This picture was chosen to highlight that you have to really pay attention to the numbers when buying solar. There are tricks like this meant to get you into ads that advertise an old generation of technology for the same price as the new generation. Deep in this long article you will find all of the details to make your choices right the first time.
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.
This is the “other” system that we bought and that hasn’t been set up yet. It is a complete “solar generator” from EarthTech. There are advantages to this approach but you will pay roughly twice the cost per watt.
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.
This is the basic kit that I bought for this article initially. It consists of 4 small moncrystalline panels, a charge controller, and ooops, an inverter made for European current.
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.
Panels
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.
I linked to this add on Ebay because it highlights the cost differences in the panel types. The flex panels were not yet available when I bought mine.
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.
Charge Controllers
This is the charge controller that comes with a lot of systems and that sells for about $30 separately. It can handle 30 amps, or 360 watts. Look at the bottom for how the connectors work.
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.
Batteries
This is the battery that came with my EarthTech system. I upgraded that system to 4 of them, which is the maximum it can handle.
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.
If you plan to piece a system together, this brand is all over Ebay in multiples, and even higher than 100 amp hours.
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.
Please see the article for my story on these high end $600 Lithium-Ion batteries. They are probably the best choice, but they require a learning curve.
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.
Power Inverters
I have linked to this inverter in the article, and please read that whole page. There are a bunch of them that look the same, but these are the most recent technology.
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.
These inverters have a battery backup function that allows power to go both ways through the transformer. If you plug it into the wall socket while you have power it will also charge your batteries and act as a charge controller, just like the charge controller from your panels, which would not be used with this inverter.
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.
We all have to live within budgets and limitations, so please see this chart that comes from this inverter ad. Other charts from other sellers don’t have these ratings, so be careful.
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.
He even explains how the technology has evolved with side by side pictures. If you can find a better and more thorough explanation of this, please share it. This is the best I was able to find.
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
These are the MC4 connectors that most people use with solar. They are a weatherproof connector.
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.
For wiring, most everyone seems to be using 10 guage.
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?
This is a chart of nominal wire sizes that you need for 12 volt current over given distances. Between batteries in your system it would seem that 6 guage is even overkill, but to buy connectors premade they are usually either 2 or 4 gauge, so who knows.
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.
What can you connect to a 3,000 watt inverter? Well, a lot of stuff. Check the back of your appliance for the wattage, or the amps, and multiply the amps times 120 to get the watts.
Many good points in the article, many more in the comments. Some more from me: Many appliances that we want to run are are available in 12 volt configuration. The author mentioned radio and TV, for example. Most, if not all, Radios for the home that plug into 120 volt wall recepticles step the voltage down to 12 or 9 volts inside through a transformer and diodes. Please do NOT waste energy by stepping up the voltage through an inverter to 120 just to step it down again inside the radio. Remember the transistor radios from the 50’s – 70′ that used D cells or 9 volt batteries? Find them at yards sales or Goodwill and then add a plug to accept 12 volt input. Or simply go for a modest car stereo. TV’s are also available at 12 volt for truckers and RV’s. But then in a true Grid Down scenario there won’t be very many broadcasters. Also consider CB radios at 12 volts, but I’m not sure I would be comfortable broadcasting thereby revealing my position, depends on the type of catastrophe.
12 volt lighting in LED is now readily available, just not cheap enough yet. Consider building some of your own. The “threshold” voltage for most “white” LED’s is around 3.2 volts. Put 3 of them and a resistor in series and you have a 12 volt light. I don’t remember the value of the resistor at the moment, but I do remember putting several single LED’s into my dashboard using a 470 ohm resistor inline with them. OK, here is a link to LED calculator: http://led.linear1.org/led.wiz
Wiring for batteries: I have personally been involved in 2 Electric Vehicle (EV) conversions. After they have been in service it was found that it is ALWAYS the end of the chain of batteries where “things” get hot, like battery terminals, copper wire ends(lugs). It dosen’t matter if wired in parallel or series, the ends, both positive and negative, carry the most watts/ heat. I solved a friend’s golf cart terminal melting problem by adding several pieces of copper pipe, cut, flattened and drilled, to the terminals as cooling fins. Yes just pointing into the air. That is why you choose the heaviest gage wire, heat dissipation. On a similar note, I have taken apart many used/failed laptop battery packs to retrieve the Li ion batteries (18650- a metric designation). Upon testing the individual cells it was found that it was always the cells on the ends of the chain that failed, ALWAYS. In this configuration – series- the voltage and amps have been added up and meet the last cells internal resistance to create heat therefore failure.
Batteries: I have built a battery “Desulfator” [warning danger using high voltage] for standard and deep cycle Lead Acid batteries. I have had moderate success, 38 %, in reviving dead batteries. These revived batteries are therefore ALMOST free to me, counting time of finding them, cleaning, adding DISTILLED water, plus electricity. The best candidates seem to be the ones that died from sitting too long. I’ll let you research this on your own. Again warning HIGH voltages involved.
The threshold for DC electricity and electric shock through the skin has been reported to be 48 volts, but this assumes dry (not sweaty) skin and low humidity. So yes car batteries can kill you. Wear rubber gloves, face shield (not just safety glasses), real shoes/boots, and don’t stand in puddles.
Whatever those women at the top are selling, i will take
All this info is fantastic but way over my head! My particular curiosity is if the SHTF scenario does happen and the power company isn’t going to be selling electricity in the foreseeable future, and assuming you don’t have to bug out from the house; how can I use my solar system on my roof to provide electricity to the house during the day? I realize I can only charge the stuff I have around the house and no I don’t have or plan to have a battery storage system, but the availability of electricity during the sunshine hours solves a heck of a lot of problems. My system is designed to shut down and “isolate”when the grid loses power. If we could modify our solar systems in these kind of situations for survival, it sure would make life a great deal more bearable. I know I can’t do this in a short term power loss but if anybody can tell me where to get the instructions on how to do it “just in case” that would really be helpful. Thanks.
