1. Item Details:
You can buy this solar cell individually. Usually we prepackage them in to 36, 50, 72, 108, 150, 200 pieces and sell them as a bundle. But this one you can order any number of cells you want. The unit price is higher because people usually buy a few as samples to find out how well they perform and how they look. We are very confident in the solar cells that we sell.
This batch of solar cells came from the newest factory in Devens, MA directly to our warehouse in Silicon Valley just a few weeks ago. This set of new 3"x6" solar cells are string ribbon multi crystalline cells and have the smallest carbon foot print - they waste the least silicon in making these cells.These newest cells have a little different look from the other cells are still being made in the largest quantity in German factory (The German factory uses all American technologies and equipments, and it's adding another new production line going live this year). The front of the solar cells looks similar to the traditional multicrystalline solar cells in that they show the borders and shapes of irregular crystal formation. In terms of output they may be slightly better, but in any volume production you are going to have cells with varying levels of power output. The cells are the original factory standard cell size, not other sizes cut by using home made tools which could damage the cells during cutting process. The cells have never been used or soldered, and are not recycled from badly made panels like some factory installed tabbed cells are. There are no tabs on these cells so you can start from scratch and get experience in making solar panels. In our listings, if we don't describe them as 'chipped', then they are considered to be our category A cells, although very tiny defects or blemishes could exist but they don't affect power output. Our sorting team tries to do as good as a job possible to categorize the cells. Almost all of customers have been very happy with the solar cells that we shipped in large volume. If you think the solar cells don't meet your expectations, send them back within 7 days for a complete refund or replacement, because we understand that in large volume order processing, some mistakes do happen and the important thing is that we are willing to rectify them and we need to be given an opportunity to fix rare mistakes when they do happen. From the enormous number of cells that we shipped this past couple of months, returns have been essentially negligible. We will keep rolling out new products and categories at great prices and those who mistreat us will be excluded from our new offers.
The following is a little more details regarding this listing:
The facgtory standard cell specifications are the following, though the individual cells can be above or below these standards. We do not guarantee that each cell will perform to these standards, however, our customers have been happy with what they get.
Cell Specifications: Average Power (Watts): 1.75 Wp Average Current (Amps): 3.5 Imax Average Voltage (Volts): 0.5 Vmax Thickness 200 µm = 0.2 mm Exact dimension: 3 1/4 inches x 6 inches, or 80 mm by 150 mm Weight: Just above 6 grams, or 0.2 oz.
II. How to make sense of the above numbers:
The basic and very important formula you need to know to make sense of solar cells is this: Power (P) = Current (I) Multiply by Voltage (V), or P=I*V Power's unit of measure is watt, Current's unit of measure is amp, Voltage's unit of measure is volt.
So in our solar cell's specific example, if each solar cell is rated at 1.75 watts on average, and the voltage is 0.5, you do a little algebraic math, then to get the amps (I), since P=I*V, so I = P / V , therefore I (amps) = 1.75 watts divided by 0.5 volts = 3.5 amps.
It's important to understand the concepts of series connection and parallel connection when stringing these solar cells together to make a solar panel. Series connection of the cells increases voltage but not amperage; parallel connection of the cells increases amperage but not voltage. Series connection is when you connect the positive terminal of a cell with the negative terminal of the next cell. Parallel connection is when you connect the positive terminals of all cells in the set of cells with a tabbing wire and all the negative terminals of all cell in the same set. You can use a combination of series and parallel connections to get the right voltage and amperage for your solar panel.
The cell specifications above were given to us by the manufacturer as averages. Variations are possible. To make a 18 volts panel, for example, you connect 36 cells in series (36 cells times 0.5 volt each = 18 volts). And 36 * 1.75 (each cell in theory averages 1.75 watt) watt = 63 watts. The amps you will be getting is 63 watts divided by 18 volts = 3.5 amps.
III. Solar cells basics:
The front of the cells (blue side, aka Sunny side) has two thick white lines, called bus bars. They are the negative terminals of the cell. The back side, where the 6 square dots are, are positive terminals. Connect the tabbing wires from the bus bar of the first cell on one side to the three dots of on the back side of the next cell. That way you have a series connection. Repeat the process on the other side of the cells. In panel making you should connect all the tabbing wires on the front for all the cells first, then flip the cells over to solder the back side in a second step. Some solar cells such as SunPower cells have both positive and negative terminals at the back of the cells, but we don't have to worry about them. Most cells are negative on the front and positive on the back.
