# i am trying hook up my solar set up and i got it working but need pointers on a way to make it better?

Hi i hope someone can help me with this im not totally new to electronics but some things still kind of not sure about, that being said i bought three 4.5V/90mA (mine avg 3.2V in direct sun) solar cells and a http://www.bgmicro.com/SS1203A.aspx and i know how to hook it, up but what im wondering is if i bought 3 more of the 4.5V/90mA cells could i hook 2 sets of 3 cells kind of of like this
--[ + - ]--[ + - ]--[ + - ]--
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and tie each set together and hook them in the controller am i right in thinking that the volts would not go up but the amps would, and also if anyone could give me an example on the math how i would figure out the mA of the cells all hooked up this way if it would work. the math parts the biggest prob i have with all the electronics ( should have paid more attention in school lol )
Thank you in advance for any help
William

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6 years ago
I think your intuition about series and parallel circuits is pretty much correct.  Just like with chemical batteries, you can get more voltage by stacking cells in series.  And you can get more current by putting cells together in parallel.

In a series circuit each element shares the same current, and the voltage across the whole stack is the sum of each individual voltage rise (or drop).

In a parallel circuit each element shares the same voltage, and the current that flows into, and out of,  the whole array of them is the sum of the currents sourced (or sunk) by each individual.

For your solar cells its usually safe to assume each one is identical in terms of the voltage or current it supplies.  For a series stack, you assume each cell has the same voltage.  So that three cells in a series gives 3x the voltage, and 1x the current of just one cell.  For three cells in parallel, you get 3x the current, and 1x the voltage of just one individual cell.

The same logic applies to battery cells, wired in series, or in parallel.

By the way, the actual current and voltage supplied by a solar cell depends on what you are loading it with.  Also I should point out one of the ugly truths of the solar cell marketing, which is the numbers they quote for voltage and current are usually the open-circuit-voltage (the voltage while supplying zero current) , and the short-circuit-current (the current when shorted, i.e. supplying zero voltage).  There is no way to get the solar cell to supply both that much current and voltage at the same time.

Also regarding the charge controller, for what size battery is it intended?  What battery do you want to charge with it?  I am guessing that charge controller is for a 12 volt lead-acid battery, but that's just a guess.  Strangely the product link you gave to bgmicro.com did not say.

I am guessing that you'll want a stack of maybe 5 or 6 of those cells in series, just to give the charge controller enough voltage to work with, if it is a charge controller for a 12 V battery.

BTW, the mathematical basis for voltages in series adding, and currents in parallel adding, is just Kirchoff's laws
http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws

And this notion of loading,  i.e. the cell voltage dropping as you draw more current from it, you can model that with something called a Thevenin equivalent circuit, a model consisting of just a voltage source in series with a resistor.  The following wiki article does an ok job of explaining loading.

6 years ago
+1
Don't forget at night the solar cell is just a resistor and will discharge your battery.
A single schottky diode is used to prevent discharging by night if you are to
busy to do it yourself.

A
World of warcraft junkie (author)  iceng6 years ago
oh ok cool thank you, i didn't know that the solar cells would drain the battery, i just thought when sun went down no more power would come in, i wonder if with my controller if i need that diode or if its got something like that built in to it?
6 years ago
I would bet any controller has a built in reverse discharge diode.

A
World of warcraft junkie (author)  iceng6 years ago
thank you again for the help, i did open the controller up and it does have a diode in it soldered so i cant read the numbers but there is one lol
6 years ago
+1
Taking things apart is half my knowledge base.
6 years ago
Yeah the bgmicro link did not tell me much about it either and i thought well im still learning so i would buy cheap for now. but about the part where you was talking about battery's in series, or in parallel, i learned about when making the mint tin amp by kipkay on here, i tweaked his and added 2 9v battery's and still haven't had to change battery's lol, (sorry getting off topic) that's why i was kind of wondering if solar cells work in the same way.

