Now I’m going to connect the end with the 5/16″ wire lug to one of the studs in on the negative busbar inside of the Victron Lynx Distributor:

  • Remove the nut, washer, and lock washer with a 13mm socket.
  • Place the 5/16″ wire lug onto the stud
  • Replace nut, washer, and lock washer with a 13mm socket.
  • Tighten to an appropriate torque

Wire the Solar Charge Controller Battery Positive Wire

Now I am going to wire the solar charge controller from the charge controller battery positive terminal to the positive busbar in the Victron Lynx Distributor.

To make this connection, I’ve made a wire with a 5/16″ wire lug on one side and a ferrule on the other side.

I’m going to place the end with the ferrule into the battery positive terminal of the solar charge controller and tighten the screw.

Now I’m going to connect the end with the 5/16″ wire lug to one of the bottom ‘fuse holder’ studs and use a MEGA fuse to connect the wire lug to the positive

  • Remove the nuts, washers, and lock washers on both of these studs with a 13mm socket.
  • Place the MEGA Fuse in place
  • Place the 5/16″ wire lug onto the bottom stud
  • Replace nuts, washers, and lock washers on both fuse holder studs with a 13mm socket.
  • Tighten to an appropriate torque

How to Wire a Charge Controller to a Solar Disconnect

Connecting the charge controller to the solar disconnect is simply a matter of connecting a positive and negative wire from the solar disconnect to the charge controller and tightening the terminals screws.

To wire the solar disconnect to the charge controller, I’m going to crimp on some ferrules onto the wires that are coming from the solar disconnect.

Wire the Solar Charge Controller Solar Negative Wire

Now I’m going connect the negative wire that goes from the solar disconnect to the charge controller:

  • Insert the negative wire into the PV negative terminal on the charge controller.
  • Tighten the screw down to an appropriate torque.

Wire the Solar Charge Controller Solar Positive Wire

Now I’m going connect the positive wire that goes from the solar disconnect to the charge controller:

  • Insert the positive wire into the PV positive terminal on the charge controller.
  • Tighten the screw down to an appropriate torque.

Use Cable Clamps for Wire Management

To keep the wires nice and tidy inside of the wire duct AND to keep the wires from wiggling out of the charge controller terminals, I’m going to put some wire clamps on the wires we just installed inside of the cable duct.

Double-check your Connections for Proper Polarity

Once all of the wires are connected, it’s time to go through and verify that positive wires are connected to positive wire terminals; and negative wires are connected to negative wire terminals. Systematically tracing each wire with your finger and pointing to the positive terminals is a great way to visualize that each wire is where it should go.

Turn on Battery Power to your System

Now I am going to turn on battery power to my system and if all goes well, I should be able to take a voltage reading with my multimeter and see somewhere in the 11-14.6V range for a 12V battery bank registering at the positive and negative battery terminals on my charge controller.

Turn on Solar Power to your System

Next, I can turn on the solar disconnect switch to connect my solar array to my charge controller. If all goes as planned, my solar array voltage should read at my positive and negative PV input terminals on my solar charge controller. Since I have 2x 100W solar panels wired in series, a reading of 44V is expected. Your solar array voltage may vary depending on it’s configuration.

Verify that your Solar Array is Charging the Batteries through your Charge Controller

Lastly, I am going to pull up the VictronConnect app on my phone and see that my batteries are indeed charging my battery bank at a rate of 15.6A

Installing a Solar Charge Controller – Finishing Up

The last steps for this project is to put the covers back on the Victron Lynx Distributor, replace the wire duct cover, and sit back and admire your handiwork on your newly installed solar charge controller.

Thanks for reading and I hope you found this blog post helpful and if you did… It’d be awesome if you would share it with somebody, or a group, who you think could use it.  Hit the like button, and leave any questions you’ve got in the comments section below.  Subscribe if you want to see more DIY camper building tutorials and I… will see you in the next project.

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Znarfski

Friday 30th of April 2021

MODIFYING "PREWIRED" SOLAR. I'm so thankful I found your channel Nate! You are a blessing to someone with minimal electrical knowledge. My goal is to be able to boondock for 5-7 days with the ability to run our led lights, fridge, water pump, charge phones and possibly run the tv/dvd occasionally. I'm starting small and leaving room to grow with a 200w solar array in series to a 40A MPPT charge with the 63a 250w disconnect. I'm doing the "solar suitcase" type of portable setup so that I can park in the shade and place the panels in the sun rather than mounting them on the rig at this point. Since the trailer is "prewired" for Zamp solar I'm planning to use mp4-sae connector for the pv wire, then tapping in behind the plug running to the disconnect and back to the battery with an inline 30a (maybe 40a)fuse. The prewired set up to have a solar panel(s) with the controller on the panel. My questions: 1. Can I get by without a bus bar? 2. Can I ground the controller to the negative wire running to the battery, or run a wire to the frame? Recommendation? 3. Can I use another disconnect between the battery and controller to take the controller offline when storing so there's not a continual draw on the battery? Maybe the controller doesn't draw that much and I shouldn't worry about it? Maybe I should just leave a panel out and let the controller run it's program to maintain the battery while it's stored? 4. I'd like to install a cigarette lighter female end on the 20A load side of the charge controller to charge cell phones, or POSSIBLY run a little old 400w inverter that we used in the car to run the tv/dvd player. Should this be OK? I tried the whole solar system setup in the back yard. I connected the inverter directly to the battery and it worked with a surge protector between the inverter and electronics. Forgot to try it on the load. I realize that the drain on our current 114Amp Hour battery may prohibit the inverter usage, but it's a new warranty replacement that I will upgrade when it dies.

It appears your forte is building systems right from the ground up so you may not want to mess with my idea, but if you're willing, any advice is appreciated. I can send photos if that's helpful, but this may already be more than you'd like to address. Thanks! Znarfski:-)

Zack

Tuesday 20th of April 2021

Nate,

Why can't you just bridge a controller's negative and the controller's chassis ground together and run only one one wire to the negative buss bar from?

Thanks!

Zack

Warren

Monday 19th of April 2021

Hi Nate. Your site has given me the confidence to upgrade my trailer. Thanks!

In most diagrams I see you recommend buying some cables from BatteryCablesUSA and other cables from Amazon "Welding Battery" Cable Wire. Is there a difference that matters? I was hoping to measure all of my cables out and buy them with the ends I need already on and BatteryCablesUSA does that.

Zack

Sunday 18th of April 2021

I've noticed that several components have two grounds, a chassis ground and a negative.

It may be a dumb question but what can't they be bridged at the unit and then have only a single wire run to the negative bus and then to ground. Like in this image here:

https://photos.app.goo.gl/qdfkpBMFPnajxDW69

I get that when the components are close to each other the point is moot but mine are only somewhat close and a "local negative bridge" would be a meaningful simplification. If it were allowed of course.

Thanks!

Brian

Thursday 8th of April 2021

Thanks for the blog. What do you recommend as a backer board? I see PVC and Plywood mentioned quite a bit. Couldn't tell what you're using in these photos.