inexpensive solar electricity generation
By on Fri, Feb 22, 2013 - 10:24pm

Hi, I have noted some real great deals on ebay recently on solar cells. It is easy to build your own solar panel with only a modest amount of equipment. The cells that are a real bargain are the seconds or working but cracked or blemished. These cells are still working at levels approaching the perfect cell levels while costing less than 10% in some instances. For example, I saw a dealer selling a bundle of solar cells that will generate 1,000 watts of electricity for $100. The cells have to be connected and placed behind glass to use them but with some effort the home builder can make his own solar panels and harvest solar electricity for much less than the commercial panels. For example, commercial cells use many fairly expensive components which allow the panel to achieve very high efficiency. However if some degradation on performance is accepted then the inexpensive glass from the local salvage yard and supplies from the local hardware store can be used. Cell potting compound is very expensive and I suspect that the silicon caulking compound that cures and releases ethanol may be a suitable but lower performing level substitute.  I have not tried this yet but it should work well. Silicon caulking compound is not nearly as clear as sylgard, the commercial solar cell potting compound, but is a fraction of the price. The less than perfect clarity of caulking compound is offset by the price of the caulk as compared to the sylgard.

Information on building panels is available on the web. One note, I have never understood the reason for putting protection in the form of mats or barriers on the back side of the potted solar cells. If the panels are mounted then they will not recieve any impacts from the backside so impact protection for the backside of the cells is an expense that I will skip. The barriers used to protect the backside of the cells from mechanical damage are rather expensive too.

Best Regards



markf57's picture
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Off grid only

If you go this route, it will only work for an off grid system. There is no way in the world any utility is going to allow and non UL listed or homemade panel be grid tied.

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Other places to source cheap solar panels

I suggest you to visit . It has a repository of solar panel manufacturers,suppliers and you can source cheap panels and other accessories from them.Hope this information is useful to you.

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Need "Solar panels for Dummies" level guidance

When a newbee (like me) comes to an entirely unfamiliar arena (like homemade, inexpensive, off-grid solar panel systems for a home), a guide is needed that begins at the beginning and steps through the thought process, equipment selection, assembly, wiring diagrams, etc.

Anyone aware of "start at the beginning" type of guide on how to do this?  How do we make it expandable?  How would you mount this on a shingle roof?  How big a system would be neede to run one large freezer? What tools are needed to connect it, monitor current and voltage?

I have frequently gotten wonderful assistance at the rank beginner level here on PP and greatly appreciate the help offered previously.  :-)  Or pointers to other DIY projects on the web.


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Wendy S. Delmater
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expandable system


What we've done thus far is buy 3-panel solar power kits from Northern Tool. We bought staock alumiumn channel and have a hand rivet tool: we cut the stock to make a rack for the panels that had the right toilt to catch the sun most of the time, and then riveted it together.

We have a source for used but still serviceable Uninteruptible Power Supply (UPS) batteries. This were used for computer back-ups, but are deep-cycle batteries like you need for solar. A wire runs down to to batteries from the solar panels through our dining room window to the battery setup on a side table.

If you PM me I will have my husband explain how he tied the whole system together. And there is a whole thread on this is the forums:

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Wendy - question on batteries

Wendy,  Is it fair to assume that the batteries you are using are some kind of AGM (absorbed glass mat) or Gelled rather than flooded acid Lead type batteries?   

I would not keep a standard, flooded type Pb acid battery indoors, if that's what you are doing;


AGM's do not have any liquid to spill, and even under severe overcharge conditions hydrogen emission is far below the 4% max specified for aircraft and enclosed spaces. The plates in AGM's are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery.

Even with all the advantages listed above, there is still a place for the standard flooded deep cycle battery. AGM's will cost about 1.5 to 2 times as much as flooded batteries of the same capacity. In many installations, where the batteries are set in an area where you don't have to worry about fumes or leakage, a standard or industrial deep cycle is a better economic choice. AGM batteries main advantages are no maintenance, completely sealed against fumes, Hydrogen, or leakage, non-spilling even if they are broken, and can survive most freezes. Not everyone needs these features.

