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How To Easily Design And Install RV Solar – Part 2: Installation

PublishedJune 10, 2019

We covered the general thought process behind Camp Addict co-founder Kelly Beasley's RV solar system installation in Part 1.

There, we planned a 600 watt RV solar system installation.

Now we will learn about the actual installation of an RV solar system.

Rooftop solar install done side view

It's good to have a plan laid out so that you have an idea of what you want to accomplish with the solar install.

Still, you should be prepared to have some things not quite work out as you had planned.

When I was doing the final planning of Kelly's solar installation (including ordering equipment and supplies), she was camping elsewhere.

 So I was relying on my memory when it came to things like how far it was from one area of her rig to another.

We had done the initial rooftop measurements long before we pulled the trigger on the installation.

Therefore, as far as figuring out the nuts and bolts of things, I was on my own without having her trailer right in front of me.

This means I wasn't quite accurate on some things, including how much wiring to order.

As good as I thought my plan was, it wasn't good enough.

We ended up ordering additional supplies and making several unplanned trips to the hardware store. 

  • This is part two of Kelly's RV solar installation where I talk about the actual installation of solar components, including equipment installed, and tools used. Part one covered general RV solar system planning and is where to go if you want to understand why I chose what size wiring, solar panel wattage, solar controller size, etc, etc, etc.

Rooftop Solar Prep And Installation

We purchased three solar panels (200 watts each) for a total of 600 watts of solar.

This included two rectangular panels and a single square panel.

These panel shapes were selected based on the usable roof space we had mapped out in the initial planning stage.

We had room for two rectangular panels in the left rear corner of her rig, and space for a square panel in the right front corner.

Products Purchased

Solar Panel

Solar Panels - We purchased three 200-Watt solar panels directly from Continuous Resources.

Two rectangular panels and a single square panel.

Removing The TV Antenna

There was a batwing TV antenna that was taking up a lot of space in the right rear corner of her rig.

We originally planned to work around this (as well as all the other 'components' already installed on the roof).

However, once we got up on her roof to start the installation, Kelly decided the TV antenna was more of a nuisance than anything.

TV antenna removal

Removing The TV Antenna

She never watched terrestrial TV, the antenna rattled in the wind, and it took up a huge amount of roof real estate.

So the first order of business was to remove the antenna and cover up the hole with a sheet of aluminum sealed with Dicor.

This freed up a great deal of roof space and allowed us to reconfigure the solar panel layout.

TV antenna assembly off

Removing The Antenna Assembly

TV antenna hole covered

Antenna Hole Covered

Finalizing Solar Panel Layout

We ended up putting the two rectangular panels along the right side of the RV, and the square panel in the left rear corner.

This spacing kept the panels as far away from the air conditioner unit as possible, minimizing shading.

Another advantage of the final solar panel placement is that there is plenty of room to walk between the panels when she gets on the roof.

Roof ready for solar panels

Finalizing Layout

Solar Panel Bracket Installation

Once we figured out where the solar panels went, it was time to install the solar panel brackets.

Kelly's roof is, well, it's interesting. It isn't the most solid RV roof in existence.

The manufacturer cut corners here and didn't use any solid plywood subroof under the top 'layer'. 

Instead, there is just a top layer of a fiberglass flimsy board laid on top of trusses.

Solar panel brackets installed and sealed

Brackets Installed & Sealed

This made for an interesting time walking around (making sure to walk on the trusses, otherwise the roof flexed considerably).

Technically Kelly's RV doesn't have a walk-on roof.

At least I wouldn't consider it to be one. 

Thank you 'high quality' RV manufacturer.

The lack of any subroof means that we had to be very careful where we installed the solar panel brackets.

We wanted to have the brackets screw into trusses.

Otherwise, they wouldn't be 'biting' into much.

Solar panel bracket mounting holes drilled

Pilot Holes Drilled For Bracket

Of course, the spacing of the roof trusses did not match the length of the solar panels, so we couldn't have both the front and rear brackets both be screwing into trusses.

We opted to have the front brackets 'bite' into something, leaving the rear brackets to screw into just the roof material.

Solar panel bracket being screwing down

Screwing In A Bracket

Solar panel bracket installation

Bracket Installed

To locate the solar panel brackets, we installed them on the solar panels themselves and brought everything up on the roof.

Using a stud finder, we located the trusses and positioned the solar panels where we wanted them.

We outlined the 'feet' of the solar panel brackets so we'd know what area we needed to clean up prior to the final installation. 

We drilled pilot holes using the existing holes in the bracket feet.

The brackets that we used came pre-installed with 3M VHB tape on the bottom of them.

This was perfect since Kelly's roof is, in theory, a fiberglass roof.

Solar panel bracket location cleaning

Cleaning Bracket Location

Once all pilot holes were drilled, it was time to clean the roof surface so that the VHB tape would adhere to the roof.

We cleaned up the roof using a Scotch Brite™ pad and did a final cleaning using rubbing alcohol.

After removing the brackets from the solar panels, we peeled off the VHB tape backing, carefully placed the brackets over the pre-drilled pilot holes, and screwed the brackets to the roof.

Solar panel bracket sealed

Solar Panel Bracket Sealed

Self-leveling Dicor lap sealant was used to seal around each bracket (where it 'met' the roof) and over each of the screws.

