DIY Solar Generator Concepts and Equipment – For Beginners
Kyle
How to Build a DIY Solar Generator
If you are reading this, then I assume you are similar to how I was when I was first looking at home backup solar generators for my home. I was lost in a sea of unfamiliar terminology and concepts being used. From previous experiences I had some basic understanding of electricity and I had some experience with wiring in my home. But there was a lot to learn before I was able to finally select a backup solar generator. After selecting a backup solar generator I became more interested in solar power and I then went on to build a DIY solar installation which I currently run 4 home circuits full time on solar power. These 4 circuits I run full time on solar provide power to my home office, bonus room outlets, mini fridge, most of the upstairs and downstairs lights and smoke detectors. I’m continuing to learn and expand my solar setup.
Whether your a DIYer looking to build your own solar generator setup or looking to purchase a portable solar generator for camping or home backup power, I hope the information below will help you understand some of the most common terms, concepts and equipment used. And best of all, its all in one place!
Update: Since originally posting this, I’ve now built-out a 12v and 24v DIY Solar Generators. Check out these posts:
Be sure to also checkout my YouTube channel for additional information.
Here is a video of the same content as this post.
At the bottom of this post I will list links to the DIY solar equipment I use if you would like to take a look.
Basic Electrical Concepts
When I first started looking up watts, volts and amps the actual definition only confused me more. For example, this is the definition of a volt “The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI)“. What?? Those definitions were meant to be understood by electrical engineers. So below I will attempt to explain my interpretation of these concepts.
Watts – (W) – watts are the actual energy used by an electrical device (such as a light or appliance). Abbreviated with ‘W’ such as a 60W light bulb. A 60W light bulb while turned on is consuming 60 watts. It is common that some appliances actually state the wattage very prominently. Light bulbs and microwave ovens are good examples.
Volts – (V) – A volt is unit of measure for electromotive force. Volts are kind of analogous to water pressure in a water hose. However, volts are abbreviated with a ‘V’ such as 12V, 24V, 48V and 120V.
Amps – (A) – Short for amperes – An amp is the unit of measure for electrical current. Current is the speed or rate at which the electrons flow through a conductor. An amp is analogous to the flow rate of the water in a water hose. Amps are abbreviated with an ‘A’ such as 20A or 40A.
watts (W) = volts (V) * amps (A)
This equation is very important to understand and remember. You will commonly see solar equipment use all three of these terms and you will need to know how they relate to one another.
To better understand, here is an example of how they relate. Lets say you have a 1000W microwave oven. To use the microwave, you would plug the microwave into a standard 120V outlet in a home. Since we know that the microwave is using 1000W and the voltage is 120V, then using the formula (1000 watts = 120 volts * ? amps) we can solve the equation (amps = watts / volts) to figure out how many amps are being used. 1000W / 120V = 8.33A.
DC – Direct Current – This is the type of current produced from solar panels that flows into your charge controller and then stored in your batteries. You use DC current most likely every day. DC is commonly used to charge your mobile phone, electric vehicle, laptops, etc. Typically when you plug your phone’s charging block into a wall outlet to charge your phone, the block is converting AC current into DC current. An inverter can be used to convert DC current from your battery into AC current to power your normal appliances and tools such as a light bulb or microwave. More about inverters later.
AC – Alternating Current – This is the type of current produced by the power grid and transmitted into your home. When you plug something into the standard wall outlet in a home you are using AC current. AC current is used because it is cheaper to produce and has less energy loss when transmitted over long distances. The transformers up on the telephone poles outside on your street convert the higher voltages from your electric company down to safer voltages (120V) for customer homes.
PV – Photovoltaic – PV materials and devices convert sunlight into electrical energy (DC). A solar panel is a PV module device. A solar panel consists of PV cells. You will see the term PV referred to when shopping for solar wires that run from you solar panels to your charge controller. One positive + wire and one negative – wire. The wires run to your solar charge controller which is labeled as PV input (+ and -).
Solar Panels
When shopping for solar panels you will always see them rated in watts. Unless the conditions are perfect, you will most likely not see the panel produce the rated watts. I believe the rated watts were set based on perfect 70 degree and clear sky conditions. On cloudy days, you will probably only see a panel produce roughly 15 – 30 percent of the rated watts. On mostly sunny days the panel will probably produce 85 – 100% of the rated watts.
There are 3 basic types of solar panels – monocrystalline, polycrystalline and thin-film. Here is the basic difference of these types.
Rigid Solar Panel
Monocrystalline solar panels offer the most performance out of the 3 types of panels. They are about 15-23% efficient converting sunlight into energy. They are more expensive than polycrystalline panels.
Polycrystalline solar panels does not perform as well as monocrystalline, but they are more cost effective. Polycrystalline panels are about 15-17% efficient.
Thin film solar panels are the most expensive and offer less performance than monocrystalline panels. However, thin film solar panels are flexible and can be installed in ways rigid panels cannot.
