This article is not for the faint of heart. Like many of the overview articles in this Prepping 101 series, the topic of solar systems is fairly simple, but you have to learn the basics to get started. With what is here you should be able to take action and get going while avoiding a huge learning curve and the pitfalls that such a complicated learning curve can entail. In our first article on solar we looked at a very simple do it yourself kit from Harbor Freight. For more than a few light bulbs, that kit is lacking the energy to do much of anything, and it doesn’t even come with a power inverter or battery. The other side of solar is the big money option. Houses are being outfitted with solar every day all over the country. With enough panels and controllers and batteries, you can run your whole house on solar for a totally off grid lifestyle. For preppers, this is not a viable plan. Part of what we are doing has to be kept a secret, because when the system breaks down, we don’t want people to know that we have food, water, radio, and even working lights. We are so outnumbered by the sleeping masses that there will be a huge dichotomy between those that have and those that don’t. A solar array attached to your roof will not only tip off your neighbors that you have stuff they don’t, it also makes you a target for any overflying aircraft who have been ordered to take out survivors “hoarding” resources.
The survival approach to solar is to build a system that will meet your needs for basic conveniences, but that also can be moved in an out of the house. I wouldn’t even put panels out for the first month of a disaster. It is just too risky.
There are two options for that. One is buy a complete “solar generator” system from a company like Earthtech Products that we linked to in the first article. I ordered this kit and added a third panel to it, to be tested in a later article. Per watt this is going to be your most expensive route, but the one that is probably least likely to fail you. It separates out the charge controller from the discharge circuit, allowing you a much higher draw with a lot of circuit protection. The problem is, you can’t expand the Earthtech system beyond a certain point, so it would have to be used modularly within the specifications supplied. As you’ll see if you read below, the actual power that you need for different applications is a little more complex than you would imagine.
The other option, and the one we are going to cover this time, is to piece together a solar system from online suppliers. It will consist of essentially the same things we found in the Harbor Freight kit, panels, charge controller, voltage inverter and batteries. For most piece together systems you will also need to buy or make connectors for all of the parts. This article came about because, as is very common on the first try, I bought some wrong stuff. I’ll explain as we go.
To start, be very careful about buying any solar gear without looking hard at the numbers. One person will advertise a system as 3,000 watts, while another seller will advertise the same product as 10,000 watts. In both cases the sellers are referring to the same inverter capacity, and one is quoting the working load while the other is capitalizing on the peak load rating. Neither of them explain how much solar power you can collect and store in the system, or how long it would take to collect it. The 3,000 watts is usually just the inverter capacity, or how much you can theoretically use at one time, subject to other limitations within the system. We are going to go over the numbers below, and don’t get lazy with this. Solar is a sea of misinformation and ongoing technology development.
There are basically two types of panels, monocrystalline and polycrystalline. I won’t bore you with the differences in how they are made. The takeaway is that monocrystalline are more efficient, so they are generally smaller for the same wattage. This is a moving target however, because pollycrystalline technology is still evolving, while monocrystalline is pretty much done. Because my panels are going to be moved in and outside, I elected to go with the smaller and less floppy monocrystalline. They also work better in higher ambient temperature, and this system is going to be used in Florida.
Panels are rated by how many watts they produce, or could produce under ideal sun at peak efficiency. Your actual results may vary, but the number is handy to compare panel to panel. The “watt” is a measure of power that is voltage neutral, because the amount of power at the 12-18 volts produced by the panel, converted to 120 volt household current, will have roughly the same watts (minus some losses in the converter). If a panel says 100 watts, that equals about 8 amps at 12 volts (8 x 12 = 96), or a little under 1 amp at 120 volts (100 amps/120 volts). Your flatscreen TV probably runs at about 200 watts, so it draws a little less than 2 amps at 120 volts. You won’t be running your TV directly from the panels, which produce DC current and not the AC that most household things run on, but that should give you a basic understanding of what you are buying in terms of power.
