RV Electrical Upgrade: Part 2 – Battle Born Lithium Batteries & Victron Inverter

Mon Nov 19 2018

In Part 2 of our series on upgrading the electrical system in our RV, we're going to be jumping straight in with the biggest components - the Battle Born Lithium batteries and a new Victron MultiPlus inverter / charger. We'll also be laying the groundwork needed for installing the remainder of the system later on in the series too.

RV Electrical Upgrade: Part 2 – Battle Born Lithium Batteries & Victron Inverter

In Part 1 of the RV Electrical Upgrade series, we introduced why we needed to upgrade the electrical system in our RV, what our new requirements are, and some of the constraints we had imposed on ourselves. If you haven't read that post on our Introduction & Goals, I recommend doing so before jumping into this post.

This post, and the next ones in the series, will be looking in detail at the different components we will be adding. We will discuss how they contribute towards our system goals, why we chose those particular components, where we sourced them, how much they cost and how we installed them.


It's worth mentioning that everything was selected on the basis of its merits from our research and purchased at the best price we could find.

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Diana and I did this entire install ourselves - right from the design of the system, buying the parts and installing everything. We made loads of mistakes along the way, and we probably (OK, definitely!) took longer than a professional installer would have done. I've structured this blog series in an order that makes logical sense to guide you through, but it's not exactly the order we installed things in - for example, we did the truck modifications (oooh, spoiler!) before anything else because it was convenient to do.

That being said, the bulk of this install took the two of us working 7 (long!) days almost non-stop - that's just the install, not including the time spent planning and designing. Even though it was over 90°F in Texas in August when we did this install, we had to have the power turned off for long periods during the install for safety - that meant no air conditioning!

For context, I've seen an estimate from a well-regarded solar equipment supplier and installer for a system not too dissimilar to ours - they quoted over 60 hours of labor costing over $7,000! So at the very least, we've saved $7k in labor costs alone.

Disclaimer: Mistakes in the electrical system can cause fire, injury or even death. If you have any doubts about working with electricity in your RV, consult with a professional electrician.

We've also been able to add features I don't think a "typical" install would have included, and we've learned so much about our RV along the way - that, to me, is worth so much more!

Goals of Part 2

I think it's always helpful to have clear and explicit goals for each step in the install. In this part, we're going to get stuck right into some big juicy tasks - preparing the area for all the components to fit in, then installing the Lithium batteries and inverter / charger. We'll also be adding the necessary wiring, fuses, switches and busbars (the what?!), as well as installing the battery monitor and control panel.

We won't be connecting this system into the RV yet though. For now the only connection we'll be making between the new batteries and the RV is the grounding cable - this is for safety. Everything in this post can be done without disconnecting shore power or your existing batteries. We deliberately chose to do it this way so we could continue to live normally in the RV whilst we worked on it (yes, we really wanted the Air Conditioning!), and so we could take our time to double (and triple) check everything was done properly rather than rushing to get power back on.

By the end of this blog post, you'll have a completely brand new, standalone electrical system in your RV consisting of 2 different circuits - 12V DC and 120V AC (albeit with no outlets). This is enough to let you test everything is working correctly before making changes to your existing RV electrical systems.

The remainder of this post is broken down into 2 big sections. First, we'll go through an explanation of the parts we're using and why, concluding with a full parts list. Second, we'll go through the install itself - starting with preparing the area, and then fitting all the components. Let's get started!

Explanation of Parts

Which batteries to use, why, and how many?

In Part 1, we decided that we need 200-400Ah of usable battery capacity and that the only way to provide this within our weight and space constraints would be to go with Lithium batteries as opposed to Flooded Lead Acid. Although the upfront cost of Lithium batteries is much higher, for full-time RVers like us, the Total Cost of Ownership (TCO) is actually lower as Lithium batteries last for more cycles. We also like the better safety (no acid anywhere) and zero-maintenance aspects of them.

After many hours of research (and countless electrical schematics) we chose to go with Battle Born to provide the batteries. Their 12V LiFePO4 battery is a drop-in replacement for a normal 12V battery. Its integrated Battery Management System (BMS) allowed us to hugely simplify the installation design since it handles keeping the battery within voltage, current and temperature tolerances - something we would have had to do ourselves had we gone with raw Lithium cells.

