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How To Build A DIY Solar Generator

Join the Green Revolution without spending a fortune

Published:
Last updated:
Reviewed by
Robert Laswell
Guide

Across the world, people are taking advantage of solar power, drawn by the falling price of solar panels and a welcome opportunity to reduce their carbon footprint. There are many ways to benefit from the solar revolution, whether buying green energy from sprawling utility solar farms or installing home solar panels.

However, these are not the only ways to benefit from solar energy. Instead, you can use small solar generators that charge batteries and let you power appliances whenever and wherever you need. These portable units are a great solution for powering appliances and tools at home and in the workplace.

A solar generator can provide backup power if the grid goes down, and they are perfect for RV owners or people living off-grid. Unlike conventional generators, you don’t need to buy fuel, and solar generators make no annoying noise.

example solar generator setup diagram

Why build a solar generator?

If you want to buy a solar generator off the shelf, there are many great options. However, they can be very expensive, especially if you want one suitable for high power demands. Fortunately, there is an alternative, because you can simply buy the components and build your own DIY solar generator. You can save a considerable sum of money while building a generator that suits your needs.

While the process isn’t too complicated, if you are unfamiliar with electricity, we recommend consulting an electrician to make sure you build a generator safely.

Navigation

In this article, we will show you:

  • What size generator you need
  • What parts you need
  • Case/box
  • Solar panel
  • Battery
  • Charge controller
  • AC inverter
  • DC meter
  • Battery maintainer
  • Wiring  
  • How to test components  
  • How to build your generator

Stage 1- Work out your DIY solar generator capacity

Before embarking on this project, you should think about what size solar generator you need. For example, if you want to charge a mobile phone while you are camping, you need a much smaller unit than a backup generator that will power energy-intensive home equipment for hours.

Step 1 – Work out your equipment wattage

Before buying any components, add up the wattage of the equipment you will run from the generator at the same time. All of your generator components should be able to handle this total load comfortably.

Step 2 – Calculate the watt-hours

Next, calculate how many hours you run each piece of equipment per day, and multiply this by the wattage to give you the watt-hours (Wh) or kilowatt-hours (kWh). This determines the size of the battery and solar panels you will need for the generator to operate all day.

Step 3 – Component ratings

When you add everything together, you will know the peak output, in watts, and the daily power consumption in watt-hours. For example, a smartphone of 40 watts, charged for three hours, requires 120 watts per hour. A 250-watt refrigerator operating for 24 hours needs 6kWh. A 1000-watt power tool used for an hour needs 1kWh.

Higher wattage components are larger and more expensive, but it is wise to install components that can handle higher wattage than you need. Constantly running equipment at the limits of its capacity can shorten its lifespan, and any extra capacity will support future upgrades.

Step 4 – What about amps and voltage?

Of course, you also have to take amps and battery voltage into account, so visit our solar generator article for more information.

Stage 2 – Gather the components you need

Now that you know the peak output needed, and the total kWh, we can explore what materials you will need.

Step 1- Find a rugged case

The case needs to be large enough to hold all the components, and durable enough to protect the generator from the elements and physical damage. Cases used to transport cameras are perfect, but a sturdy toolbox can do the job just as well as long as it is waterproof and resistant to corrosion.

A smaller box is fine for a camping generator, while you will need something much larger for a home backup generator.

Step 2 – Source some solar panels

Next, of course, are the solar panels, which need sufficient capacity for the task. If you are not sure, you can always add more panels later as long as the other components can handle the higher wattage.

While you can find cheap solar panels, these are often false economy. Your solar panels must handle the elements and last for years. If you want a portable generator, folding panels are generally more useful.

Step 3 – The importance of a good battery

The main benefit of a solar generator is that you can store power for when you need it most. Ideally, you want a battery that balances price, reliability, and portability while giving you the capacity and energy storage you need. This depends upon the wattage of the equipment, and on how long you will be using it.

One option is lead acid batteries, which are cheap and do a decent job of storing power, but are very heavy. While they are more expensive, lithium-ion batteries offer high capacity, quick charging, portability, and low maintenance.

The technology is well tested and they prove more cost effective in the long term. You could also upgrade from 12-volt batteries to 24V or even 48V, although it can be harder to find suitable components.

Step 4 – Look for the crucial charge controller

The charge controller device sits between your solar panels and the battery, and it is crucial for making sure your battery is not overcharged or undercharged. This can reduce efficiency, shorten battery life, and even lead to dangerous overheating.

A good charge controller maintains a constant flow of power to your battery and lets your solar generator work at maximum efficiency. Naturally, if you will be using high wattage equipment, or want to leave room for upgrades, then you need a larger controller.

Step 5 – Find the right solar power inverter

Solar panels produce DC electricity, which is stored in the battery, while your appliances operate on AC power. A solar power inverter converts the DC stored in the battery into AC. An inverter should prevent overloads and have enough capacity to cope with your intended maximum load in watts.

Step 6 – Manage power use with a 12V DC meter

A DC meter lets you know how much electricity the panels are generating and how much power you are drawing from the battery. A good meter with an LED display isn’t expensive and will help you manage power usage.