I am impressed by the commenters to this article and need to study them all. But two issues I hope someone can address are whether AGM batteries a better way to go than Lithium Ion? I know cheaper is a factor, but if I would put in $2000 into batteries would that choice be better served with Lithium for prepper with stay-at-home concept and with mobile applications? My second concept is with mono panels. I need suggestions to what to buy for a nominal 300 to 500 watt solar panal array. I am thinking that many small ones is better than a couple of large ones.
Having been a technical missionary to a third world country in which I installed and maintained solar system and inveter only systems, I would like to add a few thoughts. 1) Separate the refrigerator from the system. There are several companies that make solar refrigerators. Have solar dedicated to the refrigerator only. 2) Build your own battery cables. You can buy the crimp tool to put the lugs on the cable and buy the cable by the foot and save 25-50%. 3) The better the charge controller and inverter, the fewer problems you will have. If your going to trust your survival to a $30 charge controller, at least buy 3 or 4 back ups.
If an in-line fuse is added to protect the wire size in case of a fault, the fuse determines the wire size provided it is located at the battery output. Cables between batteries should still be capable of carrying the maximum current but as shorter wires are used, conductor size is reduced as well due to point that, they become a fuse link should maximum current be required. ie: a 3000 watt invertor should have a 100Amp in-line fuse (at the battery). This type of in-line fuse is obtained from Electrical Supply Companies.
ATTENTION!!
One thing everyone is missing!
Battery wire size is determined by Maximum Battery Amperage Output. If two batteries (equal in ratings) are connected in parallel, the current output doubles, so the wire size has to be increased to handle twice the current. The Invertor out put rating DOES NOT determine the wire/cable size from the battery. If you want to avoid a possible mishap, do not count on never having a direct short to the batteries being used.
Good point. But also note that batteries can be stacked and the current restricted to whatever limit you design into the system. Add a current limiter, for example.
One very good reason to increase the voltage to either 24v or 48v is that a system using higher voltage uses less current for the same wattage drained. Since cables have internal resistance, there is inherent current loss. For example, if you are attempting to draw 480W (chosen for convenience), a 12v system will have to push out 40 amps; a 24v system will have to push out 20 amps; a 48 volt system will have to push 10 amps. Theoretically they all seem similar, but in the real world, the problem arises in the cables feeding the system among other losses…
A copper cable feeding the battery system will have an internal resistance, which increases with temperature. On a hot day, let’s assume a 0.02 ohm resistance for the sake of argument…
THE 12 VOLT SYSTEM EXAMPLE:
———————————————
In order to produce 480W, the 12v system will have to feel a load resistance of 0.3 ohm:
0.3 ohm * 40 A = 12 V;
40 A * 12 V = 480 W.
If the cable produces 0.02 ohm resistance (as earlier assumed), we must add this to the 0.3 ohm load and we have 0.32 ohms, which will drop the available current down to 37.5 amps, instead of the 40. The result is a reduced wattage at the load of;
37.5 A * 12 V = 450 W, or a loss of 6.25%.
———————————————
THE 48 VOLT SYSTEM EXAMPLE:
———————————————
In order to produce 480W, the 48v system will have to feel a load resistance of 4.8 ohms:
4.8 ohms * 10 A = 48V;
10 A * 48 V = 480 W.
If the cable produces 0.02 ohm resistance (same as before), we add this to the 4.8 ohm load and we have 4.82 ohms, which will drop the available current down to 9.96 amps, instead of 10. The result is a reduced wattage at the load of;
9.96 A * 48 V = 478 W, or a loss of 0.50%.
As can be seen, the higher voltage system is much more efficient. Likely, there are more losses in the whole system than just cables. Every component and electrical joint adds some resistance. Therefore, the higher voltage system may be superior in many cases, depending upon the set-up.
Overall, this article is a pretty good attempt to get people started with solar systems, but I would like to add a few notes.
You need to think of these systems as two distinct parts, the solar charging (power in) part and the inverter (power out) part.
I will start with the inverter (power out) part. This wiring will be very heavy through the batteries to the inverter (this includes the wires connecting the batteries to each other). This is a high amperage/low voltage circuit going through the batteries. The thickness (gauge) of your wires are determined by the length of the wires (short as possible!), the voltage of your circuit, and the maximum rated inverter draw (in amps). Typically a 1/0 or so wire gauge (conductor diameter of your little finger) is common, but this size varies for your system. This thickness needs to be thick through the entire circuit FEEDING your inverter. Once inverted to 120VAC, the output line is much smaller, depending on the draw (in amps) and distance of what you are trying to power. This 120VAC part would be the same as if you were using an extension cord from a regular wall outlet in your house. The more/larger batteries you have, the longer the system will operate under load.
Note: Parallel circuits (+ to + and – to -) add the amperage of the batteries and keep the native 12 volts. Series (+ to – to + to -) will add the voltage but not add the amperage. For example, if you have 2-12VDC batteries and 120 amps; parallel= 12VDC at 240 amps. Series = 24VDC at 120 amps. It’s all the same watts, just different advantages to each. One common example would be: typical flashlights are series, using 2 batteries to make 3VDC. I use SERIES for solar whenever possible. I don’t need high amperage to start a diesel engine and higher voltage carries better. Remember, per watt; higher voltage = lower circuit amps=smaller copper=less money in copper per watt= same all the same wattage. I use a 24VDC input inverter and can use a smaller input circuit wire than the same output inverter with a 12VDC input. Remember, this wire size has to go through your battery circuit as well. Remember to place a fuse block in this system! This is a lot of power (heat) to lose control of.