As for how many, we settled on 300Ah (3x 100Ah batteries) for two reasons. First, after lots of sketching out different layouts for the components under the bed, 3 batteries was much easier to accommodate than 4 batteries - we could have done it, but it would have been very tight.

Second, the battery spec sheet shows each battery can provide 100A continuous current, with a 200A surge for 30 seconds. We would be coupling these batteries with a 3,000W inverter (more on this later) - even assuming perfect efficiency (ha!), that would need 250A at 12V. Since you can't have half a battery, that means it would need at least 3 batteries to satisfy the current demands of our inverter at full power.

So that really settled it - we needed at least 3 batteries to power the inverter, and didn't have space to easily accommodate more than 3 batteries. I guess 3 batteries it is then! If we had more space (and budget - the batteries are $950 each!), I think I'd have probably gone with 4 batteries ideally - for the dry camping we tend to do, the extra capacity would have been useful.

3 Battle Born Lithium Batteries
Our 3 Battle Born Lithium LiFePO4 batteries - it would have been a squeeze to fit 4 in!

An added benefit of 4 batteries would be a little more headroom on that current limit of 100A per battery. We have tripped the BMS a couple times due to this limit, but it took very specific conditions to do so - specifically when our inverter jumped took over when our shore power died during a high-power period, and the draw was just a little over 300A for more than 30s.

Which inverter and why?

I've already revealed that we chose a 3,000W (3kW) inverter, so let me share more details and rationale. The inverter we chose was the Victron MultiPlus 3kVA 120V (aka the Victron MultiPlus 12/3000/120).

Let's start with why we chose this size of inverter. Our RV is a 30A rig - meaning we have a single-phase AC circuit that can deliver up to 30A of power to all the appliances in our trailer, and 30A at 120V is 3,600W or 3.6kW (or in Victron-speak, 3.6kVA). As long as we don't try to use the electric water heater, microwave, AC and Instant Pot all at the same time - this is plenty for us! But we wanted to be able to use these appliances (we paid for them, after all) when dry camping, since that's how we plan to live in our RV most of the time.

Making the jump to a 5kW inverter would have increased cost, weight and space, plus the extra power wouldn't have been usable without more extensive upgrades to other circuits - the master breaker in our AC panel would trip at 30A. Sacrificing 600W of headroom to go with a 3kW inverter made the most sense and was a compromise we were happy with.

So why Victron? Throughout much of the research, I had been planning to integrate a Magnum inverter, but I changed to Victron towards the end. Why? Well, Victron has built an ecosystem of parts that play nicely together - inverters, solar charge controllers, battery monitors, and more. The system works seamlessly, but you pay a price premium. I tend to be weary of buying into an ecosystem like this - what happens if you want to add a component that they don't manufacture, for example?

As it turns out, Victron was a superb choice for us. They are midway through a huge exercise to open-source their software, giving unparalleled access to configure and integrate with their systems. For a complete geek like me, this was invaluable, and something that differentiated Victron from Magnum - their inverters were otherwise almost identical on paper in terms of size, performance and capability. Look out for future blog posts on some of the cool stuff we've already done using this, and some of our plans to build more on top of it.

How will we monitor and configure the system?

OK, I'm just going to come out and say this - we splurged here. If you're going to buy into the Victron ecosystem, you might as well go all-in - so we did. If you want to save some money, it's easy to save here. But here's what we did and why.

Monitoring the State of Charge (SoC, i.e. what % are the batteries at) for Lithium batteries is a little trickier than for conventional Lead Acid batteries or AGMs. The challenge is that the voltage stays very constant throughout most of the battery's charge profile - unlike in other batteries where the voltage drops as it discharges. This means you can't just measure the voltage to measure the State of Charge - although it's actually great for your appliances which have a much more stable voltage regardless of the battery SoC.

Instead, you have to keep track of how much current has flown into and out of your batteries - a method known as Coulomb counting, the same method your laptop uses to keep track of its charge. To do this, we chose to use Victron's BMV-712 - a bells & whistles device that keeps an eagle-eye on your battery and makes all the information available on your iPhone or Android via Bluetooth. In hindsight, I'm super pleased we splurged for this - it's great being able to check the battery health from the truck, for example. The BMV-712 comes with a Shunt, a small device you connect between your battery's negative terminal and the rest of the circuit - this is what counts the Coulombs for you.