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They're all gel-sealed.

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Good Info

Wendy S. Delmater wrote:


What we've done thus far is buy 3-panel solar power kits from Northern Tool. 

What are you able to power with this system?  It sounds like a good way to get a feel for solar.

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recharging station

We are currently recharging three cell phones, a Kindle and a laptop from a power strip attached to only the solar panels. On cloudy days I charge the laptop elsewhere, just in case, but the only problem we had was when a battery failed. A battery tester is a must.

Here is a similar solar panel kit at Northern Tool. It now comes with its own metal rack, it seems. 45 watt:

60 watt:

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Site Especially for Do-It-Yourself Solar

For the last couple of years I have been learning to build solar systems to power my storage/work shed. This low priority project became much more urgent after reading The Crash Course.

With the help of many like minded solar system builders of small to whole house systems, I have expanded and enhanced the system to be able to run a small freezer, microwave, chargers and other loads(not all at once).

I would highly recommend this site for very supportive advice, affordable sources and a knowledge base for however far you want to go in solar systems. They are not selling anything. Totally suppported by membership which is free.

They were a spin-off from Harbor Freight but are not sponsored or supported by them.

Check out :

PS: I have a Word document with descriptions and pictures of my project for anyone interested.

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Go bigger if possible...

The problem with the kits like those from harbor freight is that they are not designed for long term continuous use and do not provide that much power.   Unless you are renting, just experimenting with solar or are on a shoestring budget I would really look at some of the larger systems.  Here is an example supplier of some kits (I'm not affiliated with these people nor have I used them):

Affordable Solar - Off Grid Kits

The kits generally include roof mounting hardware, modules, inverter, and charge controler and battery (if off grid).  In addition you get to claim federal 30% tax credit because it's interconnected to you house (unlike the smaller kits).  You may also have state, local, and utility incentives available to make the cost easier to handle.  Often you can get financing for them as well.

One other advantage is if you start with the smaller kits, you can add modules to the systems over time (up to the capacity of the charge controller/inverters).

Yes - I realize the cost of these kits is more like buying a car as opposed to a TV - but you get a lot more power and hardware designed to last 10-25 years of continuous use.

The low cost kits are a great way to experiment, generate a little power for things like cell phones, laptops and are definitely better than nothing, but if you want to power things like fridges, household appliances, and lights I would seriously look at the more traditional house solar systems DIY kits.

As far as making your own modules from cells. That really seems more like an experiment than a way to put together a system.   You have to consider that the solar module market is well served and competitive. Do you really think you can build a module that much cheaper than a plant designed to crank out thousands?  Yes, you can cut corners but it may bite you in the end if you are really relying on the power.  The big issue I see is finding impact resistant glass to survive hail storms and keeping the module sealed against moisture.  

Jim wrote:

I have not tried this yet but it should work well. Silicon caulking compound is not nearly as clear as sylgard, the commercial solar cell potting compound, but is a fraction of the price. The less than perfect clarity of caulking compound is offset by the price of the caulk as compared to the sylgard.

You need to keep in mid that with crystalline solar cells, a little loss of clarity may result in a considerable drop in power.  Just a little shading over one cell in series effects your entire module.  If you do this experiment please keep us informed, I'm be curious how it works out.  Here in ABQ there are classes for making your own panels on occasion, you might want to check with a local hacker space to see if anyone offers things like that in your area.  It might save you some experimenting head-aches.

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starting out

I started out much like Wendy it sounds.  First just playing with a couple panels my dad gave me that he got from Northern Tool.  Then I got the 45 watt kit from Harbor Freight which looks to be the same as what Wendy linked to.  For my first array I ended up buying 6 of these kits and tying them all together for a 270 watt system.  This did involve needing a more significant charge controler.  I also got a pure sine wave inverter to be able to change the DC power of my battery bank (AGM type) into AC power as clean or cleaner than what you'd get from the power company.  Later I added two 125 watt 12 volt "real" solar panels onto this system.  The charge controler I had bought was rated to be able to handle this extra power with no trouble.  This fairly simple system has been powering my metalsmithing studio for several years now.