Now the solar charge (power in) section. In general, an MPPT controller is the better unit. That will control the recharging of your inverter battery system. Again, the parallel/series wiring needs to be considered here as well. If you parallel your panels, you have to transmit higher amperage to your controller, which means higher cost thick copper cable, and more loss at a distance. In my application, I use solar to run my travel trailer. I like to park in the shade (think cooling/camo) and run my panels out into the sun somewhere. I have 6 panels and run them in groups of 3 in series to run the voltage up to 65VDC, at roughly 7 amps for each of the 2 runs. I have 2 plugs on my MPPT input for a 65VDC 14amp parallel/series combined input. At 65VDC I can place the panels out farther and not lose much. I have 2 dark green 16ga. 80′ extension cords I use for this. They handle 65V/7amps easily. Why didn’t I just run 130VDC on one serial line? That would be nice, but we’re talking voltage here, and 130VDC is dangerous. It is a safety choice. 60VDC is about the maximum considered safe.
I would like to add, since this is a portable setup, I have colored Anderson type connectors throughout my system to make setup pretty much idiot proof. If necessary, anyone in my family could set it up if I am down or out. Once set up, all they have
to do is plug the trailer in, just like at home. This system will keep the trailer batteries charged, give them the microwave, coffee, recharge tool batteries, run a DVD, Etc. It’s not enough to run the air conditioner, but we don’t have to run the Honda i2000 either.
One other thing I’d like to add is “Buyer Beware!).
Many, if not most inverters, panels, controllers purchased on eBay or other marketplace suppliers have no factory warranty or defective products have to be sent back to China (costly expense) for warranty work. If the price is right, take a chance. If you think you are only going to save a couple of bucks, don’t do it. These things fail and not having a factory warranty can bite you right through your wallet. These sites generally do not tell you there is no factory warranty unless you specifically ask them — so ASK THEM, and keep their reply in case you need to file a complaint with your credit card company, eBay, Amazon, or other. These 3rd party suppliers can be tempting, just realize there is substantial risk.
First, let me say great layman’s article. I have a camp which is totally solar, partially with Harbor Freight panels, and some higher end stuff. Instead of using 120v AC, I opted to use energy efficient 12v DC for everything except appliances.I use a full size propane stove with oven, a old fashioned percolator, found a 19″ tv which like your laptop has a dc adapter, however the tv was 12v, so I wired direct. My refrigerator is a unit from a RV, I run it on 12v DC and propane also. The furnace is also RV, 12v forced air on propane. By not using all 120v AC, I can run my small 600 watt air conditioner every night to be cool. My water heater is an instant on unit on propane, and it ignites with 2 “D” cell batteries. Water pressure is from 12v pump, and provides household pressure. All the comforts of home! The reason solar will never pay for it self is the conversion to 120v AC. My camp is wired just like your home, light switches, standard 120v light fixtures with 12v bulbs, and even the wall receptacles are 12v DC. Only the A/C unit is hard wired for 120v AC. I have 20 Gel batteries, over 100 ah each, which are 10 year cell tower batteries. I have had no failures in 5 years, and use the place almost every week, and often for weeks at a time. The trick is to think how much loss from converting voltages, and to go simple…which sometimes is just more efficient.
Outstanding job in writing and, by the commenters, in adding content to the topic of solar. I will be studying all of them soon. But here are my topics. (1) Better to keep a 12v DC system or turn it into 24v / 48v system? (2) what recommendations do you have for 12v DC appliances? (3) What is a good rule of thumb to determining the desired output for two people off the grid? I am using Excel to try to figure that out and am using 5 kwh output and therefore thinking a 20 kwh input would keep it at a discharge not to exceed 25% on a nominal day. But that number is arbitrary, I really do not know the desired input and output numbers. (4) I am afraid of an explosion with Hydrogen gas therefore would a sealed solar battery array be best? I think lots of people like golf cart batteries, but I think that be due to their price point. From a different point, safety, would they not get a poor choice? Safety is number one concern, adequacy is numher two, and price is number three. I have the desire to keep the job more or less covert therefore do not care about selling power to the electric company. I like the idea of having portable panels and not fixed to the roof. No sense in advertising capabilities to anyone driving by the house. (5) I have lots to learn so I ask for lots of feedback. I am not good at this and need to do my homework thoroughly. After cost, I am okay with spending perhaps $30,000. I have lots of trades people I can hire to do the work but would want to hire a consultant to supervise the complete job.
That is a local solar expert job I think. This article was meant for people who don’t intend to draw a lot from it, so that we can buy enough for simple conveniences like powering a radio, being able to watch movies on the flatscreen, and most importantly, run a well pump. A consistent 5k draw requires load balancing and some real advice.
If you’ve got the tech knowledge a cheaper route to go is to use a UPS ( uninterruptable power supply ) instead of an inverter. I get mine free from the local dump. Over 80% that are left there just have bad batteries and are left in the battery recycling area. My two pride and joys are a Harris 4000 and an APC 2500. These both have true sine wave inverters and front screen displays. They are designed to provide back up power for computers. Yes they will charge the batteries when plugged into a 120 V source and a charge controller can be used in parallel with or without a 120 V source. My Harris has been up and running for 14 years ( audible alarm disabled as it’s always in alarm ) powering my bug out trailer, no 120 V supply, just 180 W of solar and an AirX 400 W wind turbine. Used batteries from a demo job of the Bellevue City Hall 12V 68 AH 2X in parallel @ 48 V. Nothing like showing up @ 0-dark-30 in the morning and making coffee without a generator when you’re 30 miles from power. The APC is used for home backup power, it has 12V 68AH 2X in parallel @ 24 V. It’s grid charged only at this time. It feeds my entertainment system, two lamps, and an APC 250 that runs my pellet stove. I disabled the alarm on the 2500 so it makes no sound when running in backup, but when the 2500 runs out of battery the 250 kicks in and goes into alarm which gives me time to either start the generator or do an orderly shutdown of the pellet stove. I paid $500 for the solar panels and $400 for the AirX wind turbine, everything else was free.
