DIY Solar Panel FAQ

 

7. SOLAR ELECTRIC SYSTEM DESIGN (electricity basics, formulas, charge controller, batteries, inverters, etc.)

Q7.1: What are the differences between DIY solar kits and pre-assembled solar panel? Is it strictly a cost issue? It's hard to compare because I feel like I am comparing apples to oranges.

Q7.2: For a 12 volt battery what is the optimum voltage to be running from these panels?

Q7.3: How many amps could I get out of this kit assuming I had the panel at 18 volts?

Q7.4: For untabbed cells, how would a beginner enthusiast solder each cell to comprise a complete panel?

Q7.5: Are these cells for on grid or off grid panels? What are the differences of each?

Q7.6: Case: If I wire in series then my total amps/volts for one panel of 50 solar cells will be 175 amps, and 25 volts. Is this right? If I wire in parallel what would be the difference? Also, so if I do wire in series, I would need a charge controller, and inverter that can handle 25 volts? I'm figuring likely through distance, and such that it will take it down below 25 volts, however what I want is 24 volt system, how can I achieve this? 

Q7.7: How much energy could 3 panels produce in one day.

Q7.8: Do the panels you make still make power if one cell is covered or in shade?

Q7.9: How to set up an off-grid system?

Q7.10: Can you tell me some household item(s) these panels would power?

Q7.11: How do I wire these 3 18v professionally made solar panels together to charge batteries?

Q7.12: Am I correct to say if I need 150W of power, I need to build 150W solar panel? That means I need around 100 solar cells? How many Amp of charge controller should I add into my system?

Q7.13: If I use 3x6 .5v3.6a cells and arrange them into 9 cell string, 4 sets wide, what size wattage panel do I have (72watt, 65watt)?

Q7.14: I just want to know how many cells I would need to buy from you. My house is three phase. Itís running on 100 amps brakers per phase. So I will have to buy solar cells to get 100 amps per phase.

Q7.15: I want to power an 8000btu air conditioner. Whatís the most efficient way to get this job done?

Q7.16: I have a 24 volt system. 150 cells do not seem to have the right multiple. Could I use 152 cells to make 4 series banks and how much more would it be? What is the best glue to fasten them to the glass?

Q7.17: If I hook up 100 of these in one panel I would get a 175W panel but would it be 50v or 25v?

Q7.18: Case: I messaged you last week about my problem with my solar panel and a non charging situation after the second day on a fresh battery. your response was that I add cells to make my panel 18 volts. I did that I made my panel 18 volts and I tested it and my solar panel is now producing 18 volts. I am still having problems with non charging of the battery. After going through my third battery, it is apparent that my solar panel is damaging any battery I connect to it. The battery no longer accepts a charge after the first day I connect the battery to the panel. I dont know why this is happening. If I had a short Im guessing I would not get 18 volts from 36 solar cells but I am recieving 18 volts from 36 cells. Do you have any ideas why my solar panel is damaging any battery I connect to it? Please help I am desperate after working on this problem for over two weeks not.  

 

Back to Main Table of Content

 

 

 

Q7.1: What are the differences between DIY solar kits and pre-assembled solar panel? Is it strictly a cost issue? It's hard to compare because I feel like I am comparing apples to oranges. 

A: Here is a matrix to help you sort out the issues:

DIY pros: Solar education, solar career development, lower cost

DIY cons: Long process, could be frustrating, need to get materials from different sources, quality not as high as ready made panels.

Preassembled Pros: Higher quality, power output guaranteed, not as many hassles, saves time

Preassembled cons: Higher cost, loss of learning opportunity in panel making

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.2: For a 12 volt battery, what is the optimum voltage to be running from these panels?

A: The optimal voltage to be running from these panels is slightly over 12 volts. We recommend our customers to have the panels' voltage to be 1.5 times higher than the voltage of battery. It's also important to get a controller to sit in between your panel and the battery. The function of the controller is to help charge the battery more smoothly, so that the panel doesn't fry the battery when there is too much power, nor drain the battery when there is no or weak sun light. If you really don't want to invest in a charge controller, then you should at least use a diode to your junction box. The diode's function is to make sure that electricity runs in one direction - from the panel to the battery, and not the other way around. The diode will stop the electricity from running from the battery to the panel - meaning draining it.

