8 Steps to Building a DIY Off-Grid Solar System

Although the prices of solar panels have been falling gradually since 2007, the cost of an off-grid solar system setup is rising steadily. However, any homeowner with a basic toolbox can install it on their own, which can help reduce the overall system cost substantially.

The reason why many decide to hire a professional (or give up on the idea entirely) is the seeming complexity of the process, when in fact, if you pull it to bits you see that individual steps are not at all intricate.

The following article is structured as a step by step process which teaches you how to choose the appropriate batteries, solar panels, inverter and charge controller, and then instructs you on how to connect and set them up properly.

Essential components

In order to build a basic off-grid solar system, you will need the following components:

• Solar panel
• Batteries
• Inverter
• Charge controller

Out of your toolbox, you’ll want to take out a few items like copper wire, breaker, meter, fuses and MC4 connector.

Contents

• Calculate the load
• Select the battery
• Select the solar panel(s)
• Select the charge controller
• Select inverter
• Mount the solar panel
• Connect the components
• Wire the components
• Step-by-step guide to building an off-grid solar system

The next segment provides detailed instructions on setting up an off-grid solar system, with a few important safety notes.

1. Calculate the load

Before selecting the individual components, it is crucial to calculate your energy needs. Don’t let this scare you, as it is just basic math.

• First, make a list of all the appliances that will be run and define the number of hours they will be dependent on the solar energy.
• Second, check the specification chart of each appliance on the list to find out their power rating.
• Next you need to calculate the Watt Hour: WATT HOUR = RUN TIME x PRODUCT POWER RATING

Lastly, calculate the total Watt Hour. It is the number you get when you calculate Watt Hours for individual products and then add them all together.

2. Select the battery

Homeowners typically choose to install solar panels to have backup power in a shorter-term outage, or to empower an off the grid structure.

Now, to be certain that all your appliances which require constant rated voltage are powered at all times, and that you have enough power for the nighttime, you are advised to go for the deep-cycle battery. Unlike car and bike batteries, deep cycle ones are designed to enable partial discharge and deep slow discharge – what this means is that they can charge during the day, and then gradually discharge between no more than 45 and 75% of their capacity.

Before you move on to other components, you should decide between 12/24 V or 48 V system voltage. Those who plan on powering a smaller home typically go for 12 V or 24 V, while 48 V are reserved for high power-demanding structures.

3. Select the solar panel(s)

The purpose of a solar panel is to convert the sunlight it receives into electricity as direct current (DC). They are typically categorized as monocrystalline or polycrystalline, the former ones being slightly costlier, but more efficient.

The solar panel you select should be capable of fully charging a battery you chose in one day. This part can be a bit tricky, since the amount of sunlight highly depends on the geographical area, time of the year, and a number of other factors. Nevertheless, regardless of the location, it is safe to assume the panel will receive sunlight on average for 4 hours.

Common misconception is that solar panels are powered only when the skies are clear, and they receive direct sunlight, when in fact, they are capable on producing electricity in cloudy weather as well. However, they produce around a quarter of the electricity as they do on sunny days, and only 10% on an extremely cloudy day.

4. Select charge controller

Charge controller is a device placed between a battery and a solar panel, used for the regulation of current and voltage that is coming from the solar panels. It regulates the charge to the battery as the input voltage from panels rises. That way, charge controller prevents the battery from overcharging.

There are three types of charge controllers to choose from:

• ON/OFF, known as the least efficient one
• MPPT, maintaining the status of a highly efficient charge controller, but also a costly one
• PWM, which delivers satisfying results at a fairly affordable price

The final decision should be made based on your personal preferences, but our advice would be to go for either MPPT or PWM.

5. Select the inverter

Inverter is a device used to convert the direct current into alternating current (AC), that is, the electricity that powers your appliances.

There are three types of inverters for solar panels to choose from:

• Square Wave, that comes at the lowest price, but is not adequate for all devices
• Modified Sine Wave, which is not suitable for capacitive and electromagnetic devices, such as microwave, fridge and most types of motors
• Pure Sine Wave is adequate for the majority of appliances and is thus more efficient than the Square and Modified Sine Wave

The power of the inverter you choose should be higher, or at least equal to the total number of load you’ve calculated in the first step.

6. Mount the solar panel

It is crucial to set up a solar panel on a ground or rooftop were there will be no obstruction of sunlight. It is also important to tilt it to the right direction – if you are on a northern hemisphere, point them to the south, or point them to the north if you are located somewhere on a southern hemisphere. This way, you ensure they capture maximum sunlight.

One of the methods used to firmly secure the panels is to use concrete that should be poured at each leg of the stand.

To mount the panel to the stand, use inbuilt holes on its sides to screw it to the stand. You will also find a small junction box on the back side of the panel with negative and positive sign of polarity. Junction boxes on smaller panels come with external wires, while on larger panels, they come with terminal wires with MC4 connector. 

Use black wire for negative, and red wire for positive terminal connection.

7. Connect the components

Although you’ve calculated the battery capacity and solar panel rating, note that these sizes are not readily available in a form of a single unit. To make up for the difference, you need to add either a small panel or batteries that would match system requirement.

To match the adequate current rating and voltage, you will need to use series and parallel connections.

• Series connection – Connect the positive terminal of one device (solar panel or battery) to the negative of the other.
• Parallel connection – Connect the positive terminal of one device (solar panel or battery) to the positive one of the other.

8. Wire the components

Our advice is to start with the charge controller and connect it to the battery first in order for it to get calibrated. First connect the negative wire from the battery to the negative terminal of the controller, and then connect the positive one.

If you do it correctly, indicator led lights which indicate battery levels will light up on the controller.

Next, connect the charge controller to the solar panel by connecting the wires that you find in the junction box. At this point you will need an MC4 connector.

Safety notes: When connecting the charge controller with the solar panel, make sure the panel is facing away from the sun and cover it with a dark material. This way you avoid potentially damaging charge controller with a sudden high voltage from the solar panel.

Furthermore, when connecting the two devices, positive terminal on the panel should be connected to the positive terminal on the charge controller. The same goes for the negative terminal. Most people decide to use wires of different colors to avoid the mix-up, that can result in breakage, or even fire.

Final words

We hope the instructions we provided helped you set up your off-grid solar system. Should you have any doubts, feel free to get in touch – we will be more than happy to provide answers and advice on the best devices you can get for the project.