A word (or more) about EMP please.
While I am a EE, I do not claim to know all about the subject. I have collected research that is available to all on the web and it seems to be evident that a single EMP will not cause all the electronic destruction that some predict. For catastrophic destruction multiple EMP’s would have to be timed at the same instance. Russia did conduct such an experiment but with some what undesirable results. Their complete report will probably never be available for others to read (especially their considered foes), but it did not cause the havoc they had expected.
What will surely be damaged is long run wires and cables (TV cable, Phone with exception of fiber, and Power Lines). The power grid is most susceptible to an EMP. Substations will suffer most damage to their transformers and large surge suppressors. Will this feed back to the point of melting wires? Yes, to some degree but not to the point that we will live in the stone age again. While your small electronics will most likely not be damaged, without power over the countryside, they will be of little use until power is restored (on a limited bases). Our power grids are taxed to the max limits even today. To be cautious is one thing, but remember, people in this country are not quitters (well some are) and we can overcome if there is a way.
Lowell
Where to start? Well, ONE: Listen to the guy who designs and installs them! You are not running a FWD that will be sitting upside down and will lose it’s current when the battery acid runs out – GET SOLAR BATTERIES – you need to understand that one metal ‘eats’ the other to make power. Think plates, if the acid is in glass or not are still going to get eaten up. I ran a cabin and a camp for some of my research off my old Series IIa Land Rover and a wind generator. I stayed at 12VDC because that’s what car and trailer parts run on.
Get THIS through your head, if the SHTF you’ll be lucky to be alive, and here is the order in which you will learn you want stuff – this list from 3+ years of doing some bio research: 1) HOT RUNNING WATER – you would trad ANYTHING for hot running water. 2) indoor flush toilets. On a 20*F blizzard night or morning, it’s nice to flush a toilet – and not have to carry the communal ‘honey bucket’ out to the outhouse in ice or storm, And the LAST think you will find you want is electric lights. All that other stuff is just nice toys. Web? what web? EMP has taken it out, remember? Radio? Remember EMP has taken those off line as well, unless you have your (12VDC) receiver (see last installment). A car radio will work fine. It will also run a CD but movies get old (ask anyone who spent even part of the 1960’s on a Destroyer – or at a Forward Firebase ). Just think of your 50th time through your favorite movie in 2 years. For light? OK, I used old non-pressure mantle Aldan (Brand name) Kerosene lamp and mirrors to study and read and use my microscope with. When in camps (at the cabin) I’d use a mix of old tail lights plugged into the vehicle when I could get it down to the cabin – mid-late spring through mid-autum; and a mix of wind and kerosene lamps to get me though my graduate degrees.
BIG CABLES on ANY run. Because of what everyone has said – they flow power (think ‘water’) easier than small cables (pipes).
DO NOT COMPARE OR CONFUSE YOUR LIFE ‘THEN’ WITH YOUR LIFE ‘NOW’. It will be in no way comparable. If you think that they will be, or can be, you are just plain to rich for your own good or you are a fool. Remember that a lot of that ‘cool’ stuff you will want will be fried by an EMP if that’s your scenario. After a few days at my cabin, or on the Western/Eastern slope of the Sierra-Cascade system I could spot a flashlight at 5 miles, the glow of a TV at 10 – yep, a flash light is on-off-on-off – but the blue-flicker of a TV screen is longer and more ‘not right’ than what looks like a flash-light, it tells me one person or a few more are moving around – not beaded down for the night.
Ask ANY vet from ‘Nam and they’ll tell you what’s important to have, and I’ll bet its the same in any war zone – HOT RUNNING WATER. Until you get that figured out, no amount of TV is going to work. THEN you want clean clothes. I sill have an old up-graded to 5 horse power wringer washer my Grandmother used until the mid 1950’s. Not for WTSHTF, but if we ever have our power go out for more than 3 weeks like it did in the mid 1990’s and before that in the mid 1980’s. Came in handy to put hot water though that puppy and get SOME clean clothes going.
You can save yourself one HELL of a lot of money if you sit down with an solar electric engineer and have them ‘spec you out’ a system for what you think you’ll need. Be honest with them about what you are up to – portable solar you can haul up to a ‘mountain’ cabin – and make sure you are on the same page. LISTEN to what he says. Do you know that right now – as I type – there are photo-voltaic cells that are several % more efficient that they ones last year – AND are flexible enough to sew onto tents and back-packs? Probably not, but your Electrical Engineer does. At least have them go over your system and suggest improvements. “don’t sleep with your battery” is nothing I read in the article, perhaps because it’s too basic, like “gravity is ‘down'” but your lungs will thank you, and so might your family if you are in an air-tight assembly, and you happen to catch a bad break, and a battery explodes, or you cause it to explode. Not ALL my calls as a Corpsman was to a battle wound, I saw plenty of other thing too – from blisters on feet (talk about taking you out of action real fast) to the motor poll where every week one or more battery would explode because someone trained in their care and feeding ‘forgot’ because it was just going to be ‘for a second’ or “Just wanted to see” – and his face and hands and eyes were filled with crap and acid and crap and acid and even more crap and more acid.