Just this past weekend my new array was finally hooked up.  I hired a professional company to do the design and installation of this one.  It is to power my home and allow me to go completely off the electric grid.  I won't say this was the cheapest way to go, but for powering my whole house I wanted to make sure it was done right, and all legally permitted and to code.  I've been learning more from seeing this one put together and I now realize ways I could make my smaller studio system more efficient.

I did want to note that if you are looking for cheap solar panels the Harbor Freight/Northern Tool kits, while once fairly cheap comparitively, have now become quite expensive.  Their prices haven't actually changed, rather the costs of other type solar panels have come way down.  I now think of these kits as more like solar toys.  (Mind you, those "toys" are still powering my studio just fine.)  They can be a good way to get your feet wet and play with solar, but they cost $4+ per watt.  I've been seeing solar panels frequently priced under $1 a watt now.  I've actually seen them as low as 65 cents a watt on sale, and this is before any tax credits!  I'm not at all affiliated with them, but where I've been seeing the best prices has been at  This is where I bought the panels that make up my new array to power the whole house.

While one could buy the cells cheaper and assemble the panels yourself, for me the time involved in doing so just isn't worth it compared to panels at under $1 a watt premade.  Though it does sound like something fun to do if I had more spare time.

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Cheap Panels

I have been following solar panel prices for some time, from back in the times when they were $10/watt or $5/watt. 

One of the best sites I know of is I just checked. They have new polycrystaline panels for 88 cents/watt in pallet loads, and $1.01 for single panels. They also have grid connect system with inverters for under $1.50/watt (without mounting hardware).

With the federal tax credit of 30% that takes complete solar systems to around $1/watt. 

I've run the numbers for my area and that makes the payback period against line power rates as around 7-8 years for 25 year panels. At this price these are really competative to line power and folks should consider them as a complete alternative to line power not just a fallback system. A pretty decent system is less than $10K that would handle a whole house (if you don't use electric heating and have gas for cooking.)

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Avoid "Homemade" and Harbor Freight Solar-PV Modules

I subscribed on Dr. Martenson's website here about 4 years ago; but, I'm brand new to this group.  In the spirit of helpfulness, I'd like to make a few comments related to previous posts in this thread...

Don't waste your time and money building homemade solar-PV modules ("module" is the proper term, as opposed to "panel").  There are (at least) two reasons for this:

  1. A solar-PV module is a single series string of solar cells.  If there is any small break in that series connected string, at any place within the module, the entire module is dead.  If you do not completely remove all the flux, if you do not have consistently good solder connections, and if you do not perfectly seal the cells for any infiltration of moisture, your module will suffer a short life.  Properly manufactured modules are precisely assembled with robotic arms in a clean and controlled environment.  The soldered cells are also sandwiched between two layers of ethylene-vinyl-acetate, with all air and mositure drawn our via vacuum and then melted together, encapsulating the module circuit.  Manufactured modules are also shielded by proper glazing material and are framed with extruded aluminum rails for rigidity (if modules are flxed or bent, cells can be cracked into an open-circuit condition and solder joint can be broken into an open-circuit condition...dead module).
  2. The cost of manufactured PV modules is down to $1.00/watt of rated power, and lower from some suppliers.  These quality modules are made with proper materials that allow for typical warranty periods of 25 years.  They've also been tested prior to sale, and they have been built to and certified to meet all the safety and quality standards set by UL, IEEE, FM, IEC, etc.

Don't waste your money buying the low-quality "junk" sold at Harbor Freight.  If you're set on doing this, realize...

  1. you're buying an inferior product; and,
  2. you're probably paying a higher per-watt cost than if you bought proper PV modules from a reliable vendor.  I just went to their website to check:  their 15W, 12V module is presently marked down from $80.00 to $60.00 -- that's $4.00 per watt!  More importantly, 15W is miniscule -- don't have too high of expectations for what you can do with something this small.

Regarding batteries...

