Solar testing during day.

[nothing to lose]

Well this was just a quick little test, I saw a post by Wiredwrong asking about info for a daughters school project so I did this with 1 HF 15watt panel, almost new.

I had to workj in yard nearby anyway, it was a perfect sunny day, no clouds to see all day, and I was too hot all day, so a good day for solar testing I geuss. Central USA, South Central MO.

I did not find the fan to test amps with untill later so

Time   open volts   short circuit amps    Fan load amps   Watts?

T 9:30     22V          0.63A                N/a          13.68W

T10:30     20V          0.66A                N/A          13.20W

T11:30     19.84V       0.79A                0.60A        15.67W

T12:00     19.94V       0.81A                0.62A        16.16W

T 1:00     19.54V       0.83A                0.63A        16.22W

T 1:30     19.42V       0.82A                0.63A        15.945W

T 2:00     19.38V       0.82A                0.63A        15.891W

T 3:00     19.72V       0.75A                0.59A        14.79W

T 4:00     19.77V       0.66A                0.53A        13.048W

T 4:30     20.2V        0.42A                0.40A         8.484W

It is now just after 4:30PM here, I post this now cause I may be gone later, if here I'll get a few more readings to post also. Even though the panel is in full sun it looks like at 5:00 there won't be enough watts to worry about checking. Although still very bright and sunny out, the sun seems to be behind an over cast a bit perhaps but not a cloud as such.

Well we see in the morning the volts were higher and amps lower, volts dropping till about 2PM while amps were rising till about 1pm then started dropping while at 3pm the volts started to rise again. The readings were always taking in what looked like clear sky, no visable clouds, also in full sun, no shadows on the panel. The panel was never moved at all. It was placed at a slight angle on a minvan roof to let the heat out from under it, one end on roof other end on cargo rack bar, never changed all day.

It is nice to see that so far my 15watt HF panel puts out more than 15watts from at least 11:30 till 2pm, perhaps longer.

The fan I tested the load amps with was a $10 6" auto type that plugs into a cigarette lighter socket. At 13.5V running from a battery the amps for the fan was 1.17A. Durring the testing when running the fan direct from the solar panel, the higher the amps the faster the fan ran of course. At 0.40A just now it was moving some air but running slow.

If you notice I did not get a 12:30 reading, that is because while getting the 12:00 reading I got a racoon in my little motor home I left open and unattended and at 12:30 I was chasing him out. Ever see RV with Robin Willians :0

 I been feeding the little bugger at the porch and he comes up to my foot, and 6" to my hand, but still I don't want him in the motor home!

[johnlm]

Multiplying short circuit current times open circuit volts does not give you the output wattage.  The real wattage at open circuit is 19V X 0 amps = 0 watts, same concept goes for short circuit current resulting in nearly 0 V hence 0 watts out.

You need to multiply the output voltage time the current you have while you have a reasonable load on it such as you might have had with your fan hooked up.

Johnlm

[nothing to lose]

T5:45  20.3V  20.3 amp  fan 0.27amp but running slow and poorly.

I moved the panel angled a little more towards the sun now at the last reading and it went up to 20.5V 0.33Amp and the fan ran better at 0.31 amp but still slow.

Sun is now going behing trees so last reading was 5:45pm

[nothing to lose]

Ya, it should work that way like you said I geuss. But I was charging a SLA 17amphr battery except when I disconnected it to test the open Volts and short circuit Amps and the fan.

Battery volts X charging amps was equaling about the same watts as I posted. I just didn't post the battery stuff as it would have perhaps confused things a bit more. Durring the day one SLA was full charged and I switched to a less charged SLA to  charge it up some also. That would have caused the volts to rise durring the day then suddenly drop due to switching batteries. Also the voltage shown would then have been the battery volts, not the volts of the panel itself. Also the amps would then be based on the battery volts as well to a point not the amps of the panel. So with the battery charging I was getting the same watts, but showing those numbers does not realy show what the sun was doing with the panel as the battery was different volts and amps numbers, only the watt numbers would be the same.

I probably should have wrote those battery numbers down and posted them also, but I just checked them and didn't keep track since the watts were working out the same.

The watts are in line with what the panel should have been producing also. 15watt panel ranging from 13.68-16.22watts and back down to 8.44watts again in evening.

This being a nearly brand new panel it should be making a little more watts than actually rated also.

