Understanding Solar panel data

[Tenor]

I have a source for free solar panels and I would like help in understanding their output.  Here is what the 2 I have say:

Max Power 50W
Max Systen CKT Voltage 600W

Current:
Short CKT 3.35A Rated 3.15A
Open CKT 19.8V Rated 15.9V

Bypass Diode - Installation Guide 019831

There are 2 boxes for wiring on each unit.  One is marked Pos.  Each box has 2 terminals and there is a diode between each.  Today I am getting 18.99v DC in the sun on one positive contact and 6.73(approx) from the other positive contact.  These panels are Seimans Model SM 50-H and are 48x13x1 3/8"

[boogiethecat]

Not sure exactly what you want to know.   

What it's telling you is that in full sun you'll be able to get 15.9 volts at 3.15 amps, or 50 watts, out of each panel.  To interface it to a 12 volt battery system you'll need a solar controller for each panel or a bigger controller if you want to hook all the panels together, they are cheap (ebay) and their electronics will convert whatever the solar panel puts out to the proper voltage to charge and maintain your 12 volt batteries.

The bypass diodes are used when you hook more than one panel together...

I would ignore the 6.73 volt terminals, don't know what they are for and probably not applicable in your case

Can you get more of these? I'd love 3 or 4 for my bus... (seriously)

Cheers
Gary

[Tenor]

Boogiethecat,
I don't understand the difference between "Open CKT (circuit?) 19.8Volts" and "Rated 15.9Volts".  As I put my multi meter on it, I get 18.99 VDC.  What does "Open CKT" mean?  Is the "Rated" number just an average expected output?  Also, to help look for a proper controller, which current numbers should I go by, "Short CKT(circuit?) 3.35 Amps" or  "Rated 3.15 Amps"?  Thanks!

[buddydawg]

open-circuit voltage (Voc)--The maximum possible voltage across a photovoltaic cell or module; the voltage across the cell in sunlight when no current is flowing.

short-circuit current (Isc)--The current flowing freely from a photovoltaic cell through an external circuit that has no load or resistance; the maximum current possible.

Get a controller with an input rating of 16-20 volts and and amp rating to cover the number of cells to be used.

[Don Fairchild]

I would also like about 6 of those panels. gary and I could have them shipped together or depending where they are I could come and get them.

Don
888-473-3626

[Tenor]

Get a controller with an input rating of 16-20 volts and and amp rating to cover the number of cells to be used.
Posted on: Today at 03:02:06 PM Posted by: Tenor  

That's the most valuable piece of info I needed.  Thanks Buddydawg!  
Gary, I have access to these on a first come first serve basis.  They are damaged takeoff's from a company that makes solar road construction signs.  These first two have shattered safety glass that the cells are laminated to.  It doesn't seem to affect output, but they will need to be modified.  They are mounted in aluminum frames.  I plan on attaching Plexiglas over the outside and perhaps use Styrofoam to support the backside.

I'll keep the board posted about availability.

Just realized another question,
My house batteries and inverter are 24 volt using a Vanner equalizer to supply 12 volts.  Should I wire these panels in series and use a controller to keep them outputting 24 volts?

[boogiethecat]

Hi Tenor,
As Buddy stated, the "open circuit" rating is simply what the panels can put out with no load connected.

If you're going to use them with a 24 volt house system, you'll need to connect two panels in series and find a 24 volt controller.

One thing on the broken glass- the glass that they put over solar cells is a special glass that is optimized by reduction of iron content in the glass formula, and it is also antireflective coated, so that it transmits the wavelengths of light that solar cells like, a lot better than regular glass.   If you put regular glass or plexiglass over your cells, you will find that the array will put out a lot less than rated power.  To do it right you'd have to use the specialty glass.
  If you don't really care, it's not a big deal, but using plex or regular glass over the cells can easily turn a 50 watt panel into a 35 watt panel !

[Tenor]

Boogiethecat,
Is there a better way protect these?  The glass is completly shattered. 

Sorry Boggiethecat, tire eyes missed your line about using the special glass.  I'll probably do plexi and accept the loss.  I would guess the other option would be pretty expensive.

[ol713]

Hi;
   I also have a 24vdc inverter with a Vanner for the 12vdc system.
   The solar panels also hooked in series for 24vdc.  It keeps house
   batteries charged and the charge rate is enough to trigger the
   Vanner to keep the 12vdc charged also.  Also, my solar controller
   has a battery switch for two battery banks.  I wired mine to charge
   house battery or start battery.  Comes in handy when start battery
   is low.
                                 Good luck,   Merle.

[Tenor]

Merle,
Can you tell me what make and model solar controller you are using?  Is it ok for low temps?