Issue With Panel Voltage

[SunHarvester]

Hi there, so I'm in the process of creating a solar panel, and I've encountered an issue that I'm hoping you all might be able to help me solve. When measuring the voltage of the panel as a whole in full sun, I get a voltage reading of roughly 6 V. Now, I have a 36-cell panel, with each cell measuring about 0.5 V, so ideally, my panel should read 18 V. I've gone and measured each individual 12-cell column, and every one also reads roughly 6 V. So I'm assuming the problem is that I've incorrectly wired the columns in parallel, but I thought I correctly wired them in series. I've attached a picture for everyone's perusal, and if anyone can point out what I've done incorrectly, it would be much appreciated. Thanks a lot.

[Sunking]

Now, I have a 36-cell panel, with each cell measuring about 0.5 V, so ideally, my panel should read 18 V. I've gone and measured each individual 12-cell column, and every one also reads roughly 6 V. So I'm assuming the problem is that I've incorrectly wired the columns in parallel

My best guess is by your description and clues given, it is most likely a wiring problem, or a YES to the question.

First clue is you say you measure 6 volts in each of the 3 rows. All read 6-volts. Based on that one has to conclude all 3 Rows are wired in parallel making your panel 12S3P. If they were in series, the voltage would add up to 18 volts.

Unfortunately your picture does not tell us much. Looking at the wiring Busses at the Top and Bottom of the panel where you think you wired them in series look OK. But what we cannot see is Polarity.

Start with this simple check. Make sure every positive terminal is connected to a negative terminal of every cell. That will verify if the cells are wired in series. If you see any terminal connected Positive to Positive, or Negative to Negative you have a wiring issue as that is Parallel.

So back to my guess which is you did not flip over one of the 12 cell rows during final assemble In fact a great guess or what might appear as Magic is you did not Flip the Center Row. I even bet you did not flip the Center Row. If you did that would put all 3 rows in parallel. Just look at either end of the panel where you wired the Busses and check which Polarity at either end. I bet you find all Positive terminals at the same end.

It would explain why you see 6 volts on assembled panel. At either end, the polarities alternate. Example say on 1 end you should see Positive-Negative-Positive, on the other end is reversed Negative-Positive-Negative.. It must be in that order.

Just remember the only connections you should see is Positive to Negative. No Positive to Positive or Negative to Negative connections. The only place there is no connections are the positive terminal on the first cell, and the Negative on the last cell. Those two are your Outputs.

[SunHarvester]

Start with this simple check. Make sure every positive terminal is connected to a negative terminal of every cell.

Thanks for your response, and I apologize in advance for my late reply. Do I perform this check simply by seeing that the tabbing wire goes from the top side of one solar cell to the bottom side of another, and not from top side to top side, or bottom side to bottom side?

Just look at either end of the panel where you wired the Busses and check which Polarity at either end. I bet you find all Positive terminals at the same end.

How do I go about checking polarity at one end? Thanks for all the help.

[inetdog]

Thanks for your response, and I apologize in advance for my late reply. Do I perform this check simply by seeing that the tabbing wire goes from the top side of one solar cell to the bottom side of another, and not from top side to top side, or bottom side to bottom side?



How do I go about checking polarity at one end? Thanks for all the help.

Just like you check the voltage of batteries in series. You start at one end of the stack (say the negative end), then keep the negative probe there are you move the positive probe from point to point along the stack.

If you measure 6V to the top of the first stack and 6V to the top of the second stack, you have probably connected the plus of the first stack to the plus of the second stack. Then the minus of the second stack to the minus of the third stack and you will measure 0V at the negative end of the second stack and 6V again at the positive end of the third stack.
This differs from putting them in parallel because you still have them in a single series string, you just have one "battery" in backwards.

If you lined up all the cells with the bottom tabbing wire at the same end of the panel, you will have to run a bus wire from the top of the first stack to the bottom of the second stack to get them properly in series.

[SunHarvester]

Okay, I see. So you guys are saying that the orientation of each column/stack is important for the wiring due to the column's polarity. This I was unaware of. So that, then, leads to a new question: What judges the polarity of a column/stack of solar panels? In other words, is there any rhyme or reason regarding which end of the column is positive, and which end of the column is negative? Or is it just completely arbitrary, and the only way to test polarity is with a multimeter? Again, thanks for all the help.

[bcroe]

The face of the cell is one polarity; the back is the other. You connect them in series face to back,
face to back, etc all the way through. I think you broke that rule between columns, so 2 columns
are bucking each other. Bruce Roe

[SunHarvester]

I understand that for a singular cell, there is a positive (back) side and a negative (front) side. However, for an entire column of solar cells, I can see using a multimeter that there is both a positive end and a negative end on the upwards-facing side. So I am curious as to whether this polarity for the entire column is arbitrary or if there is some rhyme or reason to it.

[bcroe]

The column is just a collection of cells; the cells still determine polarity. Bruce Roe

[SunHarvester]

The column itself has polarity. When I use a multimeter on the terminals (located on the intersection of tabbing wire and bus wire) of a particular column, it is clear that there is a positive and negative terminal on the column. I don't understand what, if anything, determines which terminal is positive and which terminal is negative.

[littleharbor]

The column itself has polarity. When I use a multimeter on the terminals (located on the intersection of tabbing wire and bus wire) of a particular column, it is clear that there is a positive and negative terminal on the column. I don't understand what, if anything, determines which terminal is positive and which terminal is negative.

Are you sure about this? The buss tabbing you are soldering the positive tab wire to would obviously be negative as it is still a series connection. It is just carrying the current over to the next inverted column of cells.

[bcroe]

The column is just a collection of cells; the cells still determine polarity. Bruce Roe

This is still the answer. The sum of the voltages around a loop are zero; you need more lab experience. Bruce Roe

[SunHarvester]

When I use a multimeter on a column of solar cells, I put the positive lead on one terminal, and the negative lead on the other terminal. The reading is approximately 6 V. When I swap the leads, the reading is now approximately -6 V. What is the explanation behind that? Also, if there is no polarity on the columns, what was Sunking referring to when he directed me to "check which polarity on either end"? Thanks for the help.

[Mike90250]

The polarity is determined by how you wire the Front side (-)to the Backside (+) See attached pic. The sunlit side is minus, the backside is +
Each cell produces about half a volt, 12 cells should give you 6v, which is NOT enough to recharge a 6v battery.

PV cell Function.png

[SunHarvester]

Mike90250, your post was the catalyst for my Eureka moment. I see the error in my thinking, and now I get it. Thanks for all the help, everyone!

[Mike90250]

a picture is worth a thousand words. Glad to be able to help.