So – when you get a REAL list of what you want to use – remember EMPs take out nearly all your electronics, and what may not be gone will be taken off the air. So, get read – portable for a FREEZER to store your meat in during the summer? 1) what meat? all the big game is gone. 2) see number 1. Best take a class in preserving ground squirrels and blue jays – and you might even think of learning a breeding program. MAYBE you might want light to keep you chickens laying? You DO know how do do that, right? And why washing your eggs is a bad idea, right? (Think: Europe they are not sold in the ‘refer’ section of the store – how come we HAVE to do it in America? — there is a VERY good reason.) –
I’d pay an electrical SOLAR engineer the $100 they might charge to go over your schematics and ask you some common sense questions, and give your their unofficial nod of approval (I’m sure an official approval would cost more for them to actually DO the calculations on paper and not in their head or follow ‘rules of thumbs’ you wouldn’t learn until grad school) — that $100 is CHEAP insurance to keep you from ending up with $400 worth of batteries and $300 worth of panels that won’t work because you forgot to do X or Y or Z. OR 4 years from now you need $800 to get the right batteries for your system.
An ex-roommate bought 4 batteries from our power company in the 1970’s early 1980’s – he got them for $200 each (a LOT of money back then). They were just under 23 Inches wide, about as tall, and 6 feet long. They were to power his house in the Bay Area in the event of an earthquake since I was about done with my study and had to move to a different area so he got the newer wind generator that backed up our old 1930’s Jackobs, – I just called him up to see if I was telling you the you the truth – and yes, about 35 years later they still hold 80% of their rated capacity. How much is that? Well let’s say with enough inverters around his house, he can function at near 100% capacity for a week. Lose his refer, washer, dryer, TV, cell phones, and his shop (metal and wood), keep his cell and computer (tablets with libraries on them) on and they’d have on-site hot water and lights for nearly ever and ever.
The batteries were taken out of research stations where winter snow/avalanche could take the site ‘off grid’ for up to a month plus (with two graduate student ‘slaves’ manning them) in a ‘catastrophic failure’ (wind and diesel failed to come on-line) and at about 3.5 TONS EACH – they take between .25 and 3 hours of work a month to maintain them. They come up on surplus markets every now and then – what he was NOT ready to do was move them – That was my neighbors job (who had the closest phone about 8 miles away from our cabin) to tell me that he’d gotten them and needed them moved RIGHT NOW – so our long bed wood trailer and a capstan PTO winch with some bock and tackle got them outside the gate by their Midnight dead line – or he’d have lost them – just out side the gate. BUT they were cheap for what they were – routine maintenance rotate out of service batteries, no history warranted, let alone implied in ANY way-shape-or-form. But a helpful hint from an power company worker simply pointed out the wear and tear on the batteries (none) and said “let that be your guide”. Showed us how to unscrew the HUGE caps and check the plates for ‘wear and tear’). And he was gone – he was getting, for all practical purposes batteries which had set in place for about 15 years, never really been used, were well maintained with periodic power ‘dumps’ to keep them fresh – and they are now, 50 years after manufacture, still at 80% of capacity.
That’s like owning a Olympic sized pool – your problem is how to fill it before it settles and get’s ‘floated’ out of the ground. You don’t need to fill it by next week, or next month, but the sooner the better if you don’t want it to ‘rise’ out of the ground. Too fast and it ruins the battery, too slow and it loses power as fast as you pump it in. A couple of fiends loaded him their Wind-generators and control boxes, and along with our’s he had it at full charge in just over a few weeks. I asked him and he couldn’t remember “About a month I think with 3 generators, then I had to finish up, so I rented an industrial charger that used nearly no Diesel, and ran that on a slow trickle charge from 7 AM to 6 PM for a two days I think that topped off the first charge – and that’s a LOT of power”. That sounds right to me as well.
So, while the weak point may look for all practical purpose to be the Panels, I would humbly disagree and say that IMHO the weak point is the batteries. BUT – check with a Photo-Voltaic Electrical Engineer (who does this 8 hours a day like it was his job) and have him either (from low cost to most expensive)
1) sketch you out a system that’ll do what you have negotiated it to do (you WILL downsize when you see what all is involved)
2) CHECK your per-sketched system – bring photo copies of all name and rating plates (and if not possible, names and every number written down on your devices) – you may need to trade in one part for a part that’s $15 more and will not fail inside of 2 years while it carries a 12 month warranty – he’s paid to know what stands up and what doesn’t, what the reputation of brand X is when measured against brand Y – and maybe Brand Y is better for YOUR application that the top-rated brand X. HE’S Paid to know this stuff. You aren’t.
3) have him OK your system after a good long talk (expect about an hour for this talk), or
4) have him DESIGN you a system – more $$$$ yes, but A) it will do what you decided it would do. HE is up to date on what’s there, and may say – can we put this on hold for 4-6 months? X is going to come to market with a Y that put everything on the market today behind by 10 years. AND B) he MAY be able to get you discounts on the parts you are going to need to purchase if you hit it off on the right foot. Knowing what you are talking about and what he’s talking about cuts bills substantially if he’s not having to educate you.
It might SOUND like a lot – and as the Author has said, over and over again: this is NOT rocket science, BUT if you have EVER jumped a car and put that positive cable on the positive pole and gotten a fire-works supply, you NEED help. I’ve worked with numbers a lot before I retired. I’ve PROVEN the ‘random error’ concept several times in my life: 2+3=6. Everyone knows that two times three is six. Right? Right! So simple a 1st or 2d grader could do it? Right? Right!!!