Most solar panels are your typical rigid solar panel installed on roofs or ground arrays. These panels are weatherproof, durable and designed to be outdoors all of the time.
There are also foldable solar panels typically used in portable solar generator applications. These foldable panels are not always rated to be outdoors all of the time in the rain. Some say “splash proof” or they may actually have the IP68 waterproof rating. These foldable panels are designed to take up less space when not being used and easily portable with handles.
Foldable Solar Panel
Solar Panel Array
A solar panel array is simply combining two or more panels together to produce electricity as a single system. The more panels you add to your array the more power you can produce. If you have two 100W solar panels connected, your array can produce up to 200W.
Mobile Ground Solar Panel Array (4 panels)
There are two basic ways to combine your panels. You can combine your panels in series or in parallel. The panels are typically connected together with wires using weather proof MC4 connectors. MC4 connectors typically come with your solar panels. Since this is a beginner article I will not go into detail on how to wire panels together in series or parallel. Here is a good article on deciding on whether to choose series or parallel. and how to do it In summary, when you connect your panels in series, the voltage is cumulative but the amperage stays the same. If you connect your panels in parallel, the amperage is cumulative but the voltage stays the same.
Here is a simple example of wiring together a solar panel array:
Let’s say you have two 100W panels you combine in series and each panel is identical and can produce up to 21 volts and up to 11 amps each. If you combine the two panels in series, then the array can produce up to 200 (100 * 2) watts, 42 (21 * 2) volts and 11 amps. Notice that the amps did not change, but the volts and watts doubled. If you combine the two panels in parallel, then the array can produce up to 200 (100 * 2) watts, 21 volts and 22 (11 * 2) amps. While in parallel, the watts and amps doubled while the volts did not change.
You will need to ensure your solar charge controller can accept whatever voltage and amperage your solar panel array is producing.
Solar Charge Controller
A solar charge controller has a rather simple job in concept. It takes the current produced from your solar panels and uses it to charge your battery. The voltage and current from your solar panels is constantly fluctuating as clouds go over. The charge controller regulates the voltage and current coming from the solar panels going to the battery. Solar chargers come in two basic types.
PWM – Pulse Width Modulation – These charge controllers are less efficient and physically smaller. However they do cost quite a bit less. PWM solar charge controllers are rather limited as far as maximum voltage input. From my experience, PWM controllers typically support only up to about 400W. While MPPT solar charge controllers can go considerably higher.
MPPT – Maximum Power Point Tracking – These are the most advanced and popular solar charge controllers. These controllers are much more efficient, sophisticated, physically larger, greater voltage input but more expensive. They come in a variety of sizes typically in the 20A to 100A range. This refers to the maximum amount of current the charger can charge the battery. In almost all cases, I would recommend getting a MPPT solar charge controller over a PWM. My MPPT charge controller is configurable with a mobile app via Bluetooth connection. It can also charge multiple battery types.
Inverter
An inverter converts DC current from your battery into 110V-120V AC current which is what is used in households for most appliances and tools.
AC is type of current in your standard wall outlets. Inverters are typically rated in watts and are designed for a certain voltage such as 12V, 24V and 48V. When choosing an inverter, the first step is to make sure it matches the voltage of your battery or battery bank (12V, 24V or 48V). Then you can select an inverter with the amount of watts that meets your electrical requirements. You will also need to determine if you need a pure sign wave inverter or a modified sign wave inverter. Modified wave inverters are much cheaper. In most cases unless you are only powering some old drill or something, you will most likely need a pure sign wave inverter. A pure sign wave inverter is suitable for sensitive electrical devices where as the modified sign wave inverter may damage them.
Battery
The battery is the store of energy for your DIY solar generator setup. In almost all cases you will want some battery storage for your solar setup. During night or cloudy days you will need to rely on your battery or the grid for your power needs. I could easily write multiple articles on choosing a battery. So since this is beginners article, I will just focus on the basics.
Here are the top two battery types used in modern solar setups.
Lead Acid – These are the batteries that have been used in solar installations for years. There are many who still prefer lead-acid batteries. These are the cheapest option to get started. However the batteries lifespan is not as long as other battery types and will need to be replaced sooner. They also require more maintenance.
Lithium-Ion – There are two types of lithium batteries used today – lithium nickel manganese cobalt oxide (NMC) and lithium iron phosphate (also known as LiFePO4 batteries). LiFePO4 batteries are all the rage these days. Seems like everyone is moving to lithium iron phosphate. LiFePO4 batteries have a much longer lifespan. They can be fully charged and discharged every day over 3,000 times and still maintain 80% of their charge capacity. Some LiFePO4 batteries are rated over for over 5,000 charge cycles. These batteries could easily last 10 years or more. LiFePO4 batteries are also the safest battery. They don’t catch fire or explode like some other lithium batteries can. The only downside to LiFePO4 batteries is that they are more expensive and are heavier. I recommend LiFePO4 batteries.