This ensures that no water will be able to enter the roof through the screw holes.

Once the Dicor had been given plenty of time to set up, we attached the solar panels to the brackets, finalizing the actual solar panel installation.

We left cardboard covering the solar panels until we were ready to activate the system so that the panels wouldn't produce any electricity.

Products Purchased

Solar Panel Brackets

Solar Panel Brackets - We purchased three sets of solar panel mounting brackets directly from Continuous Resources (the same place we purchased the panels from).

They offer both a tilting and non-tilting option. We opted for non-tilting (flat mount) brackets.


Dicor Self-Leveling Lap Sealant

Dicor - To seal the screws and the base of the mounting brackets, we used Dicor self-leveling lap sealant.

You can purchase this by the tube. Use the self-leveling version on horizontal surfaces.

A non-sag version (not self-leveling) is available for vertical surfaces, but not something normally used on the roof.

Solar Panel Roof Wiring

The solar panels each came pre-wired with a length of 10 AWG wire with MC4 connectors on the end.

However, we had to add wire to extend each solar panels wiring to reach the combiner box (which we located inside).

Solar panels installed

Solar Panel Wiring Coming Together

We chose to use an MC4 'Y' branch connector to combine the leads from the two rectangular solar panels into one set of leads (four wires into two).

This reduced the number of wires running across the roof and down through the refrigerator roof vent.

A 15-amp fuse (in a waterproof, MC4 in-line connector) was used for the two rectangular panels and with the square panel (total of 2 fuse holders).

You would use a fuse appropriate to the size panel(s) you are protecting.

MC4 branch connector and inline fuse

MC4 Branch Connector & In-Line Fuse

This also meant that we only had to run four extension wires, and only install four MC4 connectors (one to each end of the four extension wires).

We installed ring terminals on the other ends of the extension wires (more on this in the combiner box section below) once we determined how long each wire had to be to run thru the roof vent, to the combiner box.

MC4 connector and inline fuse

MC4 Connectors & In-Line Fuse Holder

Once we had the rooftop wires running where we wanted them, including down through the roof vent to the combiner box, we Dicor'd the wires to the roof.

We temporarily held the wires in place using electrical tape while the Dicor set.

Wires entering roof vent

Solar Panel Wires Entering Refrigerator Roof Vent

We put a couple of layers of Dicor over the wires, letting the Dicor dry between applications.

This 'over puddling' meant that the wires were firmly held in place by the Dicor.

Note: We installed the ring terminals (for attaching to the combiner box) before we connected the solar panel wire extensions to the MC4 connectors from the existing solar panel wiring, and before we added the Dicor to hold the wires in place.

We will discuss the ring terminal installation in the combiner box section below.

Products Purchased

Windy Nation solar panel wire with MC4

Solar Panel Wiring 10 AWG - To extend the wiring from each solar panel to the combiner box, we had to purchase additional 10 AWG solar panel wiring (UV and weather resistant).

There are several different brands of quality solar panel wiring you can get. We link to Temco 10 AWG solar panel wiring below. Choose your length and color.

Pro tip: You can buy one color for both negative and positive runs, which means purchasing a single spool. This allows you to not end up with short lengths you can't use. Simply put the red heat shrink on black wire to signify positive leads (or vice versa if you only purchase red wire).

Choose Color & Length

MC4 Connectors - We purchased MC4 connectors to connect the solar panel wiring to the solar panels. Buy as many as you need - one pair per solar panel.

You can buy them in sets of 6 or 12 pair.


Windy Nation MC4 branch connector

MC4 'Y' Branch Connector (pair)- We purchased a single pair of MC4 'Y' branch connector so that we could combine the wires from the two rectangular solar panels together.

This resulted in only four wires needing to go through the roof vent to the combiner box.


MC4 in-line fuse holder

MC4 In-Line Fuse Holder- You should fuse each panel (or pairs of panels if you wire yours as we did on the two rectangular panels). 

This in-line fuse holder has MC4 connectors, is waterproof, and just 'snaps' in place. 

You can purchase the same holder with different sized fuses, depending on your needs.

Choose Fuse Size


MC4 Crimper Tool

MC4 Crimper Tool - You need an MC4 crimper tool to install the MC4 connectors to the one end of the solar panel wiring that you purchased (above).

Getting Power To The Solar Controller

Once the solar panels were mounted on the roof, we had to run wiring to the solar controller.

This consisted of 'combining' the solar panel wires into a single, larger pair of wires.

We ran them straight down to the belly of the rig and forward to the solar controller compartment.

Combiner Box Installation

I chose to install the combiner 'box' inside Kelly's rig for a couple of reasons as explained in part I of the solar installation.

There just happened to be a perfect location inside the rig, right next to the refrigerator roof vent 'inlet'.

This eliminated the need for a waterproof box on the roof.

Marshall installing combiner box

Marshall Working On Combiner

Because the combiner was installed inside and didn't need a waterproof enclosure, I didn't use a box.

Instead, I used two power distribution blocks - one to combine the positive wires and the other to combine the negative wires.

I used 4-post blocks, which allowed me to attach three 'inputs' (two from the solar panels and a third from ground deploy wiring) and one output (to the solar charge controller).

Ring terminals installed

Ring Terminals On Wires From Solar Panel

The studs of the distribution blocks are 3/8 inch in diameter.

