Solar cell Basics

[Deepsouthzack]

I am somewhat new to Pv cells and see many concerns posted about the construction of these home built seconds from ebay.

Personally I have no idea what I can get away with so I will post some of my observations and those with more experience and knowledge can please correct me where needed

Heat, when soldering what can happen from to much heat?

So far I have had the best results using 63/37 and a 40w iron for soldering the pads and the leads with the leads being some what hit or miss.

2% & 4% silver show promise for the leads but as of yet I can not seem to determine the technique for a good bond.

When I can get 4% silver to bond to both lead and cell it can not be pulled loose with out destruction of the cell. But I can not seem to get consistent results using anything on the leads.

The back pads have not been a problem.

As far as I know I have not caused any damage to a cell from to much heat.

How will I know if I have?

What can moisture do to a cell.

I assume it corrodes the traces in the cell, is this correct?

The construction of the cells seems to indicate they can tolerate some fracturing of the cell and still produce rated output but makes them difficult to handle.

The biggest problem I have noticed on these cells is that many of the leads are poorly adhered from the start and will pull loose of the cell, all of the other defects seem to not effect rated output to any great measure. Aside from missing large areas of the cell.

All cells need to be checked for output before assembling due to placing a bad cell in a circuit will lower the total output of the panel.

Now if I could only come up with a casing I am happy with & will not cost as much as a factory panel.

I am currently leaning towards a solar room with the panels assembled on a plywood backing.

It has been the only cost effective means of protecting the panels I can come up with so far.

[troy]

I've never worked with loose cells, so can't make any comment on technique.  But your solar room sounds interesting.  Keep in mind that assembled panels can't tolerate shade over even one cell, which kills the output of the entire panel.  So however you arrange your room, it can't cast any shadows on even parts of panels.

Good luck and have fun!

troy

[juiced]

This is a problem i am experiancing myself.

   im not sure if i understand how it works. I think, the cell tries to output your collected energy when it is dark; ie. the reason for blocking diodes.

    If not, it cuts the circut?

  Please clear us up on this.

[troy]

Solar cells are made of doped semiconducting silicon.  When exposed to light, they conduct pretty well, and also due to the photoelectric effect, actually produce the electrons to conduct.

However, when they are not brightly illuminated, they don't conduct well and since the cells are generally wired in series, it blocks the output of the whole string.  This is a somewhat simplified explanation, but you get the idea.

Good luck and have fun!

troy