My intent with this article is to demystify solar energy for the average prepper off-grid type of scenario. Solar installers have created a mythology that solar is somehow hard to understand, and that it is inherently dangerous. Neither of things are true. But they can be true if your approach is one solely of casual infotainment.
Right off the bat I am going to tell you to not even consider doing a whole house solar system, government subsidies or not. You don’t want to be advertising that you have electricity when most people don’t. And depending on where you live, whole house solar is a dead-end anyway.
If you don’t require air conditioning, solar can look promising at first. But a chain is only as strong as its weakest link, and in a solar system, that weak link is the power inverter between the DC batteries of the system and your AC home appliances. The details of this are outside the scope of this article. So suffice it to say that if you are considering a whole home solar system, do your homework and speak to people who have tried to live with one in your area. The Elon Musk panels run at about 8% efficiency, just an example. So do your homework.
My approach is stay small and modular. Solar is a wealth of free and fairly reliable energy for a lot of useful things in a forced off-grid situation, but I think you should stick to mostly DC. Your home security system already runs on 12v or 24v DC already. It usually has some kind of wall wart to power it, and the cameras either have their own 12v connection, or they are powered over the ethernet by the central unit.
Your internet connection also uses wall warts, as does your internet and cable box generally. If you have satellite internet, that also will be generally 12v. And with a 12v/19v converter of the correct wattage, your laptop, computer, and monitors can be easily adapted to run off of the batteries you will be charging with your solar.
Do not plan to run devices “live” off your your panels, directly. You can do that sometimes, depending on how many panels you have and how bright the sun is shining, but it really isn’t good for your devices if the amperage suddenly crashes when a cloud passes. Plan to use a battery. But I am getting slightly ahead of myself.
Solar Panels
If you think of your system in terms of a “generator,” solar panels can provide you with essentially unlimited fuel. Eventually solar panels degrade, and eventually they fail. But that takes a long time, many many years.
In my first run at solar, back in the early days of Prepping 101, I reviewed a small solar system from Harbor Freight. It was a joke back then, and they still sell it. There were not a lot of affordable options back then. But these days solar panels are available everywhere, and they are crazy cheap.
Back then all solar panels were rigid, and made of glass. That has also changed. There are still glass, aluminum framed solar panels. And they still make them in both monocrystaline and polycrystaline, with the former being more efficient for the size. But for preppers, I highly recommend plastic, semi-rigid panels, as I showed in the video. They are cheap and work perfectly. And compared to the panels I first bought back in the day, you get a lot more power out of a smaller package, without the fear that you are going to drop them and smash the glass.
There are also now many versions of solar panels that are attached to cloth, to make something of a solar blanket. Folded back over itself a couple times, you end up with a really good amount of power for a not a lot of money.
Figure just under $1 per rated watt for the flexible panels, and just over $1 per watt for the ones that are mounted on cloth. And that usually includes a charge controller, which I will get to.
Voltage, Watts and Amps
When you get into looking at solar, it can be a mess to understand if you don’t have a background in electricity. Solar panels will be advertised at 12v, 18v, 24v, 30v, 48v, 60v and so on. If they have a rating tag, usually it will say things like max voltage, max amps, max watts. That is because the actual performance of these panels is subject to not only available light, but also manufacturing tolerances and degradation. You are buying a range of performance, not exact performance.
I will do a followup article in this series on what panels actually produce, but for now let’s focus on what they are supposed to produce.
If you back up and look at the rated output voltage of a panel, it will be somewhere above the voltage of a standard lead acid or lithium storage battery, which are all around 12-15 volts. Or it will be some multiple of that. So an 18v panel will be to charge a 12v’ish system, and a 30v panel will be for a 24v’ish system, and so on.
Panels can also be daisy chained to increase the voltage of the output. This can be valuable if you are covering long distances with your wiring. A higher output voltage means you can use thinner wires for a comparable distance. But voltage gets more dangerous and prone to arcing as it rises, so beware that you have to be very careful with this stuff and how you wire it.
Panels have a positive and a negative lead. Usually there are two cables attached to the panel, and they will usually have what is called an MC4 connector. But watch the video for an all in one system that uses another common option.
When you combine two or more panels, they can either be connected with positive to positive, which is called in parallel, or positive to negative, which is in series. In parallel, the voltage does not increase as you add panels. Ten 100 watt panels with an output of 17.4 max volts each, connected all positive to positive and negative to negative, will still be at that voltage range. You add the watts (or the amps really which I’ll get to) for the max performance of the system, which is never even close to the rated capacity.
In series, the amps, of the system does not increase, but the voltage ads to each other, and the watts will also total. So two of those same panels will feed a max 34.8v, but they will still output the same amps, but because you doubled the volts, the watts will double. If you strung ten of them together, the system would be running at max 174 volts. But likewise, it would still measure at the same 6-7 amps, unchanged.
Watts is a simple multiplication of voltage times amps. Voltage measures how had the current pushes. Amps measures how much current is flowing through the system. Watts is what I call “voltage neutral” for an apples to apples comparison of how much power is coming through. Increasing the voltage of your system can be done by running panels in parallel, but decreasing can only be done with a transformer, except for one specific case, which I’ll explain.