However, our biggest extravagance was probably the Victron Color Control GX (CCGX). This color-screen panel allows you to configure everything about your Victron electrical system, as well as checking real-time performance of everything too! Since they've released the software as open source, it's actually possible to get this running on a Raspberry Pi - maybe an exercise for another day! Although expensive it serves not only as the one-stop configuration point for us, but is also the key hub for accessing all our data - we can configure our system remotely from wherever we are, and export the data for our own geeky tendencies.

If your needs are more modest (e.g. turning on / off the inverter, etc), you may find Victron's Digital Multi Control 200/200A GX is more appropriate!

How will it all be wired together?

Let's talk about wiring. It's actually something of a misnomer to describe your 12V circuit as low power - a better moniker is low voltage. Why? Well remember the relationship between power, current and voltage (Power = Current x Voltage) - for a given power, if the voltage drops the current goes up Powering your electric water heater might draw 1,500W - at 120V AC, this is 12.5A but at 12V this is 10x higher at 125A.

"Thanks for the Physics lesson, Matt, but why does that matter?"

Well, without going into the detail behind it, more current in a wire means you need a thicker wire - much thicker! A thinner wire means more resistance, creating more loss of voltage (and hence power), more heat in the wire, and ultimately the wire will melt - which is exactly how a fuse works.

In fact, a wire to carry 125A needs to be over 3x larger in diameter than a wire to carry 12.5A All this is to set the stage that we're going to be dealing with some thick wires here - really thick. Search for "12V Ampacity Chart" on Google and you'll find lots of tables that show how thick your wires need to be.

Remember how in Part 1, I said there aren't any electrical codes for RVs and I used the Marine / NEC codes instead? This topic is a good example - and one where I chose to over-engineer our solution. Electrical loss in the wire is not only a safety issue, but also reduces the efficiency of the system - not good in an RV where we're trying to conserve power. We therefore chose to keep the loss as low as possible (almost always below 3%, the guidance for trunk wiring in a house or critical marine systems) - use a power loss calculator to check this.

For this reason, we chose to run 4/0 cable for all the high-power interconnects in our system - i.e. between the batteries, switches, fuses, busbars and the inverter. This is just about the thickest cable you can easily get your hands on as a consumer, and is often sold as Welding Cable. At nearly 11/16" thick, this stuff means business! Size is measured according to the American Wire Gauge (AWG), where a lower number means thicker cable - and 4/0 means 0000. So 4/0 (0000) is thicker than 2/0 (00) is thicker than 2 is thicker than 4 etc.

We sourced ours from a company called TEMCo Industrial, based out of Fremont, CA but shipping nationally. We chose them because they were local to us (we lived in Fremont, CA) but have been exceptionally pleased with both the product and service. Regardless of where you buy from, you want high quality cable - specifically I'd recommend high strand-count copper to keep resistance low and flexibility high. The 4/0 cable we bought from TEMCo has 1,950 copper strands and is incredibly flexible given its thickness!

As a rule, we always used the thickest cable we felt we could - almost everything is 4/0, 2 or 6 AWG. We also tried to mainly use red for positive cables, and black for negative. This isn't necessary, and makes it harder to plan how much cable to buy, but makes it more obvious which cables are negative and which are positive. If you don't do this, at the very least use colored heat shrink or tape to indicate the cable types - some people also use blue or another neutral color for the cables to avoid confusion.

Building the cables

Buying the cables was just the start. They then need cutting, the ends terminating with connectors, and then protecting. We used a set of heavy duty cable cutters to cut the cables, and a 16-ton Hydraulic Wire Crimping tool (!!!) to crimp terminals on the end.

Cutting the cable
It takes a lot of effort even with these cable cutters to cut through the thick 4/0 cable.

We chose to use tinned copper ring terminals (these are the highest quality ones) that we bought from TEMCo, and we bought multiple packs sized correctly to fit the components we needed - correctly sized ring terminals is a marine electrical code requirement, and makes a lot of sense!

Stripping the cable
Stripping the cables is easy with a sharp knife - the TEMCo cable is lined with paper which helped avoid cutting the copper strands inside.