Only when I tossed my math across my office to my office mate to ‘just double check me’ – did he find the problem in the first line of the equation. I didn’t have to pay him, but he just saved the folks I worked for a few thousand dollars – and I MIGHT have caught it had I looked back at my work a week or two later, but as often is the case with long-term projects 5% of the work took the first 90% of the time, so 95% of the work had to take 10% of the time. JUST EXACTLY when I did NOT have time to ‘double check’ myself – it was easier to toss it across my office to my office mate and say – does this look OK to you and his nearly immediate ‘no.’ Set me back in my place quit well. To my defense: HE was a brilliant mathematician, any other defense is simply not defensible. I’d have turned in a brilliant (if I do say so) proposal for an experiment that I was told was going to be funded no matter what — so no one else would have looked at the numbers buried in the grant – and even then, the mistake was SO
THAT is why it’s called ‘random error’ I didn’t fail math 55+ years ago. It’s also why you want a professional (I was a professional too remember, but I wasn’t checking my own work) — to check your work – and if you are serious about using battery stored energy, DO check on surplus batteries – and you might find them from your local power company, from the USFS, BLM, EPA, — military surplus (though they are prohibited from selling you something that works – I once bought a 1 KW (it was listed as, turned out to be a 100 KW) that was auto-start-on-fail (entire camp hooked to generator, turn on a light switch and the Diesel generator the size of a medium pickup kicked on) it was brand new – but it couldn’t be sold working – it needed an oil-pan plug. It was government to government (military to public school) sale, but they have the same for the public as well. It cost the U about $200 to buy and about that much to transport once I’d looked at it and called asking for a pick-up. It ran an entire 2 week long ‘boot camp’ we put ALL our grads doing field work through – just to make sure no would needed to die needlessly in the field.
SO – there are deals out there – don’t jump ship until you KNOW your life-raft will work, be ready to ‘learn as you go’ – and remember you can upgrade batteries FAR easier than you can what powers them. But to start off – DO talk to a specialized electrical engineer or a ‘passive solar’ architect – and get a second set of eyes on your plans – you want to KNOW that you have NOT run a random error into reality so early on, you never go back that far to ‘double check’ your system. To paraphrase Abe Lincoln: If you’ve make a mistake once, you are more likely to make that mistake again, than if you’d never made it in the first place. — Sparking battery leads? ……. Anyone?………Anyone?……….. Buler?……… Buler?…… Anyone?
Batteries you can get to to add water or acid to will last you longer and give you better service. ‘Sealed’ batteries are nice, but they are for ‘cars’ – if you want real batteries, look for old Batteries being sold surplus from your power company. You can pick these puppies up for pennies on the dollar, but remember most need to be moved before they close the yard (with VERY few exceptions).
ASK; WTF DO I NEED THIS TO DO AT A ****MINIMUM***** ???? Double that. Listen to Experience. You won’t get hot water, but you might get a jet-pump to gravity feel your house if you can or bought water sensible DOWN AQUIFER from your ‘house’ or spring/stream heating it is a piece of cake with iron pipe grating and storage. next on the list is light — and with LED’s today you probably won’t need your Aldan (brand name) until you do. Get one. Yes they are expensive, guard the chimney because they are hand blown – just trust me on this one. Need Ice? An old ‘ice shed’ should work where it gets cold enough to get even a foot of ice – our house still has it’s ‘ice room’ where we’d slide the ice once it stood out in the freezing night air about two days to freeze a 10x10x1 slab of ice. – and a 20x10x16 foot insulated room will give you enough ice for most – not all, most of the summer.
And like anything else on the ‘prepper’ list – if you have not done it with your own two hands in day light with no pressure – you’ll be worse than worthless when you need it most. That’s why Fire Departments drill at least once a month, even if they have two fires a month – to keep rusty skills cleaned up. I was a Corpsman/Paramedic – and after I’d decertified, yep, I put a sling on a roll-over pt backwards (pointy end toward the hand, not the elbow). I’ve done a sling about 1, 000 times if not more. I was looking at his buddy when I did that – something else you NEVER do – eyes on means EYES ON. Not assessing another pt from 10 feet away while I ‘just finish up here’ – I owned a Series IIa Land Rover – anyone who owns one will tell you that you BECOME a professional mechanic if you own one – but they’ll never not run, unless YOU screw up. Spark at the battery? Anyone? —
See? you do that ONCE with your solar system, kiss it good by. GET it checked, see how much you can do without messing up – then hire out the critical parts and you’ll see they are not the critical parts, they just take paying attention to. Pay someone to do the paying attention for you WHILE they make YOU do the work. You are buying insurance from screwing up. Ditto our Wind-system – my friend mounted our old non-exotic metal magnet on a tower that would NOT take the stress and torque if a good burst of wind off the bay on a stormy February night. He works at Lawrence Berkeley Labs where he now works with various forms of ‘home’ energy. He had a couple of friends check him out – the tower that looked good to him, would take only 1/2 the strain he thought because his guy-wires were not ‘wide’ enough to form a good stable ‘triangle’ to hold it in place. But his friends said – tack some metal here, here, and here, and you are good to go. In August, well before the peak-ridge wind speed of winter. His photo-voltaic system was the same – it’s one of the things he does for a living at work, but he wanted a second set of eyes (and he’s the one who’d be YOUR second set of eyes) – and yes he’d done it all right, though they did suggest a few spots where there was weakness, mostly in soldering, not in design.
Commenter LE Hensen is absolutely incorrect regarding LiFePo4 being explosive – it may be lithium but is a different chemistry from Li-ion chemistry in cell phones and is actually the safest battery worth mentioning out there.