I am going to refer to several Ebay deals in this article, but in no way am I suggesting that you buy anything from any of these sellers. To understand the difference in mono vs. poly pricing, I found this guy who has a calculating function on his panels. You can choose mono or poly, flexible or non-flexible, and see the wattages available. Right now poly panels are running at about $1.50 a watt and mono are around $2 per watt. You can of course find exceptions. I did not buy my test panels from this guy and he doesn’t even carry the option I chose, which was to buy hard 40 watt mono panels, 5 of them, for 200 potential watts per hour. It was part of the kit that I purchased, seen here in the pictures (don’t buy this kit!). Remember this number 200 watt number as we go through the other variables.
One thing I should note is that you see I bought this kit directly from Hong Kong. His add right now has a $200 shipping cost, but many of the sellers from China include free shipping. Don’t worry about getting ripped off ordering directly from these sellers. With tens of thousands of ads every day on Ebay and millions of happy customers, there is no danger to buying these panels shipped directly from China. I have bought dozens of things directly from China, including all of this solar stuff. The guys selling in the US are just getting them from China and marking them up. If those Chinese fools are still willing to take by all rights worthless Federal Reserve banknotes in exchange for actual products, let them have the numbers on the screen. When the crash comes their dollars will be worth nothing and our panels will be making free energy.
Once you understand the concepts below, feel free to buy a package deal like I did, just don’t buy that one because the inverter is not in US current as I’ll explain below. The package deals can save you some money, but read well.
Because most of you know what a power inverter is, I’ll start with the charge controller. To review, the charge controller acts as an intermediary between your panels, your batteries, and your outgoing load (usually to a power inverter). It makes sure that the batteries are not overcharged, nor will they be allowed to reach an undercharge status that will hurt their lifespan. The charge controller is not usually expensive in the type of systems we are talking about here, and they even come with some panels. To buy the standard 30 amp controller that everyone is using is usually in the $30 range on Ebay. If you calculate 30 amps at 12 volts, that equals 360 watts. I have seen the 30 amp controller sold with up to 600 watts of panels though, because the panels never reach even close to top efficiency.
More importantly, the outgoing amps are of concern if you intend to power AC appliances with an inverter. A regular refrigerator runs at about 10 amps, at 120 volts AC. That is about 1200 watts. If the outgoing power from your batteries is being throttled at 360 from the charge controller, you won’t be able to run your fridge no matter how many battery banks you have connected or how highly your inverter is rated. When the draw exceeds 30 amps, 360 watts, it shuts off.
This is a very important key factor that you absolutely have to understand. If you connect your inverter directly to the batteries with no charge controller, you could potentially draw them all the way down and cut their life span to next to zero. If you bypass the controller, you have to either get an inverter with its own battery protection (shown below), or manually calculate the power you have stored, the power you are using, and shut the system down manually at 50% used. If you want to test this as you go, unhook the inverter and hook the charge controller back up. It will tell you the current available voltage. Don’t go below 10 volts ever.
There are charge controllers that can handle 80 amps, but even then, running the fridge just isn’t going to happen. That is the biggest difference between a conventional gas powered generator and a solar setup. The solar has limitations that just aren’t present in a gas genny, but the genny runs out of gas, and a solar setup doesn’t run out of sun. Most components with solar have years of guarantee. The panels have like 25 years. If you are going to spend money on a powerful gas genny or a long lasting solar system, for a hurricane or blizzard the gas genny is of more practical use, but in long term survival, mostly for the conveniences of life, you’ll get a lot more mileage out of a solar setup. Just understand that it is expensive to get serious capacity. Whole home solar systems can be built to run high draw applications, but again, this has to be kept on the down low, and it has to be somewhat moveable.
The most common battery for solar power storage is a 100 amp/hour lead acid deep cycle battery. They can be purchased on Ebay for just over $200 each, shipped. In a race to capture customers, these batteries are now being created with higher than 100 amp/hour capacities, but per amp/hour they seem to be the same in overall cost.
