Off-Grid 1979 Airstream Electrical System

We spent some time with Kyle and Olivia Brady of Drivin’ and Vibin’ helping with their extensive remodel of their 1979 Airstream Argosy trailer. As part of the project, we helped build an entirely new electrical system that would be optimized for off-grid comfort.

This meant utilizing a large battery bank, a hybrid inverter, solar panels and a monitoring system.

*Check out the complete renovation project in our blog post that summarizes all the work that was done while we were there:
Read the Blog Post: Drivin’ and Vibin’s Airstream Argosy Renovation

Electrical System Design

As with any project, understanding and designing within the project limitations is key. Since this trailer is smaller and has a lower weight capacity, weight and space considerations were a big part of the system design. Cost is always a consideration and getting an idea of total installed cost is important up front as well. Once we had a good idea of the system we were wanting to install, where, and how, we got to work. Olivia had a general design for the layout of the trailer and knew approximately where we were going to mount lights and receptacles. Installing the electrical system started with running wires in the walls while they were taken apart. Stranded wire was used through the RV because many of the bends exceeded that of code for Romex installations. We could have used Romex in some places but we purchased stranded wire in bulk and used it everywhere. DC power was wired with 10AWG or 12AWG black and red, and AC wire is white for neutral, black for hot, and green for ground in 12 AWG.

Once the wires were pulled and the walls were back up we got to work installation the rest of the equipment. Below is a schematic of the entire system we installed and includes everything we will talk about in this post. Click the image to download a high resolution copy. Just below and at the bottom of this post are also lists of all the equipment used in this system.

Click Here to download a copy of the schematic above Download

Equipment & Components List

We’ve compiled a list of the main equipment we used on this project into an easy-to-see Kit.
Click Here for the 30A Off-Grid Electrical System Components Kit

Batteries

Batteries are critical to an off-grid system. The more power you can store, the longer you can go without generator charging or solar. It was critical for us to get as much capacity as we could within the limitations of our project and it made most sense to install lithium ion batteries. Kyle and Olivia chose to install 5 – 100Amp hour Battle Born lithium batteries because they have a very high energy density, meaning they are lightweight and will take up less space than lead acid. Lithium batteries also last much longer than lead acid and have no off-gassing so they can be installed inside. The advantages are so huge over lead acid that I think we will soon see most of the industry switching to lithium batteries. The Battle Born Batteries have a built in BMS which makes them very safe. I had the opportunity to speak with the owners of battle born a while back and put a video together about it that you can watch here.

Interview with Battle Born Batteries CEO and COO - Lithium Batteries Technical discussion

Watch this video on YouTube

We installed the batteries under a seating area inside the RV. It was critical to keep them inside because the only downfall of lithium batteries at the moment is that they cannot be charged below freezing. Keeping them inside should keep them warm.

The batteries were installed all in parallel to keep the voltage the same. You will notice that we used two 1/0 cables per battery lead. We did this at the sake of cost because we already have lots of 1/0 cable and paralleling them is an acceptable way to get the ampacity. One 4/0 cable would have worked as well. While the Battleborn batteries do have a BMS that will limit the current to protect the batteries, you do not want to ever short the batteries out. Be very careful when connecting up batteries as it can be very dangerous!

battle born batteries installed in airstream

12V distribution

After connecting the batteries the positive cable first passes through a main battery disconnect. This disconnect allows the entire system to be taken offline to work on downstream components. Keep in mind that if a battery charger is running, throwing this switch may not kill 12V to the system and the battery charger would have to be taken down as well to work on it. Always check and double check for voltage before working on any components.

After the disconnect switch, the power passes through an ANL fuse block with a 350A fuse. This fuse size was based on the components in the system and sized to 130% expected current. Fuses are very important components that protect the system if a short occurs. Without a fuse, a short could cause a fire.

Off the negative side of the battery bank everything first passed through a victron BMV712 500A rated shunt. The shunt measures battery voltage and all the current passing into and out of the battery and connects to a remote display. The display provides information like battery state of charge (SOC), voltage, current, Amp Hour usage, and estimated run time on the batteries. This is a critical device to properly managing a system like this to know how much power you have stored and when you might need to fire up a generator. I really like this shunt because it has built in Bluetooth that enables you to easily check battery state of charge on your phone and program the unit.

The shunt that all power passes through to measure current

The Battery monitor display screen BMV712

The battery disconnect, fuse and shunt were installed as close to the batteries as possible in the same compartment. After connecting to these devices the cables passed on to the next compartment where most of the electrical equipment is installed. This compartment is the bottom of a closet and will be closed up once complete. On the front of the compartment we installed equipment that needs to be accessed like the BMV712 screen, Fuse and AC panel, AC transfer switch and inverter enable switch. We will go over the rest of these components in a bit.