Because the walls of the pantry are thin board, I installed the power blocks on a small piece of plywood, which I then attached to the pantry walls.

A hole was drilled in the side of the pantry to gain access to the refrigerator vent area and run the wires coming in from the roof (and the ground deploy) to the power distribution block (combiner box).

Combiner box installed covers off

Combiner Installation (covers off)

Combiner box installed covers on

Combiner Installation (covers on)

6 AWG welding cable was then installed (see next section) as the 'output' of the combiner box to run to the solar controller at the front of the rig.

Ground Deploy Solar Panel Wiring

During Kelly's solar system installation, we opted to wire in the ability to connect an optional ground deploy solar panel.

Why?

In case her rooftop panels are shaded by trees and she needs the ability to have solar panels away from her rig, in the sun.

We purchased a length of 10 AWG wire that came pre-installed with MC4 connectors on one end.

Ground Deploy MC4 connectors

Ground Deploy MC4 Connectors At Lower Fridge Vent

This was 'snaked' through the lower refrigerator vent, up behind the fridge, and joined the rest of the solar panel wiring at the combiner box.

This allows any ground deploy panels to be controlled by the main solar controller.

All that is visible is the pair of MC4 connectors poking out from her lower fridge vent.

5 months after the install, Kelly has yet to plug in any ground deploy solar panels, despite boondocking 100% of the time.

But the ability is there, just in case.

Products Purchased

4-Post Distribution Block

4-Post Power Distribution Block (pair) - Because the combiner 'box' went inside, it didn't need to be an actual weatherproof box.

So we went with a pair of these power distribution blocks. Easy peasy!

We purchased two pairs of these as another pair was used during the solar controller installation.


10-12 AWG 3:8 ring terminals

3/8" 10-12 AWG Ring Terminals - These ring terminals went on the ends of the 10 AWG wire running from the solar panels to connect them to the distribution blocks.


Heat Shrink Assortment

Adhesive Heat Shrink Kit (130 pieces) - Heat shrink is used throughout the solar install.

Use heat shrink with an adhesive liner, for better corrosion resistance. 

This kit gives you lots of choices as far as diameter, so you can use it for the install and future electrical projects.

Wiring From Combiner To Solar Controller

I ran 6 AWG welding cable from the combiner to the solar controller.

This wire size was chosen based on the calculations I made during the planning phase of the solar system installation.

The end of the welding cable that attached to the combiner (power distribution blocks in the case of Kelly's install) had wire lugs attached to them.

Once attached, the wire lugs were put on the distribution blocks so that one end of this wire run was secured.

Because we were dealing with many feet of welding cable, I ended up feeding one end up through the belly and up the pantry, to where the combiner box was mounted.

This allowed for the long end of the wire to be under the belly (resting on the ground) while I figured out where to attach it as it was routed forward.

Attaching Wire Lugs

During this solar installation we dealt with a couple different sized wiring - 10 AWG and 6 AWG.

For the wiring ends (ring terminals) that we attached to the 10 AWG wiring (specifically the terminals used to attach the 10 AWG to the combiner), we used a hand crimper.

10 AWG isn't that large and small enough to crimp a terminal by hand.

For the 6 AWG terminals (wire lugs) we used a hammer crimper (see below 'products purchased' feature).

The wire lugs used for this sized wire are pretty beefy and not something you can crimp by hand.

Wiring lug placed in hammer crimper

Wire & Lug In Hammer Crimper

Wiring lug hammer crimper in action

Striking Crimper With Hammer

When attaching wire lugs you want to make a VERY secure connection between the wire strands and the lug/terminal itself.

If you do a half-assed job, then electricity won't flow freely.

This will cause major problems from an electrical standpoint (as in your system will not function properly or to its full potential).

This is not a place to cut corners!

You will also want to add an anti-oxidant compound to this connection. Put some of the compound on the bare wire ends and work it in (a little, don't go crazy and mess up the strands) with your fingers.

Wire lug stamped

Crimped Lug

Wiring lug completed

Completed Lug With Heat Shrink

Also, put a little into the part of the lugs that the wire fits into.

This compound helps keep corrosion at bay.

We also used heat shrink with an adhesive liner at each of these connectors.

The heat shrink protects the wire to lug connection from shorts as well as provides additional corrosion protection.

The adhesive inside the heat shrink 'oozes' out as the heat shrink tightens down, and creates an impenetrable seal.

I was able to run the wire straight down the pantry (drilling small holes to facilitate this) and through the floor.

The power distribution panel is below the pantry, which means that there were existing holes in the floor where wiring was already passing thru.

I simply removed the existing caulking (seal) and fed the positive and negative cables through an existing hole.

This meant I didn't have to drill a new access hole at this point. (I resealed this hole once wiring was completed.)

Underbelly wiring secured

Wiring Secured With Zip Ties

The belly of Kelly's trailer isn't covered, so all existing wiring and the trailer frame are exposed.

This made it relatively simple to run the welding cable forward to where it needed to go back up through the floor to connect to the solar controller.

If your RV's belly is covered, this step will be a bit more difficult.

I wanted to protect the welding cable as much as possible as I ran it forward.

So I had it lie next to existing wiring, which was against the frame (a pretty protected location).

Zip ties were used to secure the welding cable at fairly short intervals.