For the math, a 100 amp/hour battery is 100 amps at 12 volts, per hour. That is 1200 watts/hours, so theoretically, if you want to deplete the battery not under 50% of charge, you can draw 600 watts for an hour from this battery, or 300 watts for 2 hours, or one 60 watt lightbulb for 10 hours, or five 15 watt LED light bulbs for 10 hours. This is why I tell people to take small solar with a grain of salt as to how much it can really accomplish, especially in those long grey winters of New England and many other parts of the country. On a grey day your panels are only going to be running about about 20% efficiency. There will be super sunny days that you might be able to do a load of laundry or cook with your induction burner, but there will also be weeks on end that you will be lucky to keep the lights on at night.
Most people will daisy chain several batteries together for more capacity in those times when the sun isn’t shining. You do this by connecting them in parallel, all the positive terminals connect to each other and all the negatives connect to each other. This will keep the whole system at a 12 volt output and simply multiply the amp hours stored in the system. Theoretically you can connect as many batteries as you want in this fashion, but I haven’t tried more than 4 at a time.
This is the opposite of connecting the batteries in series, which means positive to negative. When you connect in series, you add the voltages and halve the amp/hours. Therefore, if you want to run a system at 24 volts, 36 volts, 48 volts, etc., you would connect 2, 3, 4 batteries in series. Then, to extend the amp hours at that voltage, you would connect those arrays in parallel. It sounds complicated but it isn’t. Neg to neg and pos to pos you add the amp hours and the voltage stays the same. Neg to pos you add the voltages and cut the amp/hour rating in half.
I went out on something of a limb for this article series and spent a good deal on money on Lithium Ion batteries to test as an alternative to lead acid. After considerable research I discovered that LiFePO4 Li-Ion batteries are the best solution for long term power storage with a constant charge and drain cycle. They are made for abusive high draw conditions and hold top voltage for longer in their discharge cycle, up to 80% draw. This is really important for things like radios and expensive power inverters that balance the entire circuit on a constant voltage. If you wish to read a Powerpoint presentation on the differences between LiFePO4 and other types of Li-Ion, the BatterySpace.com website, where I bought mine, has a very good overview here.
I bought four 100 amp/hour LiFePO4 batteries at a cost of over $600 each from BatterySpace. As a comparison, for $2400 I could have bought a dozen lead acid batteries, so I don’t know if it was wise or not. My feeling is that until you try them, you don’t know. But I do know that people who take this seriously spend the money on the Li-Ion, so take it for what is worth. As you can see on the BatterySpace page, they make LiFePO4 packs that are up to 200 amp/hours, and they do it the same way I described above, with 3.2 volt arrays. Each cell is 3.2 volts, so 4 of them in one pack, connected neg to pos, is 12.8 volts in series. You can then daisy chain them in series for higher voltage and less amp hours, or in parallel for more amp hours at 12.8 volts. These batteries are created for high draw applications, so Battery Space developed their own load balancing 100 amp circuit board that can be hooked to their cells. I just spoke to the tech department there and was told that you only need this under high draw conditions. If you plan to run less than 30 amps in discharge, he said that a regular charge controller should work. Their PCM board is a high end optimization to give the battery perfect even charging of the cells so they last longer. Think electric cars. That’s what it is for. Their 100 amp high end charge controller is individually wired to each 3.2 volt cell, and he said you can run those in parallel and just buy one PCM, but it isn’t plug and play by any means.
This LifePO4 was a rabbit hole I maybe shouldn’t have gone down, so you have to do some of your own research if you plan to go this route as well. I personally have had a lot of lead acid batteries go south on me over the years before their rated time that I thought the Li-Ion battery was safer long term. I am probably right, but there is a lot to learn. You should note that the life cycle of these batteries is listed as 1000 cycles (80% of initial capacity @ 0.2C rate), which means that they will go three years being quickly recharged and drawn down 80% every day for three years. On low drain survival stuff, how long? Indefinitely?? That was my thinking.
