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Old 25-05-2015, 14:42   #76
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Re: Solar Panel efficiency - Should I upgrade

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Originally Posted by mitiempo View Post
You might get 2 or 3 amps more with MPPT.

If you have the space get the extra panel. If you have the budget add MPPT later to maximize the array.
eventually I would like to add 200 watts more. By using 100 watt panels I have more flexibility in mounting them but that lil mppt won't handle 400 watts so would need two of them or a bigger unit. At a signifantly higher price.
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Old 25-05-2015, 14:50   #77
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Re: Solar Panel efficiency - Should I upgrade

The SunPower cells I have actual tested myself do not have 'built-in' diodes. The video claimed it was the 'connections'. This is sales and marketing bs, frankly I would question all of the reported data.

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I think you are on to something: look at the Vmp for a Sunpower X-series SPR-X21-255 panel: 42.8V. Looks to me as all cells are connected in series, traditionally worst case for shading resistance.

Then I found this tidbit @ http://www.energyplussolar.com/s/Pro...iency-ocir.pdf


Now, just where can I buy a couple SPR-X21-255 in the US

Dirk
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Old 25-05-2015, 18:57   #78
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Re: Solar Panel efficiency - Should I upgrade

So Jack, you have tested Sunpower cells (C-series? or X-series?), have you tested panels?
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Old 26-05-2015, 10:47   #79
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Re: Solar Panel efficiency - Should I upgrade

I have not tested the panels, they very well may have bypass diodes added, it just isn't 'built-in' to a CELL.
I have asked in one thread if anyone has the X panels and did not get any replies. If they are not sold retail, hard to even get a price for them.

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So Jack, you have tested Sunpower cells (C-series? or X-series?), have you tested panels?
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Old 26-05-2015, 12:36   #80
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Re: Solar Panel efficiency - Should I upgrade

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Here's one for ya right now with overcast skys I'm seeing almost 8 amps out of my 200 watts ( side note the panels are windy nation made with sun pro mono cells)
Weather | Personal Weather Station: MTCNW1 by Wunderground.com | Weather Underground this station is less than a mile from the boat and showing a UV index of 3
Yes, cloudy days can still produce a surprising amount of power.

There is also a refraction effect caused by the edges of moving clouds. This quote is from a solar installer site.

Quote:
If you have solar panels and keep a close watch on your power output, you may have noticed a strange phenomenon: on a partly cloudy day, it’s possible to exceed your solar system’s power rating and produce more power that you could on a sunny day. Known as the “edge of cloud” effect, this happens when the sun passes over the outer edge of a cloud, magnifying the sunlight. The intense light causes your solar system to boost power output temporarily, which can help balance out losses from full cloud cover. Solar installers typically select system components that can handle temporary power boosts of this nature (similar effects can occur when sunlight is reflected off snow or water).
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Old 26-05-2015, 12:42   #81
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Re: Solar Panel efficiency - Should I upgrade

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The SunPower cells I have actual tested myself do not have 'built-in' diodes. The video claimed it was the 'connections'. This is sales and marketing bs, frankly I would question all of the reported data.
I don't see how they have anything to gain by lying. There are people out there like us who are curious enough to check these kinds of claims, so I don't see how they think they can get away with something so easy to verify.

You could start a thread asking if anyone who owns Sunpower panels could experiment with different sized pieces of paper shading their panels and recording the drop in power output.

It shouldn't take more than a few minutes to try shading one cell, 2 cells, maybe laying a line across the panel to simulate a halyard or something. Then they can post their findings and we'll know for sure.
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Old 26-05-2015, 19:52   #82
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Re: Solar Panel efficiency - Should I upgrade

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Originally Posted by DeepFrz View Post
So Jack, you have tested Sunpower cells (C-series? or X-series?), have you tested panels?
Would love to test them, but I doubt they'd let me take them for a test ride. Thanks for the reality check though - good idea- maybe Consumer Reports would be helpful or some other independent source. Off to check...
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Old 26-05-2015, 20:34   #83
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Re: Solar Panel efficiency - Should I upgrade

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Originally Posted by socaldmax View Post
Yes, cloudy days can still produce a surprising amount of power.

There is also a refraction effect caused by the edges of moving clouds. This quote is from a solar installer site.
I fully understand that effect. However I was stating that output was with full cloud cover and occasional drizzle yesterday
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Old 26-05-2015, 21:15   #84
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Re: Solar Panel efficiency - Should I upgrade

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I fully understand that effect. However I was stating that output was with full cloud cover and occasional drizzle yesterday
And how were you measuring the output?
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Old 26-05-2015, 22:06   #85
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Re: Solar Panel efficiency - Should I upgrade

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And how were you measuring the output?
Fluke at the battery
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