Wiring installed under belly

Wiring Running To Solar Controller

Cable clamp installed

Cable Clamp Installation

The solar controller (see below) was going to be installed in the center of the forward luggage compartment.

This meant I had to get the wires to the middle of the trailer.

Which was away from the frame.

The frame is what I was using as an attachment point.

For this section of wire, I used cable clamps that I screwed directly into the belly of the rig (that has an aluminum sheet as the bottom part of the belly).

I had to drill a round access hole in the floor right beneath where the solar controller was going to be installed so I could run the necessary wiring up through the floor.

Drilling hole in floor

Drilling Hole Thru Floor

Products Purchased

Windy Nation 6 AWG welding cable

Windy Nation 6 AWG Welding Cable (black/red) - This is high quality, pure copper cable that provides a good 'path' to get the power from the distribution blocks to the solar controller.

We used the same wire to run from the solar controller to the batteries. Buy enough (more than you think you need) after measuring the wiring runs.

Choose Length


6 AWG 3:8 wire lug

3/8" 6 AWG Wire Lugs - These wire lugs went on the ends of the 6 AWG welding cable running from the distribution blocks to the solar controller.

And from the solar controller to the batteries (via the battery monitor shunt).

We used a hammer crimper tool (see below) to make a very secure, mechanical connection between the lugs and the wire.


Klein Tools cable cutter

Klein Tools Cable Cutter - When cutting welding cable to the appropriate length, you want a high-quality cutter. 

Welding cable is a bit thick, so your basic side cutting pliers aren't up for the task.

These cable cutters make short work of thick welding cable.


TEMCo Hammer Lug Crimper Tool

TEMCo Hammer Lug Crimper Tool - For larger wire lugs you need to have some sort of heavy-duty crimping tool.

We used a hammer crimper (you use a hammer to pound on the crimping head) for the larger diameter wire lug ends. 

This creates a very secure mechanical connection between the wire lug and the wire strands.


Ox-Gard Anti-Oxidant Compound

Ox-Gard Anti-Oxidant Compound - When putting wiring connectors on the end of cables, you really should use an anti-oxidant compound to help prevent corrosion.

You work this into the bare wire ends with your fingers, as well as putting a little inside the wiring connector end (where the wire goes) before assembly.


Zip Ties

Zip Ties - Zip ties were used to secure the welding cable to the frame as it was run forward, under the trailer, to the solar controller location.

Zip ties are also used to secure the wiring running from the solar controller to the batteries.

And they are generally very handy to have for other projects on your RV.

Choose Length

Solar Controller Installation

You want to mount the solar controller as close to the batteries as possible, while still protecting it from the elements.

Kelly's trailer batteries are mounted on the tongue, out in the open, so this wasn't a good location for the solar controller.

Solar controller wall being installed

Installing Solar Controller Mounting 'Wall'

I chose to mount the controller inside the forward pass-thru baggage compartment, which meant a fairly short wire run from the controller to the batteries.

The back wall of the compartment was chosen as it was vertical and allowed for a secure mounting point.

Because the wall of the baggage compartment is made from the same thin board that the rest of the walls in the RV are made from, I had to provide a way to mount the solar controller firmly (so it wouldn't break off the wall).

Solar controller wall completed

Completed Solar Controller Mounting 'Wall'

This was done in two stages:

  1. I mounted a piece of plywood on the wall that was wide enough to span two of the aluminum wall frame supports. The plywood was screwed directly into the aluminum, making a very solid mounting base.
  2. I mounted the solar controller, circuit breakers, and power distribution blocks to a second, smaller piece of plywood. This allowed me to do a bit of pre-wiring of components before putting this assembly inside the cramped baggage compartment.

Products Purchased

Victron SmartSolar MPPT 100:30 solar controller

Victon SmartSolar Solar Charge Controller  - We opted to go with a Victron solar controller and specifically their line of Smart Controllers (which simply means Bluetooth capability is built-in).

They offer a BlueSolar line that is similar except without the built-in Bluetooth (you can purchase an optional dongle).

We went with the 30/100 controller for Kelly's setup.

Choose Capacity


Surface Mount Circuit Breaker

Surface-Mount Circuit Breakers - We used surface mount circuit breakers so that we could electrically isolate the solar controller.

This required two breakers for Kelly's solar system. A 30-amp breaker between the solar controller and the solar array.

And a 40-amp breaker between the solar controller and the batteries.

Choose Amp Rating

Solar Controller Sub-Assembly

It wasn't just the solar charge controller that was being mounted inside the baggage compartment.

We also needed to install a way to electrically isolate the controller (via circuit breakers) and a way to distribute the solar controller output (via distribution blocks).

Rather than trying to mess with all these components while working in the confines of a baggage compartment, I had the brilliant idea to create a sub-assembly that consisted of all these components.

That way I could easily install one part that consisted of multiple parts.

Victron SmartSolar MPPT 100:30 solar controller

Victron SmartSolar MPPT Solar Charge Controller

I found a piece of plywood that was large enough to mount the controller, two circuit breakers, and a pair of power distribution blocks (positive and negative) and laid out the components, allowing for room to run 6 AWG wire.

Once I settled on a location for the components I screwed them to this piece of plywood.

One circuit breaker is used between the positive wire coming from the combiner box and the PV (solar array) input of the solar controller.

This allows you to disconnect the solar array from the solar controller.