By now most of us have had some interaction with a power inverter of some type. Walmart will sell you a basic 12 volt to 120 volt adapter that plugs into the cigarette lighter of your car and that can run your laptop. Inverters for solar are not really that much more than that, except that they are generally bought for higher capacity, and they are made of better materials in a better design. I can’t explain to you what the sine wave characteristics all mean, but there is clearly an entirely different class of inverter for running a serious system. And they aren’t cheap.
Inverters are generally sold by watts. The larger inverters you will find at auto parts stores and even Costco generally don’t go past 600 watts, and they may or may not have the sine wave properties of the really heavy duty devices. From solar suppliers, and on Ebay, you’ll find inverters that stretch up to 15,000 watts, with peak power numbers to 60,000 watts. There are levels of technology that apply to these devices, so don’t rush into buying anything. I made a bad mistake when I bought my first solar kit on Ebay because I didn’t notice that the inverter had an output of 240 volts at 50 hertz. That is European voltage. In the US, our stuff runs on 120 volts at 60 hertz, and though you can step down the voltage, you can’t change the cycle rate. 50 hertz will damage most motors that are set up for 60 hertz, so that inverter is nearly useless here.
Recently I found this seller on Ebay that has what seem to be the most advanced inverters of today. If you read through the ad, he shows you all of the terminals and connections, and in broken English explains that the inverter also contains a battery backup function, and that you can use it to charge your batteries from wall socket AC, similar to the EarthTech generator mentioned above. If you buy one of the high power ones, that means you can you leave your refrigerator connected to it and plug it into both the wall and your solar powered battery array. It will automatically fail over to your batteries when the power goes out. Then when the power comes back on it automatically switches back. It also will make sure that your batteries are charged from the wall current even if the solar hasn’t filled them yet.
This battery backup function is probably why his inverters can handle such high peak loads. As he explains in the ad, most appliances, especially those with heater coils and motors, require a giant spike of wattage to get going. Some motors even have a special capacitor on the side that they use to help the motor get turning, and that is essentially what the internal battery is on these inverters. They can punch through a burst of wattage without damaging the toroid transformer inside. Cool stuff. They also have a battery low light, which is helpful if you are using high drain appliances and you haven’t had any good sun for a few days. As explained above, you won’t be able to use a regular charge controller for things like the refrigerator or your well pump, but you could use this inverter. If you want to spend the big bucks, in excess of $1,500, and get up into the huge wattages, you’ll need to run your system at 48 volts. I don’t intend to run anything big so I stayed at 12 volts in, and that limited me to an 8,000 watt inverter. My guess is that the larger units require so much throughput that the cabling would be too big to be manageable, the subject of which we will get to next.
If you can only afford an inverter that is $500, please compare all of your options at that price to this guy I have linked to who is advertising 2014 technology. As you can see from his ad, he shows you the improvements that have been made just in the last year, and in the years before. I included the swimsuit hottie picture here to show you what to stay away from. Read the specs on the other sellers who are selling that visibly look like the same inverters. They have much lower power ratings. The swimsuits are meant to hide the fact that I think they are liquidating old stocks of old technology.
My humble suggestion, and one that I plan to follow myself, is to depend on solar power as little as possible, and at 120 volts even less than that. Several smaller high quality inverters are going to be better than one big one, because if the transformer fails in one, you could always steal one away from another task to go run the radio for an hour or whatever. These high end inverters use toroid transformers, which are in a donut shape. They are much more reliable and resilient that a traditional transformer, but they still do fail. The mosfet controller chips are even more prone to failure, and if you read the docs on the unit, they are only rated for several years of use. Notice in this guy’s ad that the important parts are not made in China. It is weird that a Chinese guy would be say that they get their mosfets from Germany so that they are high quality. I linked to this guy and purchased from him because he seems to be at the front of the pack. But at the end of the day, your inverter is the biggest failure point of a solar system, period.
