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Free 900-Watt Solar Plans (For RVs and Schoolies)


How to build a 900 Watt solar system

Download the higher resolution diagram here. (Our Diagrams are always Free!)

In this article we’re building a 900 Watt RV solar system.

Amps per day

Expect up to 385Ah per day in Summer (without DC-DC Charging).


Actual performance varies greatly based on location and weather conditions. Your results may be far better or worse.

Who is this system for?

Fully Off-Grid RV Travelers – Schoolies

How much does it cost?

Without batteries, this system cost about $2,300

Project Overview

A 900 Watt Solar system combined with DC-DC (alternator) charging is a massive system that will create a lot of power. This system size is perfect for RVs, Travel-trailers and Schoolies.

Before we begin, let’s take a look at this solar system’s 3 separate sections. Each section is built independently, in any order you like, just be sure to only connect them at the end of the project.

The Solar Array in this system is built using 5 x 180 Watt solar panels wired in series.

The Component Board is the “power distribution section” of your system. This is mounted to a board to make assembly easy.

The Battery Bank – We recommend a minimum of 600Ah of lithium or 1200Ah of traditional lead-acid batteries.

Here is a list of everything needed to build this project.
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Components Needed

Large Components

Battery Options

We recommend a minimum of 600Ah of LiFePo4 Batteries or 1200Ah of AGM Batteries.

Wiring and Terminals

Double-check wire length and terminal size prior to ordering premade cables.

The Solar Array

The solar array is built using 5 x 180 Watt solar panels wired together in series. This means you’ll connect the positive from one panel to the negative of the next panel, forming one single string of solar panels.

Since they’re wired in series, their voltages add together. In this case more than 124V in cold and sunny conditions. That’s high enough to be considered very dangerous. Make sure to take all necessary safety precautions or hire a professional.

You’ll need 6mm² (10 AWG) Solar Cables to go from the solar array to the solar charge controller. Install a PV Circuit Breaker on this cable in an easy-to-access location.

6mm² (10 AWG) is the smallest cable you should use between charge controller and solar array, but it is always safe to use larger cables. The charge controller in this design can handle cables, up to 35mm² (2 AWG).

The PV Circuit Breaker is used as a disconnect switch in this system, it is not used as circuit protection. Since there is only one series string in this solar array, additional fusing is not necessary.

Mounting the Solar Panels

The safest way to mount solar panels to a vehicle is by bolting them to a roof rack. This gives you peace of mind that they’re not going to fly off compared to gluing them on.

Also, in the future you can change your solar panels layout easier if they’re simply bolted to a rack.

Since this size solar system is most likely going to be installed on an RV or a Schoolie, options for bolt on roof racks are limited.

Here are some roof rack options for ideas.

Another option for mounting solar panels is to use a Panel Mounting Z Bracket Kit. Once these are installed you wont be able to change configurations. But this option is very secure if you use bolts and washers to mount them.

Our least favorite method is using glue-on brackets like these here. Many people use them, we’ve even used them ourselves with no problems. You just have to be aware of the strength of the substrate you glue them on.

ie: If you glue these mounts to a painted vehicle roof and the paint flakes off, the solar panels will fly off!

Many factory vehicle paint jobs are poor in quality, especially on the roof of cargo vans.

The Component Board

For a vehicle-based solar system, I recommend mounting your smaller components to a board. This allows you to comfortably do most of your wiring at home, and when you’re ready you can bring the entire assembly to the vehicle.

Try to mount as many components as you safely can to the board.

This is a rough idea of how your component board might look like. Be sure to pay attention to fuse locations.

Mount your component board securely in the vehicle, somewhere easy-to-access since the majority of your fuses are located here. It must also be located near the Battery Bank and the Power Inverter in order to keep the cables short.

The Solar Charge Controller and DC-DC Charger will generate heat so be sure to provide adequate ventilation.

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The Solar Charge Controller

This design uses a Victron 150|70 MPPT charge controller, meaning it has a maximum array voltage of 150V and will charge your battery bank with a maximum of 70A.

This controller in combination with a 900 Watt solar array will produce about 63A during cold and sunny weather conditions.

It’s important to program your charge controller for the type of battery you decide to use, this is to prevent damaging the batteries. Whether LiFePo4, Gel, AGM, or any other battery type, you can program the charge controller by following the steps in its user manual.

The Battery Bank

For a system this size we recommend installing a very large battery bank. At least 600Ah of Lithium, or 1200Ah of AGM. However the larger the better.

This system will produce a lot of energy in summer, and the DC-DC Charger will add to that every time you’re driving.

You’ll need to buy 12 Volt batteries and they must be wired together in parallel. That means connecting all the + terminals together, and all the – terminals together, forming one large battery bank.

LiFePo4 batteries are what we recommend for vehicle installs. They’re half the weight and twice the usable capacity of traditional lead-acid batteries. Plus they have a much longer lifespan, so in the long run, they end up being cheaper.

Here are a couple of LiFePo4 options that make sense for this size solar system.

Traditional lead acid batteries can be used if you’re on a budget. If you are using lead-acid batteries, search for AGM batteries, they’re a great option with a lifespan of 3 to 6 years

Most popular Battery Monitoring Shunt

Installing a Battery Monitor

Every solar system should have a way to monitor the state of charge of the battery bank. Without this, you run the risk of over-discharging your batteries which will lower their capacity over time.

The easiest way to monitor state of charge is by using a Battery Monitoring Shunt.

This simple device is installed on the negative cable of your battery bank, so that all current must flow through it. This enables it to track how much current goes in and out of your battery bank over time.

Most of these units come with either a physical display which you can mount on a wall. Some however have bluetooth funtionalilty, enabling you to monitor battery health on your phone.

Summary

This 900 Watt Solar System is a great size for an RV or Schoolie. When you pair this system with a large battery bank, for instance 1200Ah of lithium, you’ll have a vehicle that you can comfortably go Off-Grid for several days.

This size system can support a whole family or group of friends, wherever the adventure takes you!


Download the free wiring diagram above to view the system layout with wire sizes included.


Use this list which includes everything you’ll need to build this solar system.

Other Useful Resources

Guide to Wire Size Selection Learn to size your wires the uncomplicated way. Learn more…
Guide to Fuse Size Selection Fuses protect your investment. Learn how to size them quickly and easily. Learn more…
The Basics of Solar Energy The bare minimum knowledge, in less than 10 minutes. Coming Soon…

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