I: Item Details:
These untabbed 3"x6" Devens solar cells Do It Yourself DIY solar panel kit contains 108 string ribbon multi crystalline cells. These newest cells have a little different look from the other cells are still being made in the largest quantity in 's 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 category A cells, though in small number of cells, very 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. 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 kit: (cells, tabbing wires, bus wires, flux, solder)
The standard cell specifications are the following, though the individual cells can be above or below these standards.
Average Power (Watts): 1.75 Wp
Average Current (Amps): 3.5 Imax
Average Voltage (Volts): 0.5 Vmax
Thickness = 200 micron = 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: Tabbing wires: $22 value - 110 feet of tabbing wires that Everbright Solar uses to connect the solar cells. Cut them into 6 inch sections to solder onto the bus bars on the cells. You will get slightly more than 110 feet, but 108 feet is what you need to tab 108 cells.
III: Bus wires: $5.5 value - 11 feet of bus wires. Use them to connect them between the series and connect the tabbing wires ends to the junction box at the back of the panel.
IV: Flux: $7-$9 value - an easy-to-use flux pen that dispenses flux onto the bus bar or your tabbing wires without leaving a mess. It's used to aid soldering and bonding of the wires to the cells. A must have item.
V. Diodes: $4.5 value - 3 diodes rated at 15 amp each. Schottky style diodes.
Some useful information in making solar power:
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.
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 white color 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.
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. If you are inside the building, make sure you shine your sun simulating lamps onto the front of the cell while testing. Place the solar cells on a metal plate, ideally made from copper. With a warm light (ie halogen lights) shining on the cell, put your positive lead from your multimeter on the plate, and the negative lead of your multimeter on the bus bar. Your multimeter will be set to typically check amps or voltage at one time.
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, 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 really can't find a adjustable soldering iron, buy one that's rated at 90 watts.
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. Some people just keep asking question and taking time from us without buying, and we love to give, but please be considerate. Our resources are not limitless.
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, broken cells via transit are relatively rare occurrences, though theoretically it's quite possible. 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, manufactured foam forms, 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 management, but all of our customers have been pleased with the deal they get.
Shipping is free to 48 continent states in the US, if you order $150 or more. We ship the packages via US Postal Service priority mail. Choose Priority Mail shipping method during check out for US Shipping destinations. For international shipping destinations, you must choose Express Mail. For our 175 watt solar panels, choose Ground Freight. We only ship solar panels within United States. 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. We reserve the right to make adjustments to the order if the wrong shipping method and wrote shipping rates were chosen, even if it's our shopping system's fault. We reserve the right to refuse fulfilling orders at any time.
For international orders, we are not responsible for your import duties, customs charges or other VAT's. And we don't know what the charges will be for each country. Do not get upset with us because your government thinks that you should pay extra. In actuality we would prefer to do business all within the United States, but we have some good customers from other countries so that's why we keep our international shipping program. We reserve the right to terminate our international shipping program at any time.
4. Product Returns
We used to have a more strict sounding return policy, but when we looked at the numbers, returns are really so rare we now say that you can return the cells within 7 days broken or not for a complete refund with us paying the return shipping. Almost all of our customers are truly honorable and they didn't abuse our return policy. So far our customers are overwhelmingly happy with the great value and support that we provide.