Step 11: Install the Blocking Diode

Each solar panel in a solar power system needs a blocking diode in series with it to prevent the panel from discharging your batteries at night or during cloudy weather. I used a Schottky diode with a 3.3 Amp current rating. Schottky diodes have a much lower forward voltage drop than ordinary rectifier diodes, so less power is wasted. Every Watt counts when you are off-grid. I got a package of 25 31DQ03 Schottky diodes on Ebay for only a few bucks. So I have enough left-overs for lots more solar panels

My original plan was to mount the diode inline with the positive wire outside the panel. After looking at the spec-sheet for the diode though, I decided to mount it inside since the forward voltage drop gets lower as the temperature rises. It will be warmer inside the panel and the diode will work more efficiently. More silicone caulk was used to anchor the diode and wires.
<p>Im using http://inplix.com instructions to make it and I do it already :)</p>
<p>Today just looking ebay diy cell and diy panel cost about 100W 40-60&euro; and what more panel parts buy have cheapen nominal home need 1000W or 4000W but 1000W have under 1&euro;/W save about 1000W 400&euro; because prices have come ewery year down lot. before 1000W cost little up 1&euro;/W now about 40 cent/W nominal prize. ready to use panel cost about 2-6&euro;/W or more, what seller want lie and fool you :D better made diy panel and forget all fool seller.</p>
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<p>I know a solar panels seller website in my are www.electrical.bazaronweb.com but they are not selling solar cells , where to buy solar cells in lucknow, India any idea ? </p>
<p> <br> <br>howdy, your <br> websites are really good. I appreciate your work. <br> <br>Home Prices In <br> Gilbert Arizonahttps://youtu.be/iHMkAQC_cmg</p>
<p>I made it but the cells easily crack and also it makes it a bit difficult. The heat inside the cabinet bends the cells and to prevent further damage I removed it from solar. How to prevent it. I am using acrylic sheet to make window.</p>
<p>Please help me. <br>1. where can i get this solar cells ?<br>2. What is the difference between mono crystalline, poly crystal and multi-crystalline?<br>3. How many pieces of solar cells are there in 1 kg f it?</p>
could i harvest solar panels from garden stakes and solar toys
<p>You *could*, but they won't be very powerful and you will need a very large quantity. Also, if they aren't all the same type, putting them in series will only give you as much current as the smallest one.</p>
<p>thank you for this very nice project...</p><p>I want to ask you if i want to buy the solar cell what must be its power?</p>
<p>I was looking for a higher capacity Solar System (400W or more). I found a really nice instructable. Heres a link<a href="http://www.instructables.com/id/Apartment-Solar-System/" rel="nofollow">http://www.instructables.com/id/Apartment-Solar-System/</a></p>
Excellent project. HOWEVER, if you try to build this keep in mind that you will NOT get 60 watts out of it (as claimed by the author) using the cells that this author used.<br><br>The author claims it produces 18.88 volts OPEN CIRCUIT with NO LOAD. No problem there. This is pretty much typical for 36 cells in series.<br><br>The author claims it produces 3.05 amp SHORT CIRCUIT CURRENT. Again, no problem as this is typical of this size solar cell.<br><br>And it's true that volts x amps = watts.<br><br>However, you can not multiply 3.05 amps short circuit current by 18.88 open circuit volts and come up with ~60 watts (57.584 watts to be exact).<br><br>Why?<br><br>When the solar panel is short circuited you get 3.05 amps at ZERO volts. 3.05 x 0 = ZERO WATTS.<br><br>When the solar panel is open circuit you get 18.88 volts at ZERO amps. 18.88 volts x 0 amps = ZERO WATTS.<br><br>What you need to look at is the IV curve (I=current in amps and V=voltage in volts) for the solar cell being used. When the solar panel is producing the maximum amount of power that it can produce the voltage will ALWAYS be LESS than the open circuit voltage and the current will ALWAYS be LESS than the short circuit current. Do NOT expect to see anywhere near the 60 watts claimed for this solar panel if you decide to build it. Depending on the exact solar cells that you get, expect to see more like 30 to 40 watts under load and you will not be disappointed.<br><br>This author makes the same error in his &quot;How I built a folding 15 Watt Solar Panel&quot; instructable where he also multiplies SHORT CIRCUIT CURRENT by OPEN CIRCUIT voltage and comes up with 15 watts for 40 cells (or 2.67 watts per cell) which is impossible considering that those cells are only capable of producing ~0.25 watt per cell under IDEAL conditions and more like 0.15 watts per cell under typical conditions.<br><br>Again, NICE PROJECT but the author REALLY needs to correct the mis-information he is posting in these instructables and on his website.
