Transporting Solar Cells

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.

Charge Voltage etc.

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.

Solar Polarity

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.

Solar panel Math

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.

Understanding solar Energy and Panels

My new Projects consist of the fallowing material.
Cells:

The standard cell specifications are the following, though the individual cells can be above or below these standards.

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 inches x 3 inches,
Weight: Just above 6 grams, or 0.2 oz.

Tabbing wires: $22 value - 110 feet of tabbing wires that Evergreen 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.


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.

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.

Solder: $7-$9 value - a tube of solder to help you solder the tabbing wires and the bus wires together, or whenever you need extra solder.

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