They can be had now for a little over or under a $1/ah – from both US resellers and direct from alibaba.com – I like the 100ah or 200ah 3.2v stringed 15 in a group for @48V (most inverters want 48V). The Outback Radian is an awesome inverter/battery charger – it will handle your wind or solar or generator input, input from your batteries, charge your batteries (settings for LiFePo4 included), grid-tie and go off-grid – so far, the best I’ve found. 4000W and 8000W versions. Each battery normally needs a charge module, which are cheap. The latest gen of LiFePo4 can typically handle 2000 charge cycles. 1/3 the weight of lead acid. Nothing nasty or leaking. Better fail rates than lead acid.
Even if you are old schooling it and don’t want computer controlled anything, they have different characteristics than lead acid and must be approached differently, but you can dispense with computer controlled chargers if you are savvy as their charge and discharge characteristics are very flat and predictable.
Overdrain your lead acid and watch how long they last! LiFePo4 don’t care.
Jim is correct to some degree. Heat buildup in a conductor carrying DC is greater due to the fact that DC Current (Electrons) flow through the wire as water through a water hose with no transition from peak through zero. AC current (alternating from positive peak voltage through zero voltage to peak negative voltage) produces less heat because of less than peak voltage approximately 2/3’s of the time and AC current travels on the outside of the conductor (which cools faster) an not on the inner core (which doesn’t dissipate heat as well). As the frequency increases less and less of the inner core is used (called Skin Effect).
Always size conductors for Maximum Possible Current should a short occur (and there will be shorts, I’m in the business and make a good living at it).
Make no mistake. Solar power will NEVER pay for it’s self (with current industry standards) based on the cost of paying for power used from the Utility Company. Consider the cost of the system up front. How long would it take to pay for it based on your Utility bill? Now throw in backup batteries that have to be replaced on the average of 3 1/2 years (some better but not expected). Also consider the overcast days that your batteries don’t get recharged. The companies that are advertising heavily can not follow through with their promises and homes that have had the installed end up with a system that tends to be 1/2 the size needed to have the quality of life expected. With current industry standards/products, We DON’T do solar well. It can be an alternative to no power but don’t fall into the trap that you can save money by converting.
I’m old man and have tried many avenues of solar. At one time I had two 3 ton solar air condition units in my home. Read everything printed in surrounding libraries including the state university library. After all review of the calculations I came to the conclusion that I could save $ by installing them. What wasn’t included in any of the research was the power to run all the hot/cold water pumps. The power consumed was 1/2 the cost of a typical 5 ton AC unit (which was the cooling needed). The short of that story was, all cost included would have labeled the research a failure (government funding was at stake).
Lesson learned! Scammers come in all disguises (even collage professors).
Lowell
Just thought I’d throw this out there. People with electric golf carts can use the batteries on them in an emergency. I have a 48 volt system with (8) 6volt deep cycle batteries on my cart.
Can you point me in a direction to get some information about getting started taking my home off-grid? Seems like there are a lot of schlocky solar companies around and i’d prefer not to get ripped off. 🙂 I have a large home on acreage, outside of Portland, Oregon (not too much sun in the winter and spring) and i’m on a fairly deep well at 650′. It’s a nice home with all the modern amenities, so I need some powerful solar energy to run the whole thing. My electric bill (no natural gas available this far out in the country…yet so I use propane for the furnaces, all 4 of them) runs average about $800/mo.
Any help appreciated. Thx
I’ve bought a generator from sunelec.com, and they have great prices on solar. If you go on a cruise out of Ft Lauderdale, you can stop by their office and warehouse. Prices now are 20% of what we paid in 2003 (1/3 after the Fed/CA state rebates at the time).
Good article, lots of great information. As far as the wiring size I think larger sizes than he calculated were due to the fact that DC voltage loss is grater than AC voltage.
Great article. I put together a small 200W system like this. I have 2 100W panels, 4 50 Ah batteries, and a 3500W modified sine wave inverter. Some notes on my system:
The Panels: I got these from Home Depot and they came with free delivery and a good warranty. I liked dealing with a company I know. I built a simple frame/stand for them from PVC pipe and they’re sitting on my deck. I didn’t have to mess around up on my roof, and they’re portable.
The charge controller. There are a lot of cheap controllers out there but I got a Morningstar SunSaver MPPT (Maximum Power Point Technology) controller. This was around $200.00 but I think it is worth it. Basically, the MPPT controller will get more juice out of the panels and into the batteries. The panels I got even specified to use an MPPT controller.
The Batteries: I went with lead acid AGM (Absorbent Glass Mat) batteries. Again, the AGM batteries are not the cheapest, but they are sealed, zero-maintenance, can be used in any position and should have a longer life than “flooded” lead acid batteries. Good luck with the LiPos, I’m jealous!
The Inverter: Mine is a modified sine wave inverter I got off eBay, not a true sine wave inverter. The true sine wave are much more expensive. Some things, especially electronics, will not run off of the modified sine wave inverters. They want true sine wave A/C and they won’t settle for less.
As for what I can power the most important thing is my well pump. I can only run it intermittently, but I’ll have clean, potable water. I can also recharge rechargeable AA, AAA, 9V, etc. This gives me batteries for LED flashlights and lanterns, walkie-talkies, radios, etc. There are small 12V coolers available. If you have someone in your family that depends on medicine that must be refrigerated this might be crucial.
if buy chance some one sees this post
I don’t know a lot about this but I do need help to get what I think I need….