Once each end of the cable was cut, stripped (easy with a knife if you're careful) and crimped with a ring terminal, we added used adhesive-lined heat shrink to seal the ends.

Crimped connection
The 16-ton hydraulic wire crimping tool gives a very secure and uniform crimp. If you cut through the connection you'd find that the wire had been cold-welded into a single copper piece! I used a file to smooth the sharp edges before putting the heat shrink on.

This strengthens the connection even more, adds protection, and limits the exposed area of the conductor. Building the cables was a slow process, but the end result is a system that not only looks professional, but most important is safe and durable for life in an RV.

Adhesive lined heat shrink
We used a heat gun to seal the ends of the cables with adhesive lined head shrink, forming a really secure connection.

Lastly, for any wires that had to run somewhere that they might chafe (e.g. through a hole in the floor), we encased the wires in split loom - a protective plastic tubing that's split down one side to let you put the wire in.

Switches, Fuses & Busbars

Although much of the electrical upgrade may sound complex, for the most part it uses simple components. I've lumped together these last few components, but this shouldn't diminish their importance. We sourced all of these from Blue Sea Systems, a manufacturer of marine-grade electrical components renowned for incredibly high quality - they cost more than other brands, but the quality is worthwhile in my mind.

Our design included 3 switches, all of which needed to switch very high current. We chose the Blue Sea System e-Series 9003e Battery Switch which is rated to 350 Amps. It's an absolute beast, and I have no doubts about its quality.

There are several fuses and breakers in our final install, but for Part 2 there's just one we need to install - the so-called Catastrophic Fuse. This is a fast-acting fuse, sometimes known as a Terminal Fuse (or T-Fuse), installed as close to the battery as possible. Fuses are there to protect not just your devices, but also your wiring, so when sizing a fuse it needs to be lower than the rating of your wires and any other components. For our design, we went with a 400Amp fuse, but you should size accordingly for your install. Specifically, we chose the Blue Sea Systems 400Amp Class-T Fuse, mounted in a Blue Sea Systems Class-T 250-400A Fuse Block with Insulating Cover - clean, professional and safe install.

Lastly, are the Busbars. If you're not familiar with these, they're just a metal bar with very low resistance that allows you to connect multiple cables together without stacking connectors. Marine code limits the number of connectors on one post anyway, but I find it easier to install, cleaner and safer to have as few connectors stacked as possible. Our install has two busbars on the 12V circuit - one for positive (+12V), and one for negative (0V, ground). We used 2 of the Blue Sea Systems 4 x 3/8" Stud 600A Powerbars - more current capacity than we need for now, but a solid device.

As a brief aside, if you're not familiar with electrical engineering this may sound strange, but the negative side of your electrical circuit (and anything attached to it) should be connected to ground - the physical, earth ground that you're standing on. In an RV, we do this by connecting everything to the chassis of the RV. Later on in the install section, we'll connect a cable from our ground bus bar to the RV chassis.

What this means is that (if you've installed it correctly), it's completely safe (and encouraged) to touch the negative side of your battery - many electrical devices will ground the metal casing, in other words, run a wire from the metal case to the 0V ground connection.

I mention this now, because it matters for busbars. If you touch the ground busbar, absolutely nothing will happen - you will not get a shock. You'll also be fine if you touch the ground bus bar with one hand and touch anything else in the RV (except the positive wires!) at the same time. But this isn't true for the positive busbar. If you connect anything (including yourself) between the positive busbar (or any other positive part of the circuit) and ground (either the ground bus bar, or any exposed metal on the RV) you will create a short circuit - electrocuting yourself or worse. Don't do it.

For this reason, we also added a Blue Sea Systems 4 Stud Cover to our positive busbar, reducing the chances of something coming into contact with it. We left the ground busbar exposed. Safety first.

Parts List

Below is a summary of the components we used for Part 2 of the installation. Some of these were purchased in larger quantities because we would be using more later - you may need more or less depending on your install.

We did purchase a bundle through Battle Born that included several components. This included the batteries and several other components, marked with an asterisk (*) below, but check out the packages to see if you would save money going down that route. The bundle included several components we didn't need but figured we'd hold onto as backups or sell later - we ended up spending a little under $300 for some spare components worth more than that.