You may want a higher voltage for an inverter, especially a whole house inverter. Solar installers demanded long ago that grid tie inverters eat higher voltages so they could use thinner wires, which are much easier to deal with because they are more flexible and less prone to breakage. If you plan to use an inverter, you will need to match the voltage of your battery bank with what the inverter is looking for as the ideal voltage. A higher voltage will blow components. A voltage too low will usually hurt performance.
Batteries
For solar you don’t usually use car type batteries, or even “deep cycle” batteries made for RVs and boats. Sealed gel-cell lead-acid batteries are much more practical, and they have taken over the industry almost entirely. As I explained in the video, I stick to lead-acid get cells for fixed locations. If you are building a ham radio backpack, like I did for Prepping 101 many years ago, a lithium battery is much lighter, but I have not had good experiences with them long term.
The last thing you want is to go to use your solar system in a grid down situation, only to find that your $700 LifePO4 battery will not hold a charge.
Wiring your batteries is much like the solar panels. If you run all of the positives to the positive and all of the negatives to the negatives, in parallel, the voltage of your system will stay at the same. For lead acid that is usually around 13.8v. If you wire them positive to negative, the same voltage increase occurs that I explained with the panels.
In a large system with a lot of batteries, you can wire some of them in parallel, and those run a couple of those strings in series. So if you had say 10 batteries, five would be in parallel per “side,” then the two sides would be wired positive to negative. On one side of the ten batteries you would take off the positive, and on the other side the negative, running the system at 27.6 volts’ish.
Generally you want to run your panel voltage in the same range as your battery bank. So if you get 48v panels, you will want to run your batteries in series to reach that voltage range. Likewise if you decide you want to buy an inverter that is looking for 48v, you woud want to to daisy chain 12v’ish solar panels together and connect them to a similar battery bank, using a charge controller.
This does not prevent you from taking 12v, or 13.8v off of the battery bank. Each battery is still the rated voltage, so you just connect your 12v appliances and electronics to the two terminals of one battery.
Obviously it would be best to include proper fusing in these supply lines. There are now easy diode based fuses that you can inline within the panel chain, but for your devices you really should get a 12v fused terminal block, and connect that to your battery.
Just be careful. Electricity is not something to be escared of, but it can of course kill you if you get sloppy.
Charge Controllers
The middle component is the charge controller. Yep. It is just as simple as it sounds. A charge controller is meant to shut the panels off when the battery is fully charged, and it will also shut off the output if the batteries sink below a voltage that will damage them.
Charge controllers are cheap, like under $10 for a 30 amp simple model. They are all rated by amps, which can be a little confusing, because solar panels are usually sold by watts. This is only because most controllers can handle at least a couple ranges of battery banks voltage and solar panel output voltages. Generally you will see them say that they can handle 12v-24v, or 12v-48v, or in the more expensive ones, into the hundreds of volts.
You do have to do the math on your panels to see how many amps they expect to generate.
Throughput is what a charge controller is all about. So as long as the internal components can handle a given voltage without degrading, volume is volume.
If you dig into the details of a charge controller, it will say something like “If your battery is 12v, the max panel input is 25v. If your battery is 24v, the max solar panel input is 50v. ” The amp rating will determine how many watts they can handle, but it does double with voltage. So a 30 amp controller will be able to handle about 360 watts at 12’ish volts, and 720 watts at 24’ish volts.
Most charge controllers will recognize your battery type, and whether you are running your system at more than 12v’ish, but many are also meant for lead-acid only. And as you can see in the video, a lot of “all in one” packages that come with panels and a controller will be just for 12v’ish systems.
A charge controller will have a positive and negative terminal for input from the panels, a positive and negative terminal for the battery or battery bank, and a positive and negative for load.
Most controllers cannot handle input from other than solar panels, like a 12v wall wart. And a solar controller cannot be used for wind turbine generators. They need a “dump load” connection that is not required by panels. The controller can safely turn the panels off and on without needing to divert current. The panels just heat up instead of charging the batteries.
Most inverter instructions will say to hook your inverter directly to the batteries, not to the load output on the inverter. This is because the lugs on the charge controller are small, and not meant for big fat wires that most inverters require.
A Modular Approach
I decided to go back into this subject for a solid overview because of a really frustrating conversation I had with a “prepper” friend of mine. He has a “bugout” place on the west coast of Florida. I brought up the subject of solar with him and he insisted that “I can’t get solar over there.” I was dumbfounded. But this was the same guy who insisted that food storage consisted of a $700 trip to Costco for organic almond flour and a few bags of rice.
He said that he had contacted solar installers and they told him that they don’t service that town. Apparently the small electric company has issues with tying your solar to their grid, so none of the area installers of whole home solar will touch it.
From that I ascertained that what he was really saying was “I can’t get a government subsidy for solar there.” So that was the end of that conversation.