Step 7 – A battery maintainer can be a good idea

While a battery maintainer isn’t essential, it can be a useful component if you don’t use the generator very often. These clever devices protect your battery from running down when you generator isn’t in use by sending small amounts of energy to keep it fully functional.

Step 8 – Connecting it together with breakers and electrical wiring

You will also need good quality insulated electrical wiring and breakers to connect the components safely. We have a useful guide on selecting wires of the correct size and type. You will also need a power outlet that you will mount to the wall of the case, a master switch, and internal fuses for extra safety.

Stage 3 – Building the solar generator

Now that you have all the components, the next stage is to assemble them into your solar generator, which requires some planning.

Step 1 – Testing the components

The best place to start is testing the components to make sure they are in full working order.

Solar panels, charge controller, and battery maintainer

Fortunately, solar panels, charge controllers, and battery maintainers are easy to test. You can connect them separately to the battery, making sure you attach the wires to the correct positive and negative terminals. If the battery lights up to show it is charging, you are ready to go.

Try out the inverter

You also need to test your inverter and make sure it is ready for operation. Connect the inverter to the battery and to an appliance to check if it works. If all your components are in order, you are ready to start assembling your solar generator.

Step 2 – Some trial and error

Naturally, your first job is involves fitting the components into the case, which can be a bit of a puzzle. This may take some trial and error to make sure everything fits and ensure you can access everything you need easily.

Start with the battery

Take your time and start with the battery, because it is usually the largest component. One useful tip is to attach the battery to the case with battery straps.

Place the outlets

Next, decide where you are going to place the various outlets and master switch for easy access. One useful tip is to place the 12V DC meter on the top of the casing so that it is easy to read when you are using the generator.

Add the other components

With the battery and outlets in place, you can now start laying out the other components in their approximate final position to ensure that nothing is blocked and difficult to access. When planning the layout, make sure that wires and components do not get in each other’s way and that you can reach everything you need.

Drill holes and fix components

Once you are finally sure, you can start drilling holes for the outlets, master switch, inverter control panel, LED display, and other external components. Adding some silicone sealant around the holes to provide extra waterproofing is a useful addition.

If fixing a component in place means you won’t be able to access the terminals, you can always attach it permanently later on, after you have wired everything together.

Step 3 – Connecting the external components

After you have tested the components and placed them in position, the next step involves connecting them all together with wires and fuses. Most components arrive with instructions and wiring diagrams, so make sure you follow these.

Wire it all up

With all components installed in the case, it is time to wire everything together, making sure you add fuses where needed, between the solar panel and charge controller; charge controller and battery; and battery and inverter.

Connect the DC meter

Wire the DC meter to the battery according to instructions, generally connecting one wire at a time and the negative terminal first.

Connect the inverter

Connect your inverter to the battery, according to instructions, and secure in place. Only connect a single wire at a time, to prevent shorting or electrocution, and connect the positive first. You can fix the inverter in place with straps for easy access.

Fix solar charge controller

Before fixing the solar charge controller to the inside of the case, connect it to the battery and then to the solar panels.

Connect the solar panels

You can connect the solar panels with plugs, which let you take the system apart, for portability, or by direct connection to the other components, which is more durable.

For direct wiring, simply run the wires to the charge connector and attach the negative and positive leads. For plugs/connectors, wire according to the instructions and, whatever method you use, be careful not to cross the wires.

Step 4 – Testing and using your solar generator

With your unit complete, you can test it by letting the panels sit in the sun. Keep an eye on the DC meter to monitor how much current the solar panels generate.

With the testing complete, you are now ready to use your solar generator. Simply connect your appliance or tools and you are ready to go.

Conclusion

We hope that this guide has given you an insight into building your own solar generator. While it takes some work and electrical knowledge, you can save money and make a generator that suits your needs and lets you upgrade at any time.

FAQs

How many watts does my generator need to power my house during an outage?

In most countries, your house needs anywhere between 3 and 7kW to operate essential electrical devices such as refrigerators, lighting, and sump pumps.

How much does a solar generator cost?

This depends upon the size and power. You can build a small portable generator for a few hundred dollars, while larger backup generators can cost over one thousand dollars. Whatever size, they are significantly cheaper than the off-the-shelf version.

How long do the batteries last?

For lithium ion batteries, if you only use the generator occasionally, the batteries will last for years. If you use it continuously, you may need to replace the battery pack after a couple of years. There are ways you can extend battery life, by not draining the battery completely.

Although I am competent at DIY, I don’t know much about electrics. Should I build a DIY solar generator?

As we noted above, you should always seek the advice of an electrician if you are not sure. One alternative is a solar generator kit, which costs more but gives you a much easier introduction.

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Author Bio

Robert Laswell

Robert is a renewable energy and sustainability specialist with 10+ years of experience in the solar and renewable energy space.

With experience in different organizations in the industry, he operates semprius as a passion project promoting sustainable renewable energy ideas and products.

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