Wattage of solar panel

Hi all, I purchased a s/hand C/van which has a large solar panel fitted on the roof. There is no paperwork or markings to indicate the size (wattage) The panel is large measuring 700mm across X 1340 in length. Would anyone have a similar size & if so could tell me the wattage of it please. Rather than unbolt it I thought asking a question would be the easiest. Thanks Rob
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Reply By: Racey - Friday, Jan 20, 2012 at 10:25

Friday, Jan 20, 2012 at 10:25
Hi, I have a similar size which is 120w.

Cheers
Racey
AnswerID: 475476

Reply By: The Bantam - Friday, Jan 20, 2012 at 10:33

Friday, Jan 20, 2012 at 10:33
Ya realy cant rely on size, over the years solar panels have got very much more efficient and a hell of a lot more powerfull for their size.

When I first started taking an interest in solar back in the early eighties ya decent standard 4 foot by 2 foot ish panel was a nominal 6 watts, these days a panel arround the same size & quality is nominaly arround 80 watts.

If it was a recent modern pannel your panel would be arround the 120 watts, but if it is a few years old it could be as low as 60watts.

cheers

AnswerID: 475477

Reply By: Lucko - Friday, Jan 20, 2012 at 11:03

Friday, Jan 20, 2012 at 11:03
I agree with Racey, ours is around that size - 130Watt.

Mark
AnswerID: 475482

Reply By: Battery Value Pty Ltd - Friday, Jan 20, 2012 at 11:29

Friday, Jan 20, 2012 at 11:29
You could measure it.

Select 20ADC on your multimeter and measure the current coming out of the panel.
Then, measure the voltage. If voltage shows around 20V, multiply the current reading by 17.5V (max power point voltage of a typical 12V panel) which gives you the wattage.
If voltage reads around 40V, multiply the current by 35V.
Needless to say, you need the panel pointing to a full sun for this test.

cheers, Peter
AnswerID: 475483

Follow Up By: Member - John and Val - Friday, Jan 20, 2012 at 21:09

Friday, Jan 20, 2012 at 21:09
NTVRX,

I agree with Peter. Measuring is probably the only way to get a good answer....BUT..... disconnect the battery from the panel before you connect your current meter. Otherwise, depending on where the controller is mounted it's possible that the battery could discharge through your meter and let all the smoke out of it!

Cheers

John
J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein

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FollowupID: 750471

Reply By: member - mazcan - Friday, Jan 20, 2012 at 11:46

Friday, Jan 20, 2012 at 11:46
hi
how close to the roof is it can you slide a mirrow under the edge and see anything shinning a torch on the mirrow to reflect the light ?????
AnswerID: 475484

Reply By: NTVRX - Friday, Jan 20, 2012 at 19:10

Friday, Jan 20, 2012 at 19:10
Thanks everyone for the replies. Robert
AnswerID: 475528

Reply By: drowned_rat - Sunday, Jan 22, 2012 at 09:13

Sunday, Jan 22, 2012 at 09:13
There isn't a great deal of difference in efficinecy these days (maybe 10%) except if the panel is an amorphous panel ( thin film), in this case the output will be approx half that of a panel with the individual solar cels on it.

This site shows a good picture of the difference between the two:
Thin film vs individual cells.

AnswerID: 475649

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