These are the major components that our system needed.

ItemQuantityLink & Unit Price
Battle Born 100Ah 12V Lithium LiFePO4 Battery (*)3$949.00 @ Battle Born
Victron MultiPlus 12/3000/120 Inverter / Charger (*)1Check Price
Victron Color Control GX (CCGX) Monitor1Check Price
Victron BMV-712 Battery Monitor (*)1Check Price
Blue Sea Systems e-Series 9003e Switch3Check Price
Blue Sea Systems 400A Class-T Fuse1Check Price
Blue Sea Systems Class-T Fuse Block1Check Price
Blue Sea Systems 600A 4x 3/8" Stud Powerbar2Check Price
Blue Sea Systems Powerbar Cover1Check Price


I've grouped together all the cable, terminals, and heat shrink here. The unit price may be cheaper if you buy more and vice versa. Similarly, I've not included things like screws that we already hadn't and didn't need to buy.

ItemQuantityLink & Unit Price
TEMCo Welding Cable - 4/0 AWG 50% Red 50% Black (20 ft)1Check Price
TEMCo 4/0 AWG 5/16" Ring Terminal - Tinned Copper (10 pack)1Check Price
TEMCo 4/0 AWG 3/8" Ring Terminal Lug - Tinned Copper (25 pack)1Check Price
TEMCo 1" Marine Heat Shrink Tube Adhesive Lined Black (4 ft)1Check Price
TEMCo 1" Marine Heat Shrink Tube Adhesive Lined Red (4 ft)1Check Price
Heavy Duty Chrome Footman's Loops (pack of 6)1Check Price
Utility Strap With Quick-Release Buckle (pack of 4)1Check Price


I'm assuming you have basic tools such as a hammer, socket wrench, screwdrivers, etc. These are the special tools required for this project.

ItemQuantityLink & Unit Price
Wiss Industrial Hand Tool Cable Cutters1Check Price
16 Ton Hydraulic Wire Crimping Tool1Check Price


As you'll read shortly, we also had to reinforce the space under the bed where we would be installing this system. Depending on where you are installing your system, you may or may not need something similar. We already had a few off-cuts of wood so we used a few scraps up as well. You can also get cheaper lumber too, but we wanted knot-free, clean, square-edged lumber to make our lives easier.

ItemQuantityLink & Unit Price
Lowes 15/32" Common Pine Sanded Plywood (4ft x 4ft)1$18.23 @ Lowes
Lowes 2" x 2" x 96" Pine Board1$11.32 @ Lowes
Lowes 1" x 2" x 96" Pine Board1$5.73 @ Lowes
Rustoleum 15 oz. Black Truck Bed Coating Spray1Check Price
Everbilt 12 in. x 8 in. White Return Air Grille2$6.85 @ Home Depot

Total Cost

Including the special tools, this phase of the install cost a total of around $6,000 (ignoring our extra bundle cost). Certainly not cheap, but this is a top-end system built with very high quality components. Let's move onto the build itself.

Preparing the area

Before we could start the install itself, we had to prepare the area. Our big consideration was weight, but also access - making sure we could get wires where they needed to go later.

Strengthening the space under the bed

Under the foot of the bed in our Outdoors RV 21RBS is a storage space and some drawers. The drawers are at the bottom, accessed from the sides and the space on top is accessed by lifting the foot of the bed. It's this upper space we wanted to use to install our electrical system.

Diagram of the shelf
We used our new dry-erase fridge-freezer whiteboard to sketch out our plans.

I don't imagine this is what Outdoors RV had in mind for this space - the shelf that sits above the drawers is made of thin hardboard, presumably for holding pillows, blankets and the like. Certainly not a 40lb inverter, 87lbs of batteries and assorted other electrical paraphernalia. We thought at first about just putting a sheet of plywood on top of the existing shelf, hoping the shelf supports around the sides would hold the extra weight. In the end, we decided to go all-in - remove the existing shelf, strengthen the supporting framework and install a solid shelf on top.

We cut the shelf into 4 pieces and pulled them out one by one. Even so, it was hard work!