Bottom line, if the voltage is too low (lower than the battery), then the battery won't charge at all. If it's too high, it will fry the battery. You also have to know the specs of the battery, and what's the optimal time duration of the charge. The other basic concept of voltage is that each solar cell is about half a volt, and if you connect the cells in series (daisy chaining, positive to negative of subsequent cells), then the voltage increases per each cell you add. And for series connections if you build your panels to be between 0.5 volt to 34 volts you should have no problem. If you want to keep increasing the wattage of the panel without increasing voltage, you can choose the parallel connection. The typical layout of your solar cells is that if you have a few sets of cells connected in series, and then connect these sets of series connections into parallel connect. In parallel connection, you connect the positive to positive, and negative to negative. And if you divide the wattage by voltage, you get the amperage.

We are working on a how to manual with diagrams so that our customers can better help themselves. If you have more questions, please send emails to info@EverbrightSolar.com

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.3: How many amps could I get out of this kit assuming I had the panel at 18 volts?

A: The basic and very important formula you need to know is this:

Power (P) = Current (I) Multiply by Voltage, or P=I*V

Power's unit of measure is watts,

Current's unit of measure is amps,

Voltage's unit of measure is volts.

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.

The above is for each cell. For the panel, to get 18 volts, you connect 36 cells in series. And 36 * 1.75 watt = 63 watts. The amps you will be getting is 63 watts divided by 18 volts = 3.5 amps.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.4: For untabbed cells, how would a beginner enthusiast solder each cell to comprise a complete panel?

A: First, you need to understand a very essential concept of a solar cell. A single solar cell is like a full functioning battery, almost exactly the same as your AA battery, in the sense that the front of solar cell is negative, while the back of the cell is positive. The difference here is that regular batteries have chemicals inside that generate current, whereas solar cells need sun light to shine on it to generate current.

Since each cell has negative and positive and individually functioning, you can join them together just like you would for the regular battery in the form of series or parallel connections. You connect cells together by using tabbing wires - the thin flat wires that are the width of the bus bars. You cut these tabbing wires to about 6 inches, two wires for each cell, and then solder all of the tabbing wire on the front of the solar cells on their bus bars, two thick white lines. Then after all of them are done, you solder the wires that stick out from the front side to the back side of the NEXT solar cells, and you repeat this process, daisy chaining them all together. This consecutive negative to positive connection is called a series connection. This increases the voltage of the whole series by 0.5 volt for each additional cell you add. Essentially by doing this,  you can make the series to produce the voltage you need for the battery you want to charge, or the voltage that you need to connect to the grid. Simply having these connected cells is too fragile and you need protection of these cells against moisture and other natural hazards, such as hail and flying rocks in the desert, etc. So you need to seal these connected solar cells really well. Professionally made cells are laminated between two layers of EVA, then on the top solar glass, and at the back, TPT. Then you put an aluminum frame around it. The tabbing wires need to go through the laminate so you can attach your junction box to the wires so that your positive and negative connections can be attached to the devices you want to charge, or your charge controller or inverters.

That's the general concept, but you should take a look at free videos on YouTube by typing in 'how to make a solar panel'.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.5: Are these cells for on grid or off grid panels? What are the differences of each? 

A: These cells can be used for either on grid or off grid panels, although it's probably wise to use professionally made panels for on-grid applications. You should gain experience by making smaller wattage panels and then move up. You can always connect many smaller successful panels to get to the higher wattage that you need. And your chance of success is higher by starting out with making off grid, smaller panels. It's recommended that you make panels 100 watts or smaller.

These cells are full size cells that Evergreen solar uses on their big panels. In the future we will be offering cells that are cut from this full size panels into smaller ones so that people can make lower wattage, high voltage panels.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.6: Case: If I wire in series then my total amps/volts for one panel of 50 solar cells will be 175 amps, and 25 volts. Is this right? If I wire in parallel what would be the difference? Also, so if I do wire in series, I would need a charge controller, and inverter that can handle 25 volts? I'm figuring likely through distance, and such that it will take it down below 25 volts, however what I want is 24 volt system, how can I achieve this? 