The thick white color lines, called bus bars, on front and the contact points on the back are made out of silver, and you should keep them intact. Apply solder on your them and the wires should bond. Do not use sand paper to send it down. The most you should do is to use a pencil erase to clean the surface of the bus bar or the soldering points at the back of the cells.
Make sure that you test the cells under strong sun light with the front of the cell facing the sun, at the same time connect your meters to the right terminals. Since the positive side of the cell is at the back side, you can get a metal plate, ideally copper, and place the solar cell on the plate, with the blue side facing the sun. That way you can place your positive lead from your meter on the plate to access the positive terminal of the solar cell, and place the negative test lead from your meter on the bus bar of the solar cell to get voltage and amperage readings. If you are inside the building, make sure you shine your sun simulating lamps onto the front of the cell while testing.
V. Panel configuration:
For those who are new to solar panel making or if you don't have an engineering background, here is our recommendation:
1) Make small panels first so you gain experience.
2) In most situations, make either 36 or 72 cell panels, and connect them in series. 36 cells give you 17.5 or around 18 volts or so. And 72 cells doubles that. These panels are very useful, and you will find a lot of matching products that will want to buy! For example, you almost always want to use a charge controller if you make your panels to charge batteries. Charge controllers usually come in 12 or 24 volt settings, which match your panels' 18 and 36 volts very nicely. Yes, your panel voltage should be 1.5 times the voltage of the battery you intend to charge. Connect more panels together if you want to tie to the grid, in which case, always use an inverter.
3) For a lot higher voltage panels and configurations and system installation, consult a professional. Just don't fry yourself.
If you want to become a serious panel maker, buy a good soldering iron whose temperature can be adjusted. Don't get a cheap iron. It's one of the most important tools you need to have. If you can't get an ajustable soldering iron, get one that's rated at 90 watts. You want your iron temperature to be around 690 degrees F when soldering the tabbing wires that we provide to the solar cells. Always apply some flux on the bus bars or the soldering point at the back of the cell before soldering. It works every time in our lab if you just follow these simple preparation steps.
Disclaimer: We are not experts in power systems and the above are what we learn through experience but we share what we know, and you should take it with a grain of salt. Buy books written by experts or take classes from the pros.
The solar cells are very fragile so be very very careful when handling them. But out of all of the solar cell packages that we sent so far, we have not not heard of a single report on broken cells as a result of our packaging. We invested a lot of resources to make sure that the cells are well protected by a combination of foam pads, paper pad, bubble wraps, inner box, and outer box. We have won rave reviews from our customer feedback on our outstanding packaging, just check our feedback so you can rest assured that your cells arrive intact. Our warehouse personnel take great pride in their packaging. And we are developing even better and efficient packaging solutions to bring the cells to our customers whole.
Each package is clearly marked and labeled with how many inner packs and how many cells there are in teach pack. We also weigh each package and everything is recorded and signed off before shipping. All shipping paper work is double printed - one for our customer and one for our record, so that we have documented proof that we have shipped everything that our customers bought. This is done to prevent suspicious claims of not receiving the goods. In extremely rare occurrences where cells were shipped short, we would gladly make up the cells that you paid for but didn't receive.
You might break some cells during panel making process, so we always give our customer extra bonus cells for free just to show consideration for our customers. The number and percentage of extra cells we give vary, and it's purely at the discretion of the mangement, but all of our customers have been pleased with the deal they get.
We ship the packages via US Postal Service Priority mail, and we buy USPS delivery confirmation for all of the shipments at our own expenses. For solar cell orders that are 250 and above, we buy 'Signature Required' so that you sign of the package as well, unless you tell us not to - we will still buy delivery confirmation for you. This will make sure that you receive the cells. Delivery confirmation will give us a tracking number from which you can see online that delivery has been confirmed, but no signature is required. 'Signature Required' features says exactly that, and it's different from 'Delivery Confirmation' by the Post Office.
4. Product Returns
We stand by the products that we sell. If you are not happy with our cells, just send the cells back in their original packaging for a full refund within 30 days after we ship the goods.
5. Volume Discounts
We welcome wholesale buyers. Please send emails to wholesale@EverbrightSolar.com if you intend to purchase quantities far larger that what's listed in on our online store.