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Ebay "Camping Solar Panels" listings with impossibly high power ratings

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The spectral response of the panel is also important. That solar intensity measurement of 1000W/m^2  is for ALL wavelengths that can pass through the atmosphere, from UV through IR. Your solar panel likely has a certain spectral response curve, which only makes use out of a portion of the available wavelengths. I wouldn't be surprized if your solar panel could only use 50% of the available wavelengths (and with many of those only slightly contributing to the electrical output of the panel). So maybe a 30% to 40% actual panel efficiency. My guess is that the specs provided by the manufacturer were based on simply multiplying the solar intensity by the surface area of the panel, and NOT taking into account the panel's efficiency, resulting in an artificially high maximum output power being stated in the specs.

I assume that the specified power of a panel to be that which can be achieved in ideal natural conditions. i.e. clear sky, i.e. minimal atmospheric attenuation but still what can be achieved in the natural environment. Sure, if I concentrate sunlight via mirrors I'd be able to make any panel push whatever power you want (before melting it that is) but that's not the expectation when a customer sees the power specification.

Sure, If I was seeing around 75% of the specified short circuit current, I might doubt myself, but these panels were producing far less than that.

Covid's put the cabosh on the whole trip now I'm not in a rush to get the panels sorted out.

I am planning to get some older model 300W roof panels and trying them out. My roof panels seem to generate much closer to the specified current (80%) and they're not even oriented optimally so maybe I raid my roof panels :-)

The standard condition for the PV panels are 20°C temperature of the cells and 1000W/m² with an AM1.5 spectrum. That is the wavelengths if the light goes through 1.5 times the normal clean air. So this would be a clear sky day with the sum coming in at some 40° Angle.  So the winter conditions may be relatively close to the standard. The temperature  mainly effects the voltage and has little effect on the current. Here low temperature may actuall reduce the current a little (like a few percent - so still not relevant). Because of temperature even legit panels  don't get the nominal power very often (maybe on a sunny day in spring with some wind).

The current usually does no depend much on the voltage at the panel, as long as the voltage is well below the MPP or open circuit voltage. So the maybe 1 or 2 V drop at the cables and meter does not make a big change. The main point is the angle of incidence (can be calculated from the cosine) and the actual intensity. This can vary a bit with more or less mist and humidity in the air which effects the NIR part and is not directly visible to the eye. So the roof mounted PV panel could help has an indicator.

24% efficiency would be really high end. Possible but only at a price - more like premium grade for maybe a solar plane of solar racer.

Half the claimed current would be around 12% efficiency - more like the polycrstalline grade. It should be visible if the cells are mono or poly type.
One should still be very confident in the meter to measure the current - there are fake panels, but also broken DMMs.

Lots of flexible or ”camping” power panels on ebay that have no way to produce the stated watts as they don’t even have enough surface area to produce the advertised watts.  No need for complicated measurements when 500x1000mm panel claims to output 300w 🧐

90% of the flexible panels from chinese junk sellers are suprisingly … junk with only 30% power. 

Forgot to mention that I have been looking for flexible panels also by myself and it seems like good one are lot more expensive than rigid rooftop panels. Not really suprise considering the production volumes.


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