Main Electrical compartment located at the bottom of a closet

Control faces that are accessible

Once in the electrical compartment the cables immediately land on a set of bus bars. These busbars distribute power and allow multiple pieces of equipment to be connected to the batteries and help keep the install clean. Connected to these busbars is the inverter, the solar charger, and the the lower power DC fuse panel for powering the rest of the RV.

The Busbars

Back of the PD4000 unit with the leads connected

Fuses in PD4000 unit

The DC fuse panel we used was integrated into a Progressive Dynamics PD4000L power center. This unit combines an AC breaker panel, DC fuse panel and battery charger into one unit.

We connected the positive DC input leads to the busbar which powers the built in fuse panel. 1-20A blade fuses can be installed and then pass power to the pre-installed and labeled output leads on the back of the unit. These leads we then connected to the DC wires we had run in the walls previously and out to equipment in the RV, such as the water pump, lights, fans, jacks and any other equipment that required 12V DC. As the PD4000L did not have a negative bus, we installed our own negative busbar that we brought all the leads back to. We connected this to the negative battery busbar so all the power can flow back to the battery and complete the circuit.

We used one of the fused circuits to connect the system to the auxiliary truck power when plugged in for towing. This lead runs up to the trailer pigtail that plugs into the truck, but first passes through a BGA 225 battery guard unit. This unit is designed to disconnect the trailer batteries if the voltage gets to low. It also has a surge suppression function to help prevent vehicle transients from damaging the trailers DC electronics.

Solar electric system

Solar just makes sense these days on an RV if you are going to be off grid at all. Solar equipment keeps getting more efficient and the price is coming down. We have 1200W on our roof and during the summer it almost always provides plenty of power. Even in the winter and cloudy days, while it might not make all the power we need it extends our battery time considerably before we have to run the generator.

Kyle and Olivias Airstream Argosy is a “Minuet” model, which means it is not as wide as a traditional unit. This makes the roof of the RV very curved and made installing solar a bit of a challenge. With some research panels were found that would fit existing spaces on the roof and maximize power output.

It was decided to install four 115W Zamp square panels and two 90W long skinny Zamp panels along side the air conditioner. This will provide a total installed wattage of 640W on the roof.

The Zamp panels had very similar voltage operating characteristics, so when using the mismatched panels, keeping them in parallel was important. Using mismatched panels will almost always degrade your systems output slightly, but a few simple calculations can help you figure out the best configuration to maximize power output.

These Zamp panels came intended to be installed as a kit and included rooftop combiner modules. While we already had a rooftop penetration, we used these units inside and paralleled all the panels together.

After combining the panels we pass all the power through a 60A breaker disconnect and then run down to our electrical cabinet using 6AWG wire. Here we connected the system to a victron 100/50 smart solar MPPT charge controller.

The Victron SmartSolar MPPT is a maximum power point tracking charge controller that varies the voltage across the panels to find the maximum power output. This greatly helps system performance in partial shading conditions.

The charge controller can take whatever solar panel (voltage up to 100V) and convert it to a voltage acceptable by the batteries. The charge controller also manages bulk, absorb and float modes if using lead acid. I really like this charge controller because it has built in Bluetooth and you can check the solar output easily from an Android or iOS device with the app.

After passing through the charge controller the negative lead lands on the negative busbar and the positive lead passes through a 60A ANL fuse before landing on the positive busbar.

Here power will either flow into the battery or combine with additional battery power to flow into the DC distribution or inverter if it is using more than the solar is putting out.

Inverter

The inverter is a critical piece to an off-grid system. The inverter takes the DC power from the batteries and converts it into AC power for the RV which powers the general receptacles, air conditioning and water heater. In this case the inverter is a 120V inverter, but you can get them for european 230V US 240V or even use multple to create split and 3 phase systems.

The Multiplus 12volt 3000VA 120A Charger unit

We used the Victron MultiPlus 12/3000/120 inverter. Two 1/0 cables were connected from the busbar to the inverter, again to get the correct ampacity. While the inverter might only put out 25A AC power, because the voltage is so much lower the amperage could be as high as 250A on the 12V side.

While this inverter converts DC-AC it also can convert AC-DC and act as a powerful battery charger. This inverter serves as the primary battery charger for the system aside from the solar. When connecting to a generator or grid source this inverter will convert the AC to DC and charge the batteries at up to a 120A rate, or around 1500W or power.

