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How To Find Out The Wattage Of A Solar Panel


peasemold
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I have just been given a solar panel but do not know what the wattage is. There are no labels and the previous owner does not have a clue.

 

Is there a way to discover its wattage. I have a multi meter and very basic knowledge!!

Freelander 2 chased by a 2011 Unicorn Valencia

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Type for type it will be roughly proportional to

the area.

So measuring it and looking at the products advertised will give you a starting point.

By "type" I mean, if it is crystalline or amorphous; amorphous looks like as used on cheap solar garden lights, crystalline tends to be intensely black or blue and has hints of the crystals if looked at obliquely. There are differing crystalline sub types but the performance between them is not very different.

Edited by JTQ
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A 15 watt will produce 1 amp per hour output approx in bright sunlight.

 

http://www. sunshinesolar. co. uk/khxc/gbu0-catshow/1. html?gclid=CLvKq6S4sLwCFQsCwwodsj8AiA

 

Lot of info on this site. .....

Ford C-Max and Coachman Festival 380/2 SE 2006    Motto  Carpe Diem

Still trying to find the perfect pitch. ..110 amp Battery+ 65 watt roof mounted Solar and 25 watt Wind Turbine. LED lighting. Status Aerial 315. Loose chattels marked with UV,. Safefill Gas Fitted.

 

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How big is it. Get some idea of its area and then have a shufti at what's on the market at roughly the same size. You probably won't be all that far out.

Solar panels are rated assuming that the sun is directly perpendicular to the panel and virtually on midsummers day

2018 S-Max Titanium 2. 0 Tdci (177. 54bhp,180ps,132kw) Powershift + 2015 Unicorn III Cadz, Ventura Marlin porch awning

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So, I found out that: Power in Watts (W) = Current in Amps (A) x Voltage in Volts (V)

 

I then went here:

 

http://www. selectsolar. co. uk/cat/171/testing-your-solar-panel-regulator.

 

I measured the open circuit voltage and the short circuit current, multiplied them together to get the Watts.

 

Does that sound about right?

Freelander 2 chased by a 2011 Unicorn Valencia

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This will give you "a" figure but i'm not sure how useful it would be (shorting out a PV panel doesn't sound like a good idea either) because no real usage would ever result in either of those measurements i. e. the panel will never be open nor short circuit in real use. If you have a multimeter you could try attaching a known load (e. g. a resister) and when directly facing bright sunlight (i. e. perpendicular) measure the under load voltage and current.

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When you do finally find out, or get a rough idea of the wattage of your panel, there's loads of useful stuff on this C&CC factsheet (which can also be downloaded) http://www. campingandcaravanningclub. co. uk/helpandadvice/technicalhelp/power/solar-power

The traveller sees what he sees, the tourist sees what he has come to see (GK Chesterton)

 

There's no such thing as bad weather, only the wrong equipment (Alfred Wainwright)

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The best way to measure the output is to put a line fuse between the controller and the battery and measure the current with a Maplins current tester. Wait for a bright day at noon (you might wait awhile!) and multiply the current showing by the battery volts. This will give the true wattage of the panel. The rated wattage will be some 20% greater, but you never get it.

 

I use this tester regularly on site to see what is happening. The max I have seen from my 50W panel is about 2. 9 amps and 12. 6v at the battery. =36watts.

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Chris in Warwickshire, Elddis Odyssey 482 (2008), Mitsubishi Outlander diesel, 2017

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The best way to measure the output is to put a line fuse between the controller and the battery and measure the current with a Maplins current tester.

 

The challenge associated with this approach is that the current will depend entirely on the state of charge of the battery. If full, the controller is not going to shove more current into it. I don't feel this would be the best method of measuring PV output, imho.

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The challenge associated with this approach is that the current will depend entirely on the state of charge of the battery. If full, the controller is not going to shove more current into it. I don't feel this would be the best method of measuring PV output, imho.

Measure things with the water pump running?

 

The rated wattage will be some 20% greater, but you never get it.

 

 

 

I have seem more from my Kyocera 85 Watt panel than its published rating, just but nevertheless actually more. With a Morningstar controller and using its matching meter.

Edited by JTQ
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The OP wanted to know the wattage of their unlabelled solar panel not what it would supply given a particular scenario e. g. battery charging, powering a water pump etc. PV power output is already quite variable (e. g. maximum power point), introducing more variability might not be the best approach. Measuring PV current through a know load e. g. a 10 ohm resister would remove the vagaries of the battery side of the controller. 25V through 10 ohms is 2. 5 amps, which is a reasonably representative load for a caravan's DC services. A 10 ohm resister wouldn't be more than a quid from Maplin.

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Using the tictag method above (and a friend!) I have managed ascertain that I have a 20w panel.

 

Should do to get started.

 

Thanks for all the tips and advice.

Freelander 2 chased by a 2011 Unicorn Valencia

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You are welcome. We are both working on PV panels right now! I've just fitted three x 100W panels and will hopefully fit the remaining three tomorrow. I fully intend to making my favourite espresso coffee paid for by mother nature!

 

p. s. Actually, I'm not sure if the sun comes under 'mother nature'....

Edited by tictag
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PS The 10 ohm resistor needs to be of adequate wattage; 25v at 2. 5A is 62. 5w. People tend to forget that you are dealing with some serious amounts of energy from solar panels as they sit there looking demure and calm. A 100w 10ohm resistor is about £3. 50, so not a huge amount more, but you must spec accurately.

Enjoy every minute of every day. It doesn't last nearly as long as you'd like, and there's no guarantee of coming this way again.

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