Project: Get the most from solar panels that are angled differently by wiring

Projects General Guidance
1

What I have is a cube thing with solar panels on the sides, 4 panels total, 1 for each face, each panel contains 6 solar cells, except top and bottom. Each face outputs 6v open circuit 1 amp if I short positive and negative on full sun.

This cube thing will not be outdoors. It will be for instance near a window, kitchen, etc. Direct sun will happen rarely over a month period.

But, whats inside the box thing!?
Inside, I plan to have a powerbank charging itself from the 'thing'.

But, it will take days to charge that battery from solar panels that will probably never get direct sunlight!
Correct, I guess. So my question is what is the BEST way to arrange the solar panels/cells outputs so that I get the most of them?
Please, elaborate on "the BEST way to arrange" them?

Sure. For instance, should I wire all the panels in parallel to get 6v 4A and since it will only get ambient light even 1/4 of amps is good? Or should I wire them all in series to get 24v ish and 1A and add a buck regulator? that way the usb powerbank will at least push some mah to the battery on ambient light?

Trying to find the best setting, I have attached a simple picture to illustrate the above.
Thanks!
EDIT:

You can see on the attachments how each solar cell string is made, each face of the thing is made of 3 solar cell strings, making 6 volts per cell.

Now, on the other attachment, in Fig 1 you can see that the sun hits one face only, making 6v.
But, if you look at Fig 2 the sun is hitting from a different angle, making about ~6v.
How did I came to the ~6v conclusion?
Fig 4. Sun hits from the top left. It hits A1, A2, B2, & B3 panels. A1 and B3 get the direct sunlight, as for A2 and B2 get the sunlight at an angle of 90 degrees, making the cells less efficient. Instead of making 2v like A1 and B3, I estimate they'll make 1v each.

There is 4 "faces" in Fig 1 but, if you include the faces in Fig 2, there will be 8 "faces."
How can I always get 6v regardless of the angle the sunlight is coming from such as Fig 1 vs. Fig 2?

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2

Can you provide some info about the USB Powerbank.
Exactly what is it , and what are its specs.

3

Hi
Sorry your diagram was basically blocks no connections.
Please draw a proper schematic of your connections, in CAD or a picture of a hand drawn circuit in jpg, png or pdf?

When you connect your 6V PV panels, they should all be in parallel.

You should use blocking diodes in series with each PV to prevent any PV that is producing higher output than another from leaking current back through the lower PV cell.

Because a PV panel is a current based device, putting them in series will not help, it will only perform current wise as good as your weakest PV.

Why a cube?
A flat panel hanging in the window will make use of all your PV cells, a cube is wasting your generation power.

Tom.. :slight_smile:

4

I think the best thing is to wire the panels in parallel. However you will probably need to add a diode for each panel to prevent current from back-flowing into a panel that is on the dark side.

AFAIK if you wire them in series the output will be governed by the "darkest" panel.

Best thing of all, of course, is to have all the panels on the bright side. It's rather a waste of money to have panels on the dark side.

It would make a neat Arduino project to mount your cube on a base so the Arduino could rotate it to make the single (?) panel always face the brightest light source.

...R

5

mauried:
Can you provide some info about the USB Powerbank.
Exactly what is it , and what are its specs.

All I know is that it has a capacity of 2000mah 3.7 battery, input is 5.5v @ 1.5A max, output is 5v 1A. I might change this for a more efficient one or a more suitable one.

TomGeorge:
Hi
Sorry your diagram was basically blocks no connections.
Please draw a proper schematic of your connections, in CAD or a picture of a hand drawn circuit in jpg, png or pdf?

Sure!

TomGeorge:
Why a cube?
A flat panel hanging in the window will make use of all your PV cells, a cube is wasting your generation power.

Actually, about that.... Is no longer a cube, see the original post for updates. Thank you!!!!

Robin2:
I think the best thing is to wire the panels in parallel. However you will probably need to add a diode for each panel to prevent current from back-flowing into a panel that is on the dark side.

Best thing of all, of course, is to have all the panels on the bright side. It's rather a waste of money to have panels on the dark side.

This is of the size of a blender, not a "big investment" was made.

6

6 MPPT controllers would do it. I don't know if they would fit inside the cube/object/thingy.

7

MorganS:
6 MPPT controllers would do it. I don't know if they would fit inside the cube/object/thingy.

MPPT's of course!
I cannot find any affordable MPPT's that work below 6v, 6v being the maximum output my panels can provide on full sun, which will occur rarely.
Can you link me into some MPPT's that meet that criteria? Thanks!