<p>you are absolutely incorrect. by ohms law itself. it takes one volt of pressure to push one current of power through one ohm of resistance. therefore 3.05 amps requires at least 3.05 volts. but the ultimate truth you are probably looking for is that direct current CANNOT, WILL NOT, and NEVER WILL BE measurable in watts. to this very day, and i fear, for quite some time the difference between AC and DC will be misunderstood by even PHD holding electrical engineers. i am currently part of a project to rectify the problem. but fighting academia is harder than one might think, unless you consider how many theses for doctorates that would be nullified are taken into account. good job on the instructable. and never trust a PHD. ;)</p>
Good comments. There are way too many Pie-In-the-sky claims made by people who make panels. And, way too many claims you can save 75% off factory panels by making them yourself. I blame all this on the second hand, B solar cell peddlers out there. They try to convince people they can make a solar panel for pennies on the dollar by purchasing their junk cells. Only after purchasing, the buyer finds out that the panel cost is going to be much higher unless big corners are cut.
<p>This came up again in Instructables, I guess this video was made almost 4 years ago. Today you can find solar panels at less than $1 a watt, some as cheap as 60 cents a watt. cheaper than they can be made and they can live outside...</p>
So how many total diodes were used on this?
Hi there, <br> <br>I just wanted to say, I built 20 solar panels because of this instructable, so thank you. It helped me a great deal understand about solar power and saving real cash from buying from the electrical company. <br> <br>Currently on top of my house, there are over 20 panels I made by hand using local materials here in asia using your specs. I bought solar cells from ebay marked as B grade or A grade, almost exact replicas of the images on this instructable. It took over 2 years to complete them (at least for me). <br> <br>There are a few caveats I ran into while building the first panel, which I shortly learned then fixed on the 2nd panel. Then more problems happened on the 2nd panel until what I have is my 20th panel. <br> <br>1) Rain. It rains about 6 months of the year. I used silicon caulk bought from Home Depot., to seal the panels as per your instructions. However, water eventually made it through the wood, regardless how many layers of external paint I applied to each panel and upped the amount of silicon to seal. <br>To solve the problem now, and in the future, I read somewhere else that people bury there solar cells inside clear epoxy. That did the trick. I no longer had problems with water seeping in. However, it did dramatically increase the cost of making the panels. Resin or Epoxy is not cheap even in big quantities. <br> <br>2) Plexi-glass didnt cut it. It immediately warped the the shape and size and domed. I replaced the plexi-glass with standard window glass cut to size. <br>Due to the other 6 months, where it doesnt rain, nothing but pure hot sunlight. <br> <br>3) Amperage is dropping over time. My panels are giving me an open voltage between 18V and 21V. Under load, the voltage drops to around 13.7. (when everything is all connected) The amperage is dropping on some of the panels <br>The amperage varied when first built gave around 1.8 amps to 2.4 amps. <br>Now each panel 2 years later, dropped to 1.1 amps to 1.6 amps. <br>That's a pretty big drop in total amount of wattage. Its also a huge red flag to anyone building their own panels. <br> <br>4) Repair. If you ever need to repair the cells, you're going to need to open up the panel. For areas that doesnt have extreme weather, resin/epoxy is probably not necessary. But at first, one of the instructions was to glue <br>the solar cell to the wooden backing, so that it stays put. I'm sure this instructable, never thought about having to repair the panel itself. But gluing the cell to the wooden backing is an absolute no-no. Not only is it frustrating hard to remove, it is almost impossible ( at least in my own experience ) <br> <br>Anyways, thanks for the instructable. Im not sure if DIY is a good way to go now, now that I learned more about the process and building them. The factory stuff bought from the store is already pre-made for outdoor environments. The savings between a panel and building your own these <br>days is negigible. <br>

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