And again, note that with big powerful inverters like the one I just bought, you can’t run your charge controller between the inverter and your batteries. There has to be a direct connection because most charge controllers can’t handle this much outgoing wattage. Be careful with running too much draw on the whole system. This is not a technology that has been tested under fire. Their primary customer is the construction industry, not preppers, though we are catching up.
Connections and Wiring
The good news about wiring is that you don’t have to re-invent the wheel. My “kit” didn’t come with any wiring so initially I did my own research as to what gauge wire I needed to run my system, then I went and bought it at Home Depot. but when I opened up the back of my panels I realized that there was a standard connector for which they are made. It is called an MC4 connector, and they are weatherproof. Most people seem to run negative and positive as male and female on their systems. This is what I am doing because I can just buy pre-made cables and cut them in half to connect to the charge controller. I also got lucky that they sell a 5 way parallel connector, as I happen to have 5 panels, so I was able to get two of these connectors and 10 short cables, plus one long cable to to back and forth from inside to the connectors and I’m all set for the panel to inverter connection. You can also buy the wire in rolls and the connectors separate, but you need to also get the right cabling tool for MC4. It is all available on Ebay of course.
What surprised me most is that the wire gauge used in most of the cabling seems to be one or two sizes bigger than you need. I don’t know if it is just because the cables tend to be out in the sun so you don’t want them to get any hotter than they need to be, or if one person at the beginning just decided to go a size up and it just stayed that way. If you do the math, even a 160 watt panel is only putting out 13 amps of current, and if you look at the wire rating chart, you wouldn’t need 12 gauge wiring unless you were going 50 feet with it. Yet most of the solar is 10 gauge. So if you do plan to make your own connections, be aware that the standard may be a little fatter than you would think from regular ratings charts.
The cabling between batteries is still a complete mystery to me so I’m still going to do what everyone else does. It appears that most people use 2 gauge wire with heavy connectors between the batteries, even though according to the chart, you can run 40 amps 3 feet using 16 gauge wire. That’s like 500 watts, which is a lot of juice to begin with. Even if you were going to say maybe 6 gauge, just to be safe, but 2? I don’t know. It is definitely a topic for more research. There seems to be a lot of crossover between welding cable and golf cart cable and solar cable. Size 6 wire in less than one foot increments between the paralleled or series connected batteries should be fine.
What Can You Run?
Now that you are starting to understand the components in a modest solar setup, you should be able to do basic math as to what kinds of things you can run using what equipment you can afford. I was in an electronics and appliance store today and walked around turning things over to see how many watts they take to run. A 46″ flatscreen is only about 250 watts. A slow cooker is only 250 watts. But an electric burner that you can use to fry with is 1,000 watts or more. Even induction burners run to 1,500. A can opener is surprisingly 1,000 watts and a washing machine is 500 to 700 watts. Your home refrigerator is probably about 10 amps, or 1200 watts, and your cable box and home computer are usually not more than 200 watts.
As you can see, a basic solar system with several batteries could bring a lot of comfort to a mandatory off the grid life. Being able to watch movies, use the washing machine, even being able to run a vacuum cleaner once in a while will bring a lot of convenience to life. Basic cooking can be done with solar periodically if you can store the power, and every sunny day that goes by is yet more free power that you might as well use. Solar power is pricey and not for the light of heart or the mentally lazy, but if you got this far in the article, you aren’t mentally lazy and you probably have done your homework to see that some sort of collapse is extremely probable. Let’s hope it never happens and we just use our solar when we can’t get campsites that have electric hookups for our RVs. That’s as off the grid as I ever want to be, but I am prepared if the need should arise. Once you understand the way the numbers work with solar, the hardware is just a matter of budget, but I hope you at least don’t make the mistakes that I made. Anyone want to buy a 50 hertz inverter? They won’t let me send it back to China.