12.8v 100ah LiFePO4 Battery
When choosing a battery, you will see that they are rated in volts and amp hours. Most LiFePO4 batteries are offered in 12V, 24V and 48V. You can see in the battery image that it has 12.8 volts listed. This is nominal battery voltage for this battery and very common. When we say 12V battery, that is referring to the voltage class of the battery. In this case 12.8v is that actual nominal battery voltage but is considered a 12V battery. You also see it says 100Ah. This refers to amp hours. You don’t see it on the battery image, but this battery has 1280 watt hours of storage. This is abbreviated as 1280Wh. Let me explain these.
Watt hours (Wh) – watt hours is the measurement of energy storage in batteries. One watt hour is the equivalent of 1 watt of energy consumption for 1 hour. Watt hours are abbreviated as “Wh”. 1280Wh for example. If you had a battery that was capable of storing 100Wh and you had a LED light that consumed 5 watts, then you could power that bulb for 20 hours from that battery (100Wh / 5W = 20 hours). An even simpler example would be that for that same battery, you could run a 1W LED bulb for 100 hours (100Wh / 1W = 100 hours).
Kilowatt Hours (kWh) – a kilowatt hour is 1000 watt hours. Kilowatt hours are abbreviated with “kWh”. For example: 1280wh = 1.28kWh. You will commonly see kWh listed on your electric bill.
Amp Hours (Ah) – amp hours is another way to measure energy storage of a battery. Amp Hours are abbreviated as “Ah”. An amp hour is the amount of energy in a battery that allows for one amp of current to flow for one hour. However, amp hours can be the source of confusion. I wish all batteries has watt hours printed on the side instead of amp hours. Remember from above watts = volts * amps. So when using amp hours as a measurement, you must consider the voltage in order to determine the actual storage potential. So look for the watt hours measurement of a battery when shopping for a battery. A 100Ah 24V battery has twice the storage than a 100Ah 12V battery.
Just like solar panels, batteries can also be combined to form one battery system called a battery bank. Also just like solar panels, batteries can be wired in series or parallel. The concepts are the same. See the picture below for an example of wiring two batteries in parallel. This example is two 12.8V 100Ah batteries wired in parallel resulting in a 12.8V 200Ah 2560Wh battery bank. These two batteries are what powers the 3 circuits I run on solar power every day. It is important that the wires connecting the batteries together are the same gauge and length. The red positive wire in the top left and black negative wire on the bottom eight eventually go to the inverter and solar charge controller not shown.
Two batteries wired in parallel
For more information of wiring batteries in series or parallel, check out this site for more information.
Some DIY solar generator setups don’t have a battery at all. Those battery-less solar setups require a special type of solar charge controller which has an internal battery and can provide unvarying consistent power directly to your inverter.
Solar Generators (AKA Solar Power Stations)
A portable solar generator contains all the 3 components (solar charge controller, inverter and battery) all in one nice package. They are also called portable power stations. They have all the built in protections that protect itself and that makes it safe to use. But all those features come at a price. You will most certainly pay more for a portal solar generator than building a DIY Solar Generator. There are many companies selling these power stations such as Jackery, Bluetti, Ecoflow and many more.
Common Features include:
Standard 120V AC outlets for powering your appliances and tools – Some even have 30A RV style outlet
Multiple 12V USB outputs including USB-A, USB-A fast charge, USB-C 100w and cigarette lighter style plug.
Wireless phone charging
Multiple ways to charge the generator including solar and AC
Pass through charging which just means they can be used while charging
Most can also be charged with solar and AC at the same time which results if very fast charging.
They typically have small displays providing good information on the state of input and output and battery percentage
Some have built-in Bluetooth which can be used to configure and monitor the generator from a mobile app.
Solar generators are typically shown in watts and Wh (watt hours). The watts of course referring to the built-in inverter continuous output capability and the watt hours referring to battery storage capacity. The built-in inverter also has maximum watts surge rating as well which is typically double the watts of continuous output. I don’t remember ever seeing one of these solar generators that did not have a pure sign wave inverter.
The one in the image below is my solar generator. It is a Bluetti (pronounced Blue Etty) AC200 Max. It has a 2200 watt inverter and 2048Wh of battery storage. I also added on the B230 expansion battery doubling the battery storage. It is a very nice solar generator and I am happy with it.
Solar Generator – 2200w built-in inverter
I have both the Bluetti AC200 Max and a DIY solar generator. My manual transfer switch allows me to run off of normal grid power or easily switch to solar power for up to 10 circuits. I will post another article about that. Improvements will be made to DIY Solar Generator over time. I plan to eventually make it to a 48V DIY Solar Generator with a 6500W inverter and 10,000Wh battery storage (10kWh).
I hope you have enjoyed this article. Please checkout my other blogs and YouTube channel for more information. I plan to put out many more articles and videos on DIY solar power and other interesting subject.
I cover a variety of preparedness and self sufficiency topics such as DIY Solar Generators, Living Off Grid, Generators, Vegetable Gardening and growing your own food, Water and Food Storage, Water Catchment, Emergency Lighting, Product Reviews and other topics I’m interested in.