We will get back to the inverter in a minute but let’s go over how the AC is connected to the inverter and RV.

120V AC Distribution

This RV is designed as a 30A RV. This means that only one hot and neutral enter the RV and can provide 30A of usable AC power at 120V or around 3600 watts. The power cord for the RV enters directly into the electrical compartment from underneath and immediately enters into our primary transfer switch. The transfer switch is a device that allows power to be passed through the inverter, or directly into the RV, bypassing the inverter.

The big black cord is the RV’s main power cord, it enters through the floor and goes into the gray box which houses the transfer switch

After going through the transfer switch power connects to the AC breaker panel in the PD4000L power center. From here additional electrical circuits were installed using two tandem circuit breakers and one GFCI that powers the kitchen, bath and outdoor receptacles.

The inverter we installed is called a “hybrid inverter” because it can pass power through it and also add power to it. This allows the inverter to limit the amount of power coming in and make up the rest from the batteries. This is huge for an off-grid electrical system in a boat or RV because it allows you to plug into a weak AC source like a 15amp circuit or small generator without overloading it.

A hybrid inverter can add battery power to shore or generator power

The inverter also has one additional function if power is selected to pass through it, and that is UPS or uninterruptible power supply. This basically means that if the shore power is lost the inverter will take over seamlessly and use battery power.

While the inverter is an amazing unit and a critical piece to the system, if it ever failed you would not be able to power the RV’s AC system at all. That is the primary function of the transfer switch, to be able to bypass the inverter if needed. We use ours when plugged in sometimes to give the inverter a rest as well and turn it off.

System Monitoring

With all this fancy electrical equipment pushing power around it would be great to monitor the system as a whole. That is one of the reasons we chose to use Victron equipment all the way around. Victron has a great communication system that most of their equipment can use. Data cables run from the BMV712, the MPPT solar charger and the MultiPlus inverter to a Victron Color Control GX display.

This display shows the whole system and how power is flowing. You can see power into and out of the inverter, power from the solar system and power into or out of the batteries.

This display really helps to understand what the system is doing and keep tabs on how its performing. This screen can also be used to make programming changes to the equipment like changing the current input limit for the inverter to take advantage of its hybrid features.

While we did not set it up the Color Contol GX also has the ability to connect to the internet so you can view the system anywhere in the world if you have a connection.

Outcome

Overall, everyone is very happy with how the system turned out. While the trailer has not yet been to an amazing middle of nowhere boondocking location yet, we put the system to the test with construction equipment during the renovation. We think the battery bank will be able to provide around 5 days of runtime with regular use (not running the AC) and greatly extended if there is sun. Running the generator and combining power from the solar, air conditioning and heat are very possible as well.

We are super excited to see how this system performs once they are using it full time. I also put together a video going over lots of the system details below.

RV Electrical System Walk Thru In An Off Grid Optimized Airstream - Solar, Lithium batteries

Watch this video on YouTube

Here is a list of most of the equipment we used in this system:

Battle Born Batteries – http://battlebornbatteries.com?afmc=1x
Victron Multiplus 12/3000/120 – https://amzn.to/2LRqOAc
Victron 100/50 smart solar MPPT charge controller – https://amzn.to/2LRrAgA
BMV712 Shunt – https://amzn.to/2Su8csp
Victron Color Control GX – https://amzn.to/2RAgyBL
Victron VE Direct cables (2) – https://amzn.to/2VjscQe
ANL Fuse Holder – https://amzn.to/2BUahqx
Battery Disconnect Switch – https://amzn.to/2GSPl9b
250A Busbar – https://amzn.to/2Rwl6IY
Ground Busbar – https://amzn.to/2Sy22rb
Solar Disconnect 60A Breaker – https://amzn.to/2RsUZ5Q
1/0 Battery Cable – https://amzn.to/2SDywAA
Lots of 1/0 Lugs – https://amzn.to/2Vqsmpa
Zamp panels and combiner – https://www.zampsolar.com/
Transfer Switch – https://amzn.to/2VpKGPb
30A breaker – https://amzn.to/2BV1rcc
Box for transfer switch – https://amzn.to/2BUccvf
Progressive Dynamics PD400L – https://amzn.to/2R4aC4k
Wire – 12AWG – https://amzn.to/2R75fl0 (we used a few hundred feet, green,black,whiteand red)

*Disclaimer: This blog post is to share a custom electrical system design and installation for a specific rig and is not intended to be used as a instructional guide to build any other system on any other rig. Working with electrical systems is inherently dangerous and can cause injury to body and property or death. We strongly recommend working with a certified electrician or other professional for this kind of electrical work.

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