I'm very glad we did! The thin hardboard shelf was resting on a sparse matrix of 1x1 struts - although I can only assume there was a special offer on glue and nails near the factory that week as it took us a couple of hours to pull it all apart!

This stuff put up a real fight!

Using some 1x2, some 2x2 and plenty of screws and glue (to pay homage to the factory install), we built a truly solid scaffolding frame underneath where the new shelf would go.

Strong frame
Our new substructure is much stronger than what was there before. To test it, we each tried climbing inside and there was no sign of movement even with all my weight on it.

Adventurous Tip: Make sure your trailer is perfectly level when doing DIY if you're planning to use a spirit level.... Yeah, you understand.

Fishing tape to the front bay

In our RV, like many others, there is an electrical junction area located (hidden?) underneath the trailer at the very front, just behind the tongue. Lots of things converge here, including the tongue jack, the batteries, 7-pin trailer connector, solar wires, etc. Over the course of the entire install we would run several wires here, but for now we just wanted to run a fish tape through so we could use it as a wire pull.

Very carefully, starting with a small drill-bit and moving progressively towards a hole-cutting bit, we cut a 3" hole in the floor of the RV, right in the middle, as close to the front as we could. We were being careful to avoid drilling through any wires that might be there - we knew a wire run was pretty close by because we could see it disappearing in that direction from the front.

What a mess!
Our trailer was a complete mess whilst we worked on this project. I think I may have invented some new yoga positions trying to work in there too!

With the hole cut, we used a fish tape to get between the front electrical junction area and our space under the bed. When the fish tape was through, we used it to pull through a long piece of spare electrical cord to use as a wire pull for later.

Adventurous Tip: Make sure you keep at least 6ft on either end so you can pull wires back and forth as necessary.

Installing the component shelf

We cut a piece of 1/2" plywood for our new shelf, and glued a second piece on top in the middle since this is where most of the components would be screwed down and it's much easier to screw into a 1" piece of plywood! We cut a 3" diameter hole at the back for wires to down through (more on that later), and glued / screwed three small pieces of wood on the right hand side to act as a guide to hold the batteries in place.

Gluing the shelf
We glued and screwed down the middle section to make it easier to attach our switches, etc to later.

Even though we had a dimensionally-accurate diagram of the component layout, we took our time and test-fitted pieces several times. Remember, measure twice (or thrice) and cut once!

Test fitting
Taking our time to clamp things up and get everything in the right place.

I spent a long time going back and forth on the finish - I knew I didn't want unfinished plywood because, well, it would look unfinished. A common approach is to use speaker cabinet lining - the grey felt-like material. However it's almost impossible to find a flame-resistant version of it, and the thought of the lint being pulled through the inverter, etc is not something I felt comfortable with. In the end, I chose to use spray-on truck bed-liner. It's cheap, it's clean, it looks smart, it's easy to apply, and it's crazy durable. We're really pleased with how it turned out.

Spray on bed-liner
We used spray-on bed-liner to give the shelf a really strong and durable finish.

We took our time cutting the shelf - it was such a perfect fit that it sits in place with no wiggling at all, firmly in position without bowing the walls out. The fit was so good we chose not to screw it down - much easier to get underneath should we ever need to.

Cutting out vents

In an ideal situation, you'd install the inverter in a big open space with plenty of ventilation - something we're short of in our small travel trailer. We did adhere to the manufacturer's guidelines to keep a 4" (100mm) space free around the inverter on all sides. Research showed that the airflow of the inverter pulls air in at the bottom and out at the sides near the top. To accommodate this, we laid out our install so we could position vents accordingly.

Vent covers
Two vents in the end and side of the bed allow airflow for the inverter.

We used two 12" x 8" air vent grilles and cut spaces for them in the sides of the bed with a hand saw. These let plenty of air ventilate into the area and we haven't had any problems with the inverter overheating.

Installation procedure

Before we jump into the install, let me give you some advice - test fit your components repeatedly. Yes, I know they're heavy, bulky and difficult to move, but they're much harder to move when they're bolted down! Take your time, measure twice, and cut once - that applies to cables too! By doing this, we managed the entire install without one wrong cut on a single cable - I'm pretty proud of that.