  1. It's perfectly fine to have flooded-cell Pb-acid batteries indoors IF you do it properly.  It's also dangerous to have gelled-electrolyte or AGM batteries indoore if you do NOT do it properly.  Keep in mind, there are three hazards presented by battery storage:
    • Electrical hazard (which can be a shock hazard and/or a fire hazard) --  Terminals need to be isolated/protected from casual/accidental shorts (+ to -).  There should also be a properly-sized, class-T catastrophic fuse installed at the (+) terminal before the battery circuit connects to anything else.  Your tools should also be made battery-appropriate -- cover them thoroughly with vinyl tape or rubber to prevent accidental shorts between (+) and (-) terminals.
    • Chemical hazard --  The electrolyte is sulfuric acid.  This can cause severe burns and blindness.  If you have a battery pack, you should also get several large packs of baking soda from Sam's Club and keep it handy, just in case.  It's also handy to keep a 5-gallon bucket with water and soda-mixed-in that you could dowse yourself withm just in case you get splased by acid.  Also, always wear (at least) safety glasses when working with your batteries.  Better yet, wear a full face shield, a plastic/rubber apron, and rubber gloves.
    • Explosion hazard --  All Pb-acid batteries out-gas H2 (hydrogen) when they are near to being fully charged.  Fortunately, H2 can easily escape from just about any conventionally-constructed room (Warning! Do NOT put batteries in a tightly-sealed space!); and, H2 is not explosive until it hits a concentration in the room of 4%, by weight.  "Sealed" batteries have a special recombinant element in their caps that prevents/limits the loss of H2.  There is a BIG BUT here, though...if your charge controller is not properly set, the voltage of the batteries can be drivien too high, forcing H2 out.  This will not only create a potential explosion hazard, it will also boil off your electrolyte and destroy your batteries.  Regarding "flooded" cell batteries, you can buy special, aftermarket caps for these that do the same thing as the recombinant elements used in "sealed" batteries -- Water Miser caps and Hydrocaps.

Get good quality training, even if you're just going to be a user/owner of a solar-PV system...

  • Make contact with the Solar Energy Society in your State, if you have one.
  • Go to a quality, reputable Renewable Energy Fair where they have workshops and experienced users and installers.  The best on the planet is heled every year in Custer, WI near the summer solstice.  It's the Midwest Renewable Energy Fair, sponsored by the MREA (Midwest Renewable Energy Association).  You can get info on the fair if you Google "MREA Energy Fair."
  • Take a workshop or training course from an IREC/ISPQ-accredited training program.  In the Central US there are three:  the MREA in WI, the Evergreen Institute in MO, and Kankakee Community College in IL.  Out west there is Solar Energy International in CO, and Lane Community College in OR.

I hope this is at least a tad useful to folks here.



David Huang's picture
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Thanks Tim

Thanks Tim for sharing all that information about solar modules and batteries.

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Don't Build Your Own Solar Panels

Solar panels have the longest useful life of any of the components used to make a solar energy system and commercially manufactured panels with all the quality and performance certifications have never been less expensive.  And, assuming the manufacturer stays in business - you have a 20 or 25 year performance guarantee.

Regarding price, 12 volt solar panels over 100 watts are not a good value compared to many different 220 to 250 watt 24 volt panels.  Last year's trade dispute between the USA and China increased the price of and reduced the availability of larger 12 volt panels.

24 volt panels in the 220 to 260 watt range presently give you the most energy bang for your buck.


130 watt 12 volt 7.56 amps (the amps are what is important - amps do the work)  $280 approximate selling price

250 watt 24 volt 8.3 amps  $280 approximately, there are many panels less than $1 a watt

If you use an MPPT charge controller (maximum power point tracking) to charge a 12 volt battery from the 24 volt panel you get 16.6 amps for the same money.  The MPPT controller costs $170 or so more than a PWM (pulse width modulation) charge controller, but is cheaper than 2 130 watt panels.