Solar controller sub assembly being built

Putting Together Solar Controller Sub-Assembly

The other circuit breaker is installed between the positive output of the solar controller and the power distribution block that feeds both the battery and the RV's power distribution panel.

This allows you to disconnect the solar controller from the batteries.

The combination of these two circuit breakers allows you to totally isolate the solar charge controller from the rest of the RV's electrical system.

Solar controller sub assembly completed

Completed Solar Controller Sub-Assembly

The power distribution blocks (one for positive, and one for negative) are used to tie together the batteries with the RV's power distribution center and the solar controller.

Therefore the solar controller can 'feed' both the RV's 12-volt system for power use during the day, as well as provide power to recharge the batteries.

I made short wire assemblies (6 AWG) to connect one circuit breaker to the solar controller's positive input (PV input).

The positive output of the solar controller was wired to the other circuit breaker (then onto the positive power distribution block).

The negative output was wired to the negative power distribution block.

Solar controller sub assembly installed

Solar Controller Sub-Assembly Mounted In RV

This was all the wiring I could do to the sub-assembly before final mounting inside the rig.

But it did save a lot of hassle by not having to work in a cramped space, and the result was some very nicely laid out components that were easily installed inside the baggage compartment.

Solar Controller Final Installation

Once the solar controller sub-assembly was completed (as much as possible outside the rig), I crawled inside the baggage compartment and attached it to the plywood wall I had previously installed.

All that was left was to hook up the welding cable that was coming from the solar panels (via the combiner box), as well as hook up the power to the RV's power distribution panel and batteries (see below).

Solar controller completed installation

Solar Controller Wiring Completed

Now that the solar controller was in its final position, I knew how long the cables from the combiner box had to be.

These were cut and wire lugs were installed.

Solar controller distribution blocks closeup

Distribution Blocks (covers off) Close-Up

Solar controller breakers closeup

Circuit Breakers Close-Up

The positive wire from the combiner box went to the circuit breaker that fed the solar controller,.

The negative wire went directly into the solar controller (both on the PV input side of the controller).

We left the circuit breakers in the 'open' position until we were ready to activate the system so that no power would unintentionally 'flow'.

RV Power Distribution Center Wires

The original way Kelly's trailer was wired had the power distribution center (the thingy with all the fuses and what supplies all the 12-volt systems in the rig) being wired directly to the batteries.

Once the solar controller was installed, things had to change.

I re-routed the positive and negative wires that supply the power distribution center from the batteries up through the hole I made in the belly of the RV.

Wiring running thru hole in floor

Wires Running Thru Floor To Solar Controller

These wires were now terminating at the power distribution blocks that are part of the solar controller sub-assembly.

This meant I had to cut the wires and install new lugs so they could attach to the distribution blocks.

Sealing Up The Hole

Once I was done running wires to/from the solar controller in the baggage compartment and had secured the wires to the belly of the rig so they wouldn't flop about, it was time to seal up the hole I had made in the floor.

There are many ways you could do this.

I chose to use some duct putty that I had lying around to do the initial seal job.

This also kept the wires away from the metal edges of the hole.

I simply stuffed a bunch of putty up into the hole and between the wires.

Wires thru floor sealed

Sealant For Wires Running To Controller

Then I topped things off with a good amount of silicone sealant, so make sure no bugs, moisture, dirt, etc could find its way up into the hole.

Getting Power To The Batteries

The final wiring run went from the solar controller to the batteries.

This normally would be a fairly easy task, except we had a battery monitor in the mix.

This meant careful consideration of where to place the battery monitor shunt and the associated wiring.

More on this in the battery monitor section below.

The existing wiring at the front of the trailer was a mess!

Ugh, it was sooooo poorly done. 

This is not surprising as many RV manufacturers do what's easiest for the production line.

This doesn't bode well for longevity.

Tongue wiring before

Tongue Wiring Before

Tongue wiring after

Tongue Wiring After

I tore out the existing rats nest of a wiring mess in the tongue area, and redid it all.

Cleaned it up and wired it so there should be no problems in the future (unlike the past).

We used 6 AWG wire between the solar charger and the batteries (mounted on the trailer tongue).

Overall this was a fairly short run of 4-5 feet.

Marshall installing wiring under rig

Marshall Working On Wiring Under RV

The positive cable ran directly from the distribution block at the solar controller to the batteries (via the catastrophic fuse).

The negative cable made a trip to a ground bar I installed on the backside of the trailer frame, to the battery monitor shunt, and finally to the negative terminal of the batteries.

Ground block installed

Ground Block

Ground block installed

Ground Block

Because RVs are chassis grounded, the negative lead of the battery is connected to the trailer frame.

And then the negative (ground) wire of all 12-volt systems are in turn connected to the trailer frame.

The frame is used as the path for the negative (ground) side of the 12-volt electrical system.

Ground block wired

Ground Block With Wiring

The way Kelly's trailer was originally wired had the main battery chassis ground out in the open on the trailer tongue. I relocated it to a new ground bar I installed on the backside of the frame. I chose this location for a couple of reasons:

  1. It's fairly well protected from the elements, being on the backside of the frame and close to the floor of the rig.
  2. Because of the way battery monitors work, the shunt has to be between any load and the negative terminal of the battery (otherwise it won't 'see' the load). This means that the negative lead of the battery had to go to chassis ground after the shunt (or between the shunt and the solar controller). The location of the ground bar allowed for this.