My suggestion is that you keep your solar plans small and modular. I only explained battery banks and panels in series so you wouldn’t be afraid of it. Personally I think a large battery bank is just asking for trouble, and, like buying 50,000 calories of organic food at Costco, it is a false sense of security.
If you run an oil burner normally for heat, the igniter converts a 120v input current into about 10,000v. Generally it consumes less than 6 amps, so under 750 watts. So to convert that from your battery bank, if you have say 4 panels at 100watts each, which will at most put out about 6 amps, each one will power your oil burning being on for one hour per hour of full sun. In the winter grey skies you may be under 3 amps/hr., or even less.
A 100 amp/hour battery will store up about 5 amps of energy before the charge controller shuts it off as it is drained and not replenished. There will also be inefficiency between the batteries and the inverter, so figure maybe a total of 4amp/hrs for actual use. This is an example where you will want a larger battery bank that could be really useful. One sunny week could take you for many cold nights when the skies go back to grey.
But I would not hook that same system to your well pump, or your irrigation pump, or even your lights or ham radio, or your internet and computers. For lights I would use ones like I recently covered, and for the well pump and irrigation pump I would get 12v or 24v pumps.
If you are on an artesian system with a pump at the bottom of your well, you may have to go to a higher voltage option, but stick to DC, and make sure you test it in advance. Your head is probably not very deep, unless you are on a mountain, so figure out what you need before going out looking. Ebay and AliExpress have a lot of them. You just have to find them. Then tie right into the well side of your pressure tank. You can get a pressure switch at Home Depot or Tractor Supply, or also on the above sources. I am going to cover this at some point, but if I could figure it out myself, so can you.
Likewise for irrigation pumps. There are very inexpensive pumps that will give you several gallons per minute.
For electronics, they range from 24v down to 5v, and the charge controller will probably have a couple of USB ports right on it for charging phones and tablets. For 12v things as I said, you can get a fused terminal block. And for higher than 12v there are cheap converters for common computer and monitor voltages all over the place. Just figure out what you need, and build that, in pieces. So if one goes down, you have a backup, and if one blows up, it doesn’t take everything else down.
This is NOT a Hurricane Folks
Whenever there is a quasi-natural disaster, like the recent manufactured storm on the west coast of Florida, a lot of people start thinking about keeping these kinds of resources on hand. If you do not intend to live “off-grid” for now, spending resources on this stuff just doesn’t come to mind. But we are not talking about building a resource for a couple of weeks, or even a couple of months. if you focus on small and affordable, for key tasks, it could be that you can retain a resource that could last for years. Just don’t get caught up in thinking big, and allowing that to paralyze you. The American taxpayer is not going to subsidize your one panel, a charge controller, and a 12ah battery for your ham radio. You’ll have to pay for that yourself. But there is also not a lot to regret if you never need it. And lets hope you never do.
Resources:
Dokio semi-rigid solar panels – on Ebay from <$1/watt
Dokio cloth systems – also on Ebay
100ah battery – on Ebay $169
MC4 multi-connectors – on Ebay
Inline MC4 Fuze – on Ebay
Fuzed 12v terminal blocks – on Ebay
(this is by no means an inclusive list but it gives you an idea of how easy it is to get this stuff)
It seems obvious to me that you dont actually understand how this works. You know just enough to be dangerous. You should really educate yourself about the difference between a pwm charge controller and a mppt charge controller. You seem to have a basic misunderstanding about different voltages and how the charge controllers work. I appreciate that you are trying to help people but you just kept getting into the weeds about random things that dont matter. There are several youtubers that could help you. An excellent video about the charge controllers is by “cheap rv living”….also Will Prowse is very educated. You dont have to have a system at or near 12 volts to charge 12 volt batteries….that is what a charge controller is for……and most can work on a 24 volt system too.
For small modular systems it really doesn’t matter what type of charge controller you use, which is why most come with a PWM controller. People like you are the problem. And it is why I spend time on explaining things to people so that morons don’t scare them away explaining how they won’t understand it unless they follow these guys. Charge controllers are meant to work in a range, even though the range can be pushed. And they are primarily to protect the battery from overcharging. My information comes from people who make these things, not youtubers.
The charge controllers do matter and you are doing everybody a disservice by not spending 15 minutes to educate yourself so that you could educate others. I am not the problem….ignorant people pretending to be a source of knowledge such as yourself are the real problem. This isnt rocket science but you have a general misunderstanding of what charge controllers do. Ohms law is a thing brother.
If you bothered to actually read and watch you would see that I explain Ohms law, and how it applies. I didn’t need to explain MPPT vs. PWM because the panels that I suggest come with the charge controller, and they are generally PWM. I specifically tell people to stay away from installations that would benefit from an MPPT controller, because they are a waste of resources. It was a virtual guarantee that a solar installer would show up to this article to ‘splain that I got it all wrong. I don’t overcomplicate things because it paralyzes people into inaction. You are most likely an infotainment guy anyway, and have no interest in anything outside of your little conformable box. I hope reality does not squash your little box flat.
i am interestd