Ron Castle 

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Notes on My "Solar" Project

I have been working on my "solar project" for a bout a year now. I started at the back-end first- have installed a 2400 watt 24 vdc/120vac inverter charger in the utility room near the panel, along with a battery bank consisting of 4 Trojan t105 flooded bats. The inverter is currently hard wired into 2 circuits- the one for basement lighting, and an upstairs circuit to power my Significant Other's oxygen concentrater. (She is on O2 for a med. condition)

The system as is is basicly acting as a UPS for the O2 and gives me basement liting to make hooking up the 5kw portable gen a lot easier in a power outage; I calculate that the 5kwh of battery capacity will run the O2 concetrater for about 8 hrs min. with no generator. Also added a transformer which gives me 220 vac and enough guts to run the well pump for a few cycles.

Recently purchased 4 140w 12v solar panels and just ordered an MPPT controller. Ultimately planning to wire the panels for 48vdc and use the MPPT to optimise charge.

Main reason I went with 140w/12v panels- handling, and shipping. UPS (United Parcel) will deliver this size but bigger ones need a truck shipment ($$) so it doesn't make sense to order just a couple that way. Also, the 140w/12v panels are 5 ft long and weigh 35 lbs each- about as much as I want to hoist onto the roof without pro help. May try to install this spring, but I wanted to have them now in case shipping gets iffy one day.

Tried my hand at building a solar panel but the whole project became too time intensive and I didn't have a good local source for tempered glass- was going to use hardware-store window glass but decided it was a bad idea!

More later!


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Time Out, Marc!

I may be misunderstanding this statement (quoted, below).  If so, my apologies:

"...have installed a 2400 watt 24 vdc/120vac inverter charger in the utility room near the panel, along with a battery bank consisting of 4 Trojan t105 flooded bats. The inverter is currently hard wired into 2 circuits- the one for basement lighting, and an upstairs circuit to power my Significant Other's oxygen concentrater."

Are you using a DR2424 inverter, or it's newer incarnation, the TR2424?  I'm sitting here hoping you have your inverter's ac-output wired into a "critical load panel" instead of creatively and directly tying it to branch circuits in your main panel -- otherwise described as a sub-panel of your main panel.  Is that how you did it?  I hope so.  If not, you may see fault code F07 come up, and your inverter output will shut off (if not be damaged).

Just checking...

ponytail_guy's picture
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TJ- The inverter is a Xantrex


The inverter is a Xantrex TR2424- the ac input is from a dedicated breaker in the panel (marked "charger") and the output has 2 "branches"- one goes to a mini 2-breaker box which feeds the 2 "critical" circuits- I pulled the lines from the main panel and connected them to the new breakers; they can only be fed from the output side of the inverter. To test the configuration I shut off the "charger" breaker and the inverter kicks in immediately powering the desired circuits.

The other branch from the inverter is wired through/past a transformer (2kva I think) which is configured as an auto-transformer- 120 vac goes into one leg and center tap of the primary, 220 comes out two legs of same, the center tap is now neutral: the secondary is some odd voltage for an industrial application so I just insulate the terminals. This is connected to a short length of 10ga. 4c cable with an L1430C female twistlock plug on it- same as the extension "cord" on my generator. This config allows me to power things like the well pump and any circuits in the house on either line, without having to short things out to make it work.


tjwilhelm's picture
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Good for you, Marc!

Seriously, I'm glad to hear you did it this way.  I can't tell you how many DIY nightmares I've run into.  Some just won't work.  Some will damage the hardware.  Some are unsafe.  I always end up feeling bad for the person who goes forward with enthusiasm and then ends up discouraged and depressed, albeit educated by the experience.  I'll just feel gratefully happy for you.

Thanks, Marc...and best regards!


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Thanks Tim! I appreciate your

Thanks Tim!
I appreciate your concern- I have been involved in electricity and electronics for my working life (work in industrial automation now) but I am not beyond doing something stupid. Fr'instance, when you torque down the nuts on the terminals on the T105s, there is a big difference between 100 inch-lbs and 100 ft-lbs. Need any almost-new T105s with no studs?... I am keeping them "fresh" on a desulphating trickle charger for when I figure out a way to fix them. Really hated to buy a second set of them to finish the project, but it is the lesson I paid for! I am sure further lessons lie ahead....


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