A: If you wire all 50, the voltage will be around 25 volts, that's correct. Let's say the cell that has the lowest power in your series is only 1.4 watts each, then your total wattage in your series is 50*1.4 watts = 70 watts. The amps will be 70 / 25 = 2.8 amps. If you connect in parallel, voltage will NOT increase per each cell, but stays at 0.5 volt, which is not very useful for almost any applications. Parallel connection is more useful when you have two independent series that already have their voltage increased.

I can tell you that in most situations, solar cells will be connected in series, and the most common configuration is 36, 72 cells series. In you want still higher power for your panel with these Evergreen cells, then parallel two 72 cell series on your panel.

In almost all situations, you want your panels to work with a charge controller (for batteries), or an inverter (for power grids). The voltage of your panel should be 1.5 times the voltage of your charge controller's rated voltage. So your 36 and 72 cell panels will work with almost all charge controllers, which come in 12 or 24 volts. In short, stick to 36 or 72 cell configuration, you can't go wrong. What do you with the extra cells? Prepare for breakage during panel making process, and you can keep adding on to your panels stockpile as you gain experience.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.7: How much energy could 3 panels produce in one day.

A: Here is my general guesstimate:

Assuming you have 72 cells, and since you are going to lose a some sun light conversation efficiency after your cells are put in a panel (inefficiency cell stringing and low power cell wastage, glass, poor soldering, EVA encapsulation efficiency loss etc.), your 72 cell panels produces about 100 watts each. 3 panels are rated you 300 watts. And if you have 6 hours of sun light, that gives you 1800 watt hours, which is 1.8 KWH. Does it make sense to you?

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.8: Do the panels you make still make power if one cell is covered or in shade?  

A: If one cell is covered in shade, your panel will still produce power, but at a much lower rate. Perhaps over 70% or more power is gone. To minimize power loss, most professionally made big panels (72-cell panels) have three, four, five or perhaps six bypass diodes inside the junction boxes at the back of the panels. These diodes are bypass diodes that will by pass the string segment in which the cell that has been covered or in shade, and allow the other segments to continue to produce their maximum power. With in the system where multiple panels are put together in an array, you can use a newly developed product that will soon be released to the market to minimize shading loss of the whole array when only portions of the panels are in shade.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.9: How to set up an off-grid system?

A: Your off grid system should be set up this way:

Solar Panels ---> Charge Controller ---> Batteries ---> Inverter (Stand alone type) ---> AC appliances and other power consumers.
18 or 36 volts       18v,36v -->12v, 24v    12v, 24v                    12v, 24v ---> 110v

From left (input) to the right (output).

Your inverter does not interface (connect) with the panels directly. It takes input from the batteries via the charge controller. And that's why your inverters take 12VDC input for the most part.

Your panels should be >18v or > 24v to charge your 12v or 24v batteries. Panel output voltage is typically 1.5 times the input voltage of a battery.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.10: Can you tell me some household item(s) these panels would power?

A: This set of 100 cells are individual, fragile cells that you need to solder together using the tabbing wires we provide and make them into solar panels to be useful. You can use series or parallel connections to get the desire voltage of your solar panel, and then the panel can charge your 12 volt or 24 volt batteries. Solar panels and batteries put out direct current, which are good for some laptops, heaters and motors but your other household appliances will require AC current, which means that you will need an inverter to convert DC power to AC power for them.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.11: How do I wire these 3 18v professionally made solar panels together to charge batteries?

A: There are connector cables that you can buy to connect to your junction boxes on your solar panel. And there are Y shape connectors that you can use to connect negative to positive terminals.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.12: Am I correct to say if I need 150W of power, I need to build 150W solar panel? That means I need around 100 solar cells? How many Amp of charge controller should I add into my system?