Mounting the batteries

We started with the batteries as they were the item over which we had least control of the positioning. We set the batteries down, aligned tightly in their wooden guides. Using the Footman's loops (that was a new term for me!) on both sides of the batteries, we added some sleek but sturdy tie-downs - those batteries ain't going nowhere!

With the batteries mounted, you can now cut and crimp all the cables. I'm not going to talk through cutting every cable in the install, but here's the general process we followed for every cable:

  1. Select the right size ring terminal and crimp it on one end of the cable with the 16-ton hydraulic crimping tool;
  2. Use adhesive-lined heat shrink to seal the end up securely;
  3. Hold the new ring terminal against where one end will go, aligned in the direction it will best fit on;
  4. Use a permanent marker to mark how long to cut the cable and which orientation to put the ring terminal (it's much easier to install these thick cables if the terminals are lined up the right way!);
  5. Cut, crimp and heat shrink the other end of the cable.
Oven gloves
Look, when you live in a small RV, you work with what you have. These cat-themed oven gloves made it much easier to put some real force into those cable cutters!

It's a slow, painful process, but the result looks great and is super secure. As an example, the battery interconnect cables we cut are such a perfect fit and are so thick that even without the battery straps in place, the cables alone stop the batteries from wiggling at all!

Once you've got all the batteries fitting and the cables cut correctly, remove them. Yup, take them out. That's a lot of power and several uncovered live terminals sitting there waiting for you to touch across or put that all metal tool (which you definitely shouldn't be using) across them. It's much safer to take the batteries out until you've finished installing the rest of the components.

Locating the inverter

The inverter is next - and this one can stay in place, I promise! Our layout had this on the opposite side from the batteries to balance out the weight on the shelf. Position it in place, ensuring it has the necessary clearance around it, and screw it down to the shelf below - easy. We'll come back to the wiring shortly.

Installing the switches, fuse blocks, bus bars and wires

This part is where you can get a little freeform. After doing the battery interconnect wires, you should have a sense for how much flexibility they have. I started in the bottom right corner of our layout, and worked my way up and left, cutting the wires and making sure they fitted before screwing things down. Once I was happy that the wires weren't bending too much, weren't stressing anything, and weren't going to rub on anything, I screwed things down.

Dry fitting
I dry fitted the components before screwing things down, and cut out bits of cardboard the size of some components I would be installing later.

One very important thing to note - install the fuse block but do not install the Class-T Fuse itself (aka Catastrophic Fuse). This is one of the last things we'll do once we're happy with everything else. On a similar note, make sure all switches are turned off as you install them - the batteries aren't connected yet, but it's good to keep things turned off in case you forget to check later.

You should have a schematic that you're following, but there are two wires I want to call out as important. The first is the ground wire from the inverter to the ground busbar. Although there is already a negative wire that runs to the inverter, there is a separate grounding wire as a backup - don't forget this one.

The second wire is the ground wire that runs from the ground busbar to the RV chassis itself. This is what will ensure that your new circuit is grounded at the same potential as everything else in the RV - until you do this, the ground of your new 12V circuit will be floating at a different potential which is a bad thing. We ran this wire to the front electrical junction area and grounded it onto the chassis there.

Grounding the system

This is one of the most important steps to get right. You need to ensure that you have good electrical contact between your grounding wire and the chassis. The factory ground lug on ours looked OK, but I've seen plenty of examples of loose, rusty connections. I played it safe and created a brand new ground lug.

Fortunately the process is simple. Drill a hole through a piece of chassis you can access on both sides, the right size for a bolt to fit your ring terminal. Use a wire brush attachment on your electric drill or Dremel to scrape off the paint on both sides around the hole. Install a nut and bolt with two washers and a split lock washer on the nut side (not star washers, they actually have less surface contact than a split lock washer used correctly). You can then attach your ring terminal with a nylon lock washer, and spray the entire thing with some CRC Battery Terminal Protector to stop any corrosion. That's a super strong and durable grounding point, almost certainly better than the factory one.

BMV & Shunt

Let's move onto some easier things. With all the other major components installed, you should now be able to install the shunt, up near the negative battery terminal. In addition to sitting inline with the negative side of your circuit, the shunt has two other cables - a thin positive wire that you can attach to any convenient positive part of your circuit, and a data cable that will connect to the BMV.