Products Purchased

Murray Ground Bar Kit

Ground Bar  - We had to relocate where the battery went to chassis ground. The best way for us to do this on Kelly's RV was via a ground bar.

Catastrophic Fuse

We chose to install a catastrophic fuse directly at the positive post of the battery.

Can't get any closer to the battery than this!

It was a simple installation - terminal fuse mounted on fuse block, fuse block attached to battery positive terminal, and positive battery lead attached to fuse block.

Done.

Catastrophic fuse installed
Catastrophic fuse installed

Products Purchased

Blue Sea Systems Fuse Block Terminal

Terminal Mount Fuse Block - This Blue Sea Systems terminal mount fuse block accepts many different sizes (amperage ratings) of fuses and mounts directly to the positive terminal of your battery.


Blue Seas Systems Fuse Terminal

Terminal Fuse - This square fuse fits the above fuse block.

We used a 50-amp fuse as the catastrophic fuse for Kelly's rig (keeping in mind that we didn't install an inverter so maximum load isn't that much). 

You should choose the amp rating based on your RV's needs.

Choose Amp Rating

Battery Monitor Installation

The final piece of the solar installation was the battery monitor.

I think that this is a crucial piece of equipment for any serious solar installation.

I don't believe it's optional.

I explain why in part I of the solar installation.

Battery Monitor Components

The battery monitor consists of two main components:

  • The shunt
  • The display

The shunt is what monitors the flow of power in and out of the batteries.

Any battery load MUST take place after the shunt (on the side of the shunt away from the battery) in order for it to read the load.

Victron Shunt

Battery Monitor Shunt

Victrom BMV-712 Battery Monitor display

Victron BMV-712 Battery Monitor Display

If there is a load coming off the batteries between the shunt and the battery ground post, then the shunt cannot 'see' it.

Therefore it doesn't know this load is using battery power.

Since we were adding the battery monitor into Kelly's electrical system, we had to relocate where the battery chassis ground connected so it would be after the shunt.

Mounting The Shunt

The battery monitor shunt has to be very close to the batteries so that there are no loads between it and the negative battery terminal.

Yet the shunt needs to be protected from the weather.

I've had a Victron battery monitor installed on my trailer for several years now.

I made the mistake of mounting it between the battery boxes on the trailer tongue, exposed to the elements.

Even though I mounted it inside what is supposed to be a weatherproof box, water still manages to get inside.

I've replaced the shunt twice despite it being mounted in a 'watertight' box (and have taken steps to make sure I don't need to a third time), so I'm very aware of the need to mount the shunt in a location where it won't get wet.

Battery monitor shunt in junction box

Battery Monitor Shunt In Junction Box

Ideally, you would mount the shunt inside.

With Kelly's rig, where her batteries are located, this just wasn't practical.

So I did the next best thing.

We went down to Home Depot and purchased a plastic weatherproof junction box, which was installed upside down against the floor of the trailer.

I screwed the shunt to the box.

I then drilled a hole on either end of the box to let the negative wire (6 AWG) enter/exit the box to connect to the shunt.

The shunt and monitor communicate via a cable that looks very much like a telephone wire, so this too has to enter the junction box.

Juction box sealed

Junction Box Sealed

There also is a wire that connects between the positive terminal of the batteries and the shunt. This is how the shunt gets power (it has a circuit board) and reads battery voltage.

Once all was determined to be good, I sealed the holes with silicone sealant to ensure moisture would stay out.

Because of the location tucked up against the floor, and just aft of a frame bulkhead, the junction box receives very little moisture, so the shunt is kept dry.

Mounting The Display

The battery monitor's remote display can be mounted virtually anywhere in the RV.

Battery monitor display and bezel

Battery Monitor Display & Lock Ring

The cable that runs between the display and the shunt is quite long, so your mounting option is pretty much wide open.

Kelly opted to mount her display at her pantry because this allowed her to see the display when sitting at her booth.

It also made it easy to run the wire inside the rig.

I just used the same hole that the 6 AWG wire running between the combiner and the solar controller used.

Battery monitor install hole

Battery Monitor Display Mounting Hole

Mounting the display is pretty simple once you find a location.

You do have to have access to the back of the mounting location so you can secure the mounting lock ring and plug in the cable.

Simply use a hole saw to cut the size hole called for in the quick install guide, mount the display, and plug in the cable.

It's that simple.

Battery monitor display mounted

Battery Monitor Display Installed

Cable Between Shunt And Display

The cable that allows the battery monitor shunt to communicate with the display was run through the same route of the welding cable between the combiner box and solar controller. 

I zip-tied this cable the same way I zip tied the welding cable.

Very straight forward.

Products Purchased

Victron BMV-712 Battery Monitor with temp sensor

Victron BMV-712 Battery Monitor  - We opted for the Victron BMV-712 battery monitor which has built-in Bluetooth capability so it can 'talk' to the solar controller.

It also allows you to monitor it via the Victron app on your smartphone. 

We highly recommend that you get the optional battery temperature sensor cable (shown above).


Junction Box

Junction Box - A weatherproof, dustproof place to install the shunt if you cannot tuck it away inside. 

We purchased one from Home Depot, but this one is very similar.