the controller is for 12V battery not sure if i matters if its lead acid or one like the sealed gel battery's like in the apc computer's thing's, but i have both i can play with, ( also i included a pic of the controller its the only stats on it ).
( not sure if the pic will be big enough to read so specs on it are
Product Model: SS1203A
Product Serial Number: 100901092
Input    | Voltage: 12V | Current: 3A | Power: 36W
Output | Voltage: 12V | Current: 3A | Power: 36W
not sure if that helps but i know giving all info i can should help some lol)

but i was hoping to get this set up so i can power my custom shop lights im making there led lights and got a led spot light on the out side my shop and shining at my back door of my house all running off my 12v car battery, i live kind of in the sticks so extra lights nice lol.

also i have it set up where i can charge mine and my wife's cell phone's when we loose power happens a lot lol out here, and can go for days with out power company getting lights back on so its nice to have our Droids working at least.
6 years ago
included a picture i made with my schematic program so i can get how i'm wanting to hook them up better so that way there's no miss understandings lol, and thanks again for the help guys its cool theres people still around that will help someone out.
Jack A Lopez6 years ago
I found a little bit more data on that charge controller.  It looks like it's made by Sinasolar of Zhejiang province.  Here:
http://www.sinasolar.com/solar-charge-controller-SS1203.html
and here:
http://sinasolar.en.alibaba.com/product/452138119-210327450/Solar_Controller.html

Still a little bit cryptic, but I am going to guess at the intended application for this charge controller, and some of the assumptions that went into its design.  Mostly this is just building on what I was guessing before, that this is a charge controller intended for charging a 12 volt lead-acid battery,  from a 12 volt photovoltaic module, aka solar panel.  Guessing that is why this charge controller is labeled the way it is.

Ah, but what is a 12 volt PV module?  Is that some kind of popular/standard thing?  Is the voltage output by a 12 volt PV module exactly 12 volts?  The answers to those last two questions are yes and no, respectively.  A nominally 12 volt PV module is indeed a  popular/standard thing, and the open circuit voltage of such a module is about 20 volts.  (See the attached picture for a typical I-V curves.)

BTW, that word "module" is, I think, meant to refer to collection of individual "solar cells" wired together (in some arrangement of series and parallel) and sealed into a weatherproof package, and sold, and finding its end with the individual cells wired that way as a module.

Anyway, what I'm saying is that the thoughtful Chinese engineers who designed that charge controller, sort of assumed that you would be using one of these "standard" 12 volt PV modules, rather than some funny homebrew setup made from individual cells wired together.

Not that I have anything against homemade PV modules,
https://www.instructables.com/id/How-to-MAKE-PV-Solar-Panels/
but  if  you are going to do things that way, then I think the trick is to make your homemade module so that, electrically, it is similar to the module the charge controller was expecting.  And what it's expecting is an I-V characteristic similar to the one in the attached picture.

Well, similar to the picture, but with the current scaled to your charge controller, i.e. max current less than 3 amperes.

Anyway, that's why yesterday I was suggesting a stack of like 5 or 6 of your cells, an arrangement to give an open-circuit-voltage of around 20 volts, the same as you'd get from a standard 12 volt PV module.

Hope that's not too confusing.

Also,I know I said I didn't have anything against building your own modules, but... the only reservation I have is that building modules is tedious, hard work.   Anyway I said there really was such a thing as a standard PV module, so I should probably point to some examples of those.
Arizona Wind and Sun - Modules from 1 to 100W
http://www.solar-electric.com/1to39wasopa.html
Similar Modules at the Alt-E
http://www.altestore.com/store/Solar-Panels/c541/page/1/sort/4a/
Also the link from where I borrowed that I-V curve:
http://www.altestore.com/howto/Solar-Electric-Power/Design-Components/Electrical-Characteristics-of-Solar-Panels-PV-Modules/a87/

Jack A Lopez6 years ago
If you can find some documentation for that charge controller, therein might be answers to what kind of solar PV module it is expecting to power it.  It might not have come with any documents since you bought it surplus, but there may be some markings on it which reveal who made it, and clues to where you can find more info about it.