I want to run a double door fridge 8 to 12 hrs a day ——- nothing else will run of this panel
On another set up i want to run small hot water heated for a few hours in day time , 3 light bulbs 3.5 hrs at night
Washing machine when needed during day light hrs
and small items here and there like ..box fan car radio AA & AAA rechargeable battery
and a small 1 eye electric cooking eye some and not all at once
Please e mail back if you have any thoughts on this
[email protected]
A couple comments regarding wiring. One thing you didn’t mention is with failure of Inviters/ Controllers is high current draw. Wire/cables attached to a source should always be sized to handle the maximum current supply should a short occur. Most battery packs used in solar applications have a fuse in the battery supply that can limit this current at maximum draw but a downsized cable may not blow the fuse. Then it can become as filament in an incandescent light bulb and possible start a fire. I have pictures of Battery Backup units with shorted invertor/controllers where the battery cases have melted from the load. Never undersize wire based on the expected current draw but on the highest possible current.
There was also a statement regarding Invertor/Controllers with an internal battery which would help start a motor. I have not read the specs on the unit you described but almost every appliance containing a motor will supply the LRA (Locked Rotor Amps) and RLA (Run Load Amps) on the government required rating plate. The LRA of almost any motor is in excess of 40 Amps, some times lasting as long a 2 seconds. 120V X 40 Amps equals 4800 Watts and that is just the Load. There or other current draws at this time that come into play with overload of an Invertor. At this point the actual current draw for the system would be in excess of 6000 watts due to internal I2R (I Squared X Resistance) losses of the supplying system (and thus the failure of Invertor components as you mentioned).
You are right about 50/60 Hertz motors. Most of all late model appliances are built for multiple frequency applications and will be indicated on the Rating Label. While they will draw slightly higher current at 50 Hz, their design allows for this frequency as well as 60 Hz. All may not be lost with your early purchase of the European Invertor.
Invertors produce a Square Wave output unless, as you mentioned, one purchases a much more expensive unit to produce a true (or modified) Sine Wave. Older appliances, especially motors and wire wound components, can and will be damaged with a square Wave Power. Because a Square Wave Reaches the Peak Voltage (almost) instantly, more spike protection has to be considered in the design of the unit. This was not considered years ago.
I always look forward to your articles and am applying many of the slowly. Please keep up the good work.
Lowell
Thank you for the info. From my previous research, I have to agree on many of your points – the rest is new info to me. I did read from several different sites that the best Amp/$ value is in deep cycle batteries; namely golf cart batteries. The 6V cells are usually the most efficiently priced containers, and most people stack them, both in parallel and in series. A 48V system is universally accepted as a good strong supply voltage – of course, you need the correct inverter for that – and parallel connections, as stated, provide the amp-hour / improved wattage capacity. Another downside of building a system too big is that sooner or later, one of your batteries will start to fail. Unless you have a way to check the batteries individually, and often, such a battery failure battery can cause all other batteries attached to fail prematurely. A “smart” system will likely catch the problem early, and will undoubtedly be worth the extra cost.
Use the LARGEST wire you can afford! Why? lower losses @ power loads!!! Use motorhome deep cycle batteries or better yet 2 volt wet cells, in series is BEST. Sealed lead acid are NOT a good choice! LI should NEVER be used, as they have a tendency to BLOW UP – must use an expensive COMPUTER controlled charge!!!! Solar Panel choice is far more important – separate SQURE cells, under glass are SUPERIOR and used on ALL Space Vehicles . . .for maximum watts/size! Inverter choice IS far more important – from 96% down to 10% efficiency, at load!
PS Author of article, please call for correct information…
The largest wire you can afford lol. Like an extra 30 cents a foot is going to break you. This is why it is imperative to do your own research. Very few people are running two volt batteries and space vehicle panels, but this guy seems to think that there is no other choice…because sealed batteries explode dontchaknow.
The gentleman is correct, use a larger guage wire because heat reduces the efficiency of the system, and has the potential to ruin your system. The larger wire will help keep heat build up from occuring. As far as your comment on the number of batteries, I design on grid and off grid systems professionally. I have installed more than one system for off grid preppers with up to sixteen batteries for a prepper with a family of 12. These were solar rated batteries. The readers comments on batteries were spot on. Standard lead acid batteries, auto or marine deep cycle have thin plates in them. Batteries made for solar use have plates twice the thickess. You MUST maintenance your batteries whether they are in use or not once they are hooked up to a solar system. There are a whole host of other dangers when hooking up batteries regardless of type in series or parallel that you MUST be aware of. You can not only damage the system but you can blow up the batteries or electrocute yourself. Keep in mind also, that when you are designing your system, you have to have a system and batteries that is balanced so it will charge and allow for dischage at the same time so you have power while the system is charging. My best advise is get professional help in designing your system. I am not saying that to bring in more business, I am saying that for the sake of keeping folks safe. You have not even touched on proper venting, the fact that batteries should never be used in the same space you are living in, particularly a small confined space. Most batteries give off gases which can prove harmful or even fatal if not properly vented. This does not mean you have to have someone come to your place to install the system, but most professional installers I know will be more than happy to help design a proper off grid system for a nominal fee, and instruct you on how to hook it up, and can help you purchase the proper products for your system, or give you a list.
I was thinking of a solar system for an off grid travel trailer. I went to Sun and Solar in flagstaff AZ, and the fellow there printed up a list of every solar panel, batteries, controller, inverter, part, wires, connecter, fuse, etc. that I would need, and would include a diagram of how to put it all together. Said I could do it myself, and if I had any questions, just call. All this at No cost. 5, 140W Kyocera panels, 4, 260 AH 6v golf cart batteries, 2000w pure sine inverter, 60 amp MPPT controller, and everything needed to connect it, $3600.. This is much cheaper than paying park rent for a year, so it is cheap compared to that, if you don’t mind parking at Walmart, or a casino, or on BLM land, or in Natl. forests, or at the beach, or the Lake, or a family members driveway, or many other free places.. Yes, you could use an RV park occasionally, to do laundry, shop, empty and flush tanks, refill water, or shower. But the Solar system will surely pay for itself in a year most likely..