A: You are more or less correct. In your example, 150 is a rating, and for the panel that is 150 watts, it means that under standard testing condition, under full sun, the panel can generate 150 watts. But that also means that you are always going to need full sun to get that much power - over time. But in reality that's not the case, however it doesn't really matter. Depending on whether you are buying the latest cells (multicrystalline look Evergreen cells), then a 72 cell panel will give you around 100 watts. But then you  think of the voltage output of your panel, and if you build 36 or 72 cell panels you will have 18+ and 24+ volts output, which works well with most charge controllers. If your cells are connected in series, then your panel output using our cells will be around 3.5 amps, which is good for most of the smaller charge controllers.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.13: If I use 3x6 .5v3.6a cells and arrange them into 9 cell string, 4 sets wide, what size wattage panel do I have (72watt, 65watt)?

A: Assuming each cells generates 1.75 watts, then connecting them all in series will give you 36*1.75=63 watts. The total wattage will be the multiple of the lowest power cell. Panel level wattage will be lower because of the power loss from solar glass, poor soldering, improper use of wires, etc.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.14: I just want to know how many cells I would need to buy from you. My house is three phase. Itís running on 100 amps brakers per phase. So I will have to buy solar cells to get 100 amps per phase.

A: Making panels yourself to power the entire house is not a trivial thing. It's best to consult a qualified electrician. It's safer that way. We only recommend that people make smaller panels for off grid applications that are lower voltage, though many of our buyers are electricians themselves and they know what they are doing when they make big panels from our cells.

Most American homes need 3000 to 8000 watt solar panels systems.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.15: I want to power an 8000btu air conditioner. Whatís the most efficient way to get this job done?

A: The most efficiency and realistic way to do this is still installing several thousand watts system and feed your electricity through an inverter to the grid and for your conditioner to draw power from the grid, because that's the only reliable and realistic way to power your conditioner continuously. Your solar electric system will balance the power you send to the grid and the power you draw from the grid, if you have net metering system in your local area.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.16: I have a 24 volt system. 150 cells do not seem to have the right multiple. Could I use 152 cells to make 4 series banks and how much more would it be? What is the best glue to fasten them to the glass? 

A: Make 72 cells to get around 36 volts. You need 1.5 times the voltage from your panel than your 24 volt battery system. This is to take into account of the lower voltage during different hours of the day, the resistance in the wire between your panel and the battery, and the diodes in your charge controller.

You can make two 72 cell panels, each giving you 36 volts to power your system.

The solution to glue your cell to the glass is to use a small drop of silicone. Use a small amount so that your glass expansion rate under heat will not affect the silicon cell expansion rate.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.17: If I hook up 100 of these in one panel I would get a 175W panel but would it be 50v or 25v?

A: If you connect them all in series, then it will be 50 volts. If you connect 50 cells in series, and then repeat it again for another series, you will have two 25 volt series. You can then either parallel connects the two strings to get 25 volts, or series connect these two series further to get 50 volts.

Back to Main Table of Content

Back to Solar Electric System Design FAQ

 

Q7.18Case: I messaged you last week about my problem with my solar panel and a non charging situation after the second day on a fresh battery. your response was that I add cells to make my panel 18 volts. I did that I made my panel 18 volts and I tested it and my solar panel is now producing 18 volts. I am still having problems with non charging of the battery. After going through my third battery, it is apparent that my solar panel is damaging any battery I connect to it. The battery no longer accepts a charge after the first day I connect the battery to the panel. I dont know why this is happening. If I had a short Im guessing I would not get 18 volts from 36 solar cells but I am recieving 18 volts from 36 cells. Do you have any ideas why my solar panel is damaging any battery I connect to it? Please help I am desperate after working on this problem for over two weeks not.  

A: You should always use a charge controller when charing a battery. How large is your battery? Is it a car battery? How do you measure the voltage and amps of your battery? When you measure your battery's power and amperage, make sure that you don't don't create a short curcuit so that your multimeter's fuse is burned. Connect a load to your battery, and series connect your meter to the load. I am suspecting that you meter is broken, not the battery. Tell us if that's the case. 

Back to Main Table of Content

Back to Solar Electric System Design FAQ


 

 

 


Home Page    |    Products    |    Services    |    Contact Us    |    DIY FAQ    |    Events / News
Copyright © 2008-Everbright Solar, inc.All Rights Reserved.