Just choose what size you want. You will need to drill holes in the sides to run the battery (and other) cables into the box.

Choose Size

Activating The System

Once all components were installed and wiring was run, the very last step was to activate the system.

Power was applied to the overall electrical system by first connecting the positive lead to the battery, then the negative lead.

The RV came back to life, which was a great sign!

It meant we wired the basic 12-volt system correctly. (Whew)

Rooftop solar install done looking forward

Completed Installation (looking forward)

Now to check the solar system...

First I turned on the circuit breaker between the batteries and the solar controller so that the controller 'came to life'.

This allowed me to check/change the configuration of the controller before switching on the solar array.

I made sure that the appropriate LEDs of the solar controller blinked and that the settings were correct (both the rotary switch and the app settings) before trying out the solar panels.

I then climbed on the roof and removed the cardboard from the solar panels.

I did this during a sunny day (duh!) and while monitoring the Victron app on my iPhone.

Sure enough, the solar array made power!

Rooftop solar install done looking aft

Completed Installation (looking aft)

I verified this by looking at both the solar controller on the app (to see what it was receiving from the solar panels and what it was sending to the batteries) and the battery monitor via the app (to verify that electricity was flowing into the batteries).

I was a bit shocked that things worked the first time around.

As I mentioned previously, electricity isn't my strong suit and even with all the planning I did, I was half expecting something to go sideways.

But it didn't!

Conclusion

Kelly is now 5+ months into using her 600-watt solar array and it has been working perfectly.

It did take a bit of dialing in as far as the battery monitor settings go, but this is all done via the Victron app and is just trial and error.

You have to adjust the settings based on the batteries you have, etc, so that the monitor doesn't reset to 100% prematurely (and to ensure that it does reset when your batteries are fully charged).

Marshall in pass thru compartment
Marshall under rig

The actual install wasn't super horrible.

My back did hurt for a while afterward, but that's because I'm not young anymore and was in some pretty contorted positions crawling in, and under, the RV.

That was seriously the worst part about the install - my back.

LOL!

It did take a while, but that's to be expected considering it was my first installation.

I learned a ton and am not afraid of taking on this task with a future rig.

Marshall Headshot

Camp Addict co-founder Marshall Wendler brings his technical expertise to help explain RV products in an easy to understand fashion. Full-time RVing from April 2014 - December 2020 (now RVing about 50% of the time), Marshall loves sharing his knowledge of the RV lifestyle. Marshall spends the majority of his RVing life boondocking. He is the part of Camp Addict that knows 'all the things'. He's good at sharing his technical knowledge so you can benefit. 

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  • Just came to thank you so much for these great tutorials. I just finished installing and activating our solar system and your two posts were referred to the most often during my planning phase and install phase. I added an inverter/charger as well which you didn’t do, but all of your info was incredibly helpful.

    • Hi Liz,

      You installed your own solar system! That’s fantastic- we hope you enjoy it! It was like NIGHT and DAY for myself… after my install, I wondered why I hadn’t done the roof solar sooner. I dealt with moving around, deploying, and breaking down (and breaking) portable panels for what… three+ years?

      So glad we could help! Thank you for letting us know. We sure do appreciate you taking the time to give us this feedback! 🥰

      Enjoy your new system!

  • Hi I just found your page and have read Jack’s pages as well that you linked. I have a few questions about fuse sizes and placement.
    1) I’ve seen elsewhere recommended to have a small fuse on the power line to the battery monitor, but I don’t see that on your install. I was thinking just a simple in-line car blade style fuse would probably do the trick there? (and bonus I already have some of those on hand)
    2) I also was wondering how to size the shunt, as well as the catastrophic fuse. I am installing a small system of 400W of panels, and a single 100AH battery currently, including an inverter. Our trailer is smaller than Kelly’s so for the most part our wiring sizes are the same and the equipment is comparable.

    • Hi Liz,

      Thank you for the comment and for checking out Camp Addict!

      1) The battery monitor receives its power through the telephone line that connects the monitor to the shunt. Therefore the shunt itself is providing power to the battery monitor and there is no separate fuse between the monitor and shunt. The shunt itself gets power from the positive terminal of the battery). This power line comes with a fuse, so the shunt has a fused power source. You can see a picture of this power lead in the ‘Products Purchased’ box for the battery monitor above. (Keep in mind this is how a Victron battery monitor receives its power. Other brands may be setup differently.)

      2) The Victron battery monitor comes with a single size of shunt. It’s a 500 amp shunt for the battery monitor we show in this article. Plenty big for just about any RV installation. Your catastrophic fuse will need to be sized according to the amperage draw of the inverter. Since Kelly’s rig doesn’t have an inverter, we opted for a 50 amp catastrophic fuse. But that most likely won’t be large enough for the inverter you are installing. The inverter manual should say what the amperage draw is.

      Thanks again for the comment. Hope that helps!

  • Thank you for the detailed photos and descriptions. I’m installing solar on my TT gradually, starting with the charge controller for use with my portable solar panel, and I’m following mainly your article (but also others) and using your affiliate links. But I do wish your photo titled “Solar Controller Wiring Completed” showed the grounding wire for the charge controller installed.

    • Hi Rolf,

      You are very welcome! I’m glad you are finding this post useful during your solar install.