8

I can't imagine that you will produce enough electricity to pay for even one MPPT, never mind 6.

...R

9

OK, Ive got a couple of USB power banks which sound similar to the one you are using and they have 18650 cells in them and are designed to run off a USB charging source.
USB charging sources are normally 5V , and 18650 LIPO cells are normally constant current charged at some defined rate.
The issue I see is that the power bank will want 5V supplied to it , and as Solar Panels are current sources which wont supply a fixed voltage, its possible the power bank simply wont work.

10

Hi,
Pringles, sorry but please do not edit original post like that, it has basically disjointed the flow of the thread.
Anyone with a query like yours will not be able to follow the thread as the original post is not relevant to the following answers.

Tom.... :slight_smile:

11

TomGeorge:
Anyone with a query like yours will not be able to follow the thread as the original post is not relevant to the following answers.

Neither can I, and I read and commented on the original.

@Pringles, please reinstate your Original Post to its original state and post your other comments in a new Post following this Post.

...R

12

Robin2:
I can't imagine that you will produce enough electricity to pay for even one MPPT, never mind 6.

...R

This is why I didn't even mention MPPT and went with the best arrangement possible to maximize power and maybe PMW the heck out of it after the arrangement

mauried:
The issue I see is that the power bank will want 5V supplied to it , and as Solar Panels are current sources which wont supply a fixed voltage, its possible the power bank simply wont work.

Setting that aside for a second, lets first discuss what would be the best arrangement for the solar setup.
I hear you that the power bank might not even start because of the dynamic voltage range, but that's another issue. Thanks! also any ideas of perhaps bypass the powerbank? Such as matching the incoming solar power to be battery and monitor voltage to cut of at 4.15v to be safe?

TomGeorge:

Robin2:

Sorry about that, I did not intend to cause this. I'll take your advise, thanks!

13

Pringles:
Setting that aside for a second, lets first discuss what would be the best arrangement for the solar setup.

all panels facing the sun, with tracking.

second best is all panels designed to be full on to the sun during the day. each panel to be slightly angled from the next.

if you cannot have multiple panels, then you would be far better with 1 panel, facing the sun , with tracking.

14

dave-in-nj:
all panels facing the sun, with tracking.

I mention it it a cube shaped thing. How in the world it is possible to make a cube so that each face points at the sun? please don't say mirrors....

dave-in-nj:
second best is all panels designed to be full on to the sun during the day. each panel to be slightly angled from the next.
if you cannot have multiple panels, then you would be far better with 1 panel, facing the sun , with tracking.

This will not be on the roof of a home nor outside. It will be near a few windows.

15

Additional information.
The size of the project is the size of a kitchen blender, for reference.

If you look at the pictures I added, each 'face' (Fig 1) is composed by 3 two volts cells that are connected in series to create a 'face' thus giving 6v. I will be connecting the four 'faces' (Fig 1) in parallel.
That way if the sun it's at 12, 3, 6 or 9 o'clock it will get it's 6v. BUT, what if the sun is coming from 10:30 o'clock? (Fig 2)

Will it only create 2v because it is only having direct contact with the sun on the panels A1 & B3 because they are in parallel? That's the arrangement I need to find so that no matter which direction is positioned, it will make the biggest current.

16

Pringles:
I mention it it a cube shaped thing. How in the world it is possible to make a cube so that each face points at the sun? please don't say mirrors....

That is a silly question.

And the answer is very simple. Just put 1 solar panel on the side facing the sun. Solar panels on the other sides will not pay for themselves.

...R

17

Robin2:
That is a silly question.

I'll make sure I don't post more silly questions.

Robin2:
And the answer is very simple. Just put 1 solar panel on the side facing the sun.

That makes a lot of sense, because the sun is always on the same place, got it!

Robin2:
Solar panels on the other sides will not pay for themselves.

Not trying to live off grid here, not trying to make the solar panels to pay for themselves.

18

Pringles:
not trying to make the solar panels to pay for themselves.

Then why not buy 30 of them. The manufacturers could do with the revenue.

That makes a lot of sense, because the sun is always on the same place, got it!

You have received more than one suggestion to use 1 panel and rotate it to face the sun. You have also received a suggestion "second best is all panels designed to be full on to the sun during the day. each panel to be slightly angled from the next"

...R

19

If you study commercial solar installations, you should rapidly make the observation that for the most part, all the panels are co-planar or in parallel rows, mounted if at all possible at an altitude angle which corresponds to (or is slightly lower than, to increase winter illumination) the local latitude.

They do not put them at slightly different angles, as this will decrease efficiency.

The alternative is of course, to use a heliostat.

20

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