Following the instructions that come with the BMV, we cut a hole for the battery monitor in the end of the bed, and mounted it. We then connected it to the shunt with the data cable.

Installing the Victron BMV-712 and CCGX
Taking my time to cut the holes for the Victron BMV and CCGX in the end of the bed.

It's worth noting that the BMV will lose count of its Coulombs if it loses power. In practical terms, this means that if the BMV loses power for any reason, the battery State of Charge will reset to 100% - pretty annoying, and something I hope Victron can fix! We had this happen when our BMS kicked in to protect the batteries from over-current discharge. In a later part, I'll show you how to wire in a 12V UPS to keep the BMV powered, but for now, keep it simple and connect it up to 12V via the fused lead provided.

Wiring up the CCGX

Installing the CCGX is, for the most part, very simple. Cut a hole according to the instructions, and mount the CCGX in place. We installed ours next to the BMV in the foot of our bed. Our CCGX didn't come with a power cable, so you'll need to connect it up to power (positive and negative) with a fused power lead.

The CCGX accepts two more connections in our install. The first is a data cable (that's just a standard network cable) to the inverter - instructions are included with the inverter.

The second is a wire connecting it to the BMV - this is important as it gives you more accurate SoC readings on the CCGX. You have 2 options here. Option A is to buy a 0.9m VE.Direct cable to connect the two devices that sit about 3" apart. I chose Option B - to buy a 15-pack of 8" long JST PH 2.0mm 4 Pin female cables and solder two together to make my own, following the instructions here.

The last thing to add is that, if possible, you want to connect the CCGX to your router via an ethernet cable - this lets you take advantage of Victron's VRM portal, and remotely manage your system, as well as a host of other benefits.

Victron BMV-712 and CCGX
The Victron CCGX (left) and Victron BMV-712 (right) looking very snazzy in the end of the bed!

Thinking about it, I'll probably do a full-write up on the CCGX at some point as I've learned so much about it.

(Re-)connecting the batteries & installing the fuse

OK, we're on the home straight now. Make sure all your switches are turned off and the fuse hasn't been installed yet. Double check all the terminal nuts are tight.

You can put your batteries back in, secure them in place, and build 2 cables to connect them in on the positive and negative sides. Now, with the main battery switch definitely turned off, install the Class-T fuse. Your system is now electrically live, except for the switches being off.

Install at the end of Part 2
The finished install, looking good! (Actually, we took this photo during a test fitting before we installed the BMV-712 and CCGX on the front.)

Using a multimeter, take voltage readings across different points in the circuit, making sure that you have 12V (it'll actually be around 13-14V) where you expect to, and the same with 0V. Once you're happy, turn on the battery switch and check more connections.

The last step is to turn on the inverter. One of the awesome things about ordering our inverter through Battle Born is that they preconfigured the system for us. If you ordered yours elsewhere, then you'll need to follow Victron's documentation to configure it.

At this stage the inverter won't be powering anything, but you just want to see that it turns on when you, erm, turn it on. Once you're happy everything is working, turn everything off again. You're done with Part 2!


Gosh. That was a lot! If your experience is anything like ours, I've just condensed about 4 days of work into 1 blog post. Still reading? Go get yourself a drink, you've earned it!

But we've accomplished a lot here - the bulk of the upgrade, the most complicated part, is now done. Although there's more to do, from here on in, each project is smaller and standalone.

I remember when we reached this stage of the install, we were super pleased. We were able to throw out lots of boxes that had been cluttering up our space, the install looked really professional, and we felt confident in it. Good times. As I'm writing this post, that was over 3 months ago now, and we haven't had any issues at all with it.

Next steps

So, what's next? Well, next in the series, we're going to be looking at one of the most novel parts of our electrical upgrade - using the truck as a high-power charger when we're hooked up. Stay tuned for that one - everyone who has seen our install so far has been asking for the write-up on how we installed the truck charger.

Then, in Part 4, we'll get right back into it and connect this block of components into the RV, removing the factory battery, installing an EMS and connecting the inverter into the main AC panel - very exciting!

Future blog posts will look at other things you can add to the install, such as solar panels, an upgraded 12V distribution panel and more.

So stay tuned, and if you enjoyed this blog post then be sure to subscribe to our email newsletter for lots more great information.

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