      Which grounding wire are you referring to? The chassis ground screw on the side of the controller? If so, we didn’t use that ground. It is our understanding (and we confirmed this with a friend who does solar installs) that this is a redundant ground path when you have a ‘normal’ chassis ground situation.

      While it wouldn’t hurt anything if you had a separate ground wire to this screw/stud, it isn’t necessary for most normal installations.

  • This is exactly what I needed thank you so much. I have 3 questions.

    1) I have an inverter/charger already installed, so would the only addition to this setup be to simply hook the inverter cables up (negative to shunt and Positve directly to battery terminal)?

    2) if I have a ground bar already attached to the frame would I just used that one as wired and run negative ground from distribution block to that then shunt?

    3) is it necessary to run the house dc through distribution block as opposed to running directly to battery. What are pros and cons?

    Thank you so much. I’ll be starting almost this exact install next weekend.

    • Hey Chris,

      Glad you found this useful!

      1) I’ve never wired an inverter, so I’m not certain how it should be wired. Lot of help I am, right? I do believe you are correct in that the inverter has to be fed directly from the battery. And the negative side does need to be on the RV side of the shunt. So it sounds like you are correct, but I’m not certain.

      2) Yeah, if you have a good ground bar already, you can most likely use it. However, if it’s anything like the ground bars on my rig, you have to insert a bare wire into it. You cannot use ring terminals. I kind of like using ring terminals, but I may just be weird that way. 🙂

      3) The advantage of using a power/distribution/whatever you want to call it bar is that you can have one lug per ring terminal. In other words, you aren’t stacking ring terminals on top of each other. If you ran the distribution panel wiring directly to the battery, then at the very least you would have that ring terminal, the ring terminal for the inverter, and the ring terminal from the solar charge controller. I believe there is some general rule about how many ring terminals you should stack on top of each other, but I don’t know what it is off the top of my head. It’s just easier if you have less ‘stacking’ at the battery, in my opinion.

      I hope that helps! Have fun with your project! I hope electricity doesn’t frustrate you as much as it does me sometimes. 🙂

  • After reading your article I have a question. How did you incorporate the existing RV charging systems into your solar panel battery array? Example, plug in rv park power and tow vehicle charging circuit. Thanks

    • Hey Mike,

      So the RV park power (120-volt power source) goes directly into your RV’s power distribution panel (the thing with all the fuses and circuit breakers). It is then converted into 12-volt power to charge the RV battery(ies) and power the 12-volt systems on the rig.

      You don’t have to do anything with this 120-volt power supply when you are installing solar as you aren’t touching this part of the RV’s electrical system.

      The 7-pin connector from the tow vehicle also is wired separately and you don’t have to worry about it either. Well, let me just say this about that. I’ve done both Kelly’s and my RV now (installing solar) and haven’t touched the 7-pin wiring.

      What you do have to be concerned about is the 12-volt power to/from the distribution panel and the battery. I touch on this subject right here in the above page.

      There is a wire from the battery(ies) to the power distribution panel. This is how the battery(ies) provide power to the RVs systems when you aren’t plugged into shore power. And also how shore power charges the batteries when you are plugged into a 120-volt power sourse.

      What I did (and as far as I know, is the way most/all RVs would have to be wired) is splice into the wiring between the distribution panel and the battery. I installed a positive and a negative power bar, which I then attached the wiring to/from the battery, wiring to/from the power distribution panel, and from the solar controller (solar power source).

      Positive wiring to one power bar and negative wiring to the other power bar.

      This ties the solar into the battery so it can charge it, while keeping the ability for the battery to power the RVs systems (via the power distribution panel), and the distribution panel keeping the ability to charge the battery(ies). And the solar is a one-way power source in that power will flow into the power bars (thus charging the battery and powering the RV’s 12-volt systems) when it’s producing power, but power from the battery/distribution panel doesn’t flow up into the solar system.

      Simply put, you are splicing into the wiring between the battery and power distribution center, adding another power source (in addition to the battery power).

      While being really simple in execution, It may be a tough concept to wrap one’s head around because electricity is one of those things that you don’t see so it can be a bit difficult to understand.

      I hope that helps!

  • How simple would it be to install an inverter for use on the exterior of this setup, and what additional. Balance of systems are required?

    • Hi Steven,

      I’m not sure what you mean by ‘exterior of this setup’ and ‘balance of systems’.

      Installing an inverter requires using the correct (heavy gauge) wiring from the battery to the inverter, appropriate circuit protection (fuse), as well the correct wiring into the existing 120-volt outlets (if that’s the route you want to go).

      Adding an inverter is beyond the scope of this article as it’s not something I’ve ever done. I’ve now done two similar solar installations – on Kelly’s rig and on mine (just recently) but didn’t add an inverter to either installation as it’s not something either of us need.

      You will want to consult with someone VERY familiar with RV inverter installations to plan out your exact installation.

    • Hey Judie,

      Ah, sure does look brown, doesn’t it? Believe it or not that Dicor started life as being white.

      The pics you are referencing were taken about 6 months after the installation. What you are seeing is the dust/dirt from living life down dusty Forest Service Roads and other non-paved trails. Since we boondock the vast majority of the time, our rigs (including the roof) tend to never stay clean.

      Dicor is a bit sticky to begin with, so it will attract dust and dirt. The only time Dicor will be pure white is the day you install it…

      Great question! Thanks for asking and reading!

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