[richhagen]

Interesting, I am guessing that the higher panel temperatures during the afternoon drove down the open circuit voltage.  I am aware of that occurrence, and the charts from panel manufacturers indicating this, but is is interesting to see your empirical data from an amorphous panel.  Rich

[johnlm]

Wow, well over 16 W out of a 15W HF panel.  You must be lucky to get one that does that.  The HF 5W panels I bought a couple of years ago were lucky if they put out 3.6 W max when new and now they do about 2.5W when charging a 12V battery.

Johnlm

[ghurd]

If you have an amorphous PV, and follow the discussions about 'shading' a crystalline PV, then try shading a single 'stripe' on the amorphous PV.

Like on my porch with wrought iron decor. My porch piece shadow is the same width as my amorphous PV stipes.  The argument goes right out the window.  It seems worse than shading a single mono or poly cell.  

Shading perpendicular to the stripes seems proportional to the exposed surface area.

I suppose other amorphous PV will act different because there are so many variations.

Interesting stuff.

G-

[wiredwrong]

Thank you so much , you did not have to do this for us yet you did. If I ever get a chance to get out of this state(Oklahoma)I'll make it a point to swing your direction with a nice big bottle of...insert poison of choice here..., Also I think I may go get 1 of the 15w HF panels and repeat the experiment here to compare numbers, see if the insolation charts match up real world data. Thanks again.

Randy33 OKC,Ok.

[nothing to lose]

This was just one panel, it comes as the kit of 3 panels, controller, 2 5watt 12V CLFs.

$250 regular price, on sale allot for $200 and I got them allot cheaper with a coupon sent to me from a friend. I have 9 of these panels total, 3 kits.

It took a little time messing around but not a problem, I was working in the yard close by anyway. Happy to do it, and I learned a few things also myself. I should have actually done this before. Right now I still have the panels on temporary mounts, like the stands that came with them and in the back of an old truck etc.

Things I learned is the way I was going to mount these permanant later would be wrong! And while messing with this panel yesterday I was watching the sun track all day, I do have a spot that stays in the sun without any shade from sun up untill about 4PM, after 4PM the power gained is not really enough to worry about losing from the shade of the trees. As summer progresses it will be later in the day also before that those trees shade the panels. That spot in winter should not be shaded at all as the sun sits lower in the sky and misses those trees. So I found the closest to perfect spot for my panels yesterday.

I also see that I need to move the tempory setups to other locations and angles. The sun has shifted and trees have bloomed since I set them up.

Although it's nice to live in a woods it does have it's problems. The trees block the wind making short towers for testing kinda useless and they block the sun making it difficult to locate the solar panels.

[nothing to lose]

When I first got these about a month or two ago I set up 3 panels from a kit on the stand they came with, they all did ok but each of the 3 varied in open volts and shorted amps some. The sun was not as good then as yesterday.

So many things can change test results like this though, alittle more or less haze while testing one panel than when testing another, and we don't really see the minor haze enough to notice a slight diffence that could lower the numbers a tiny amount.

[Bruce S]

NTL:

   I trade my city for your woods:-)

Your number are pretty much in line with what I have seen. I am in the process of getting the parts to build a tracking system for mine. Something similar to David HK's design.

Also the peak times versus heat is spot on....

Go find a fan 24Vdc , or get one of the new ones that are built for P4s , these are highly effiecent and mount it so it can tap a little of the power to cool the back of those panels.

I am using a little 5 watter to cool back of mine!!

I noticed too that even though the sun was on the panels longer the output was peaking early so I hooked up a 24Vdc 120mmx120mm fan to just circulate air around the back of these. I would use a timed water system ( drip irragation hose type?) but don't have one:-) had the fan and riding motorcycle so the panel was available.

Power is better now.

House is probably acting like big heater on back side right now so I'm looking into remounting the panels.

Cheers

Bruce S

[nothing to lose]

As johnlm mentioned the watts may not be correct. Yesterday was bad sky and storms here.

Today very nice and sunny but a little hazy. While playing and testing today I discovered the battery I used was shot. After charging it up and sitting 2 days it shows 12.1V but the tiniest load drops it to nothing. Also the volts jump up too high to fast when charging I found today.

Today I was using a 35 or 50 watt Arco and 3 HF panels. The Arco was putting out 18V open and into a GOOD battery was about 2.3 amps. The HF panels should be 45watts, they were showing 22V open and into same battery only 1.31amps, but they were going through a controller the Arco was direct connection. The Arco was at least one full amp higher going into a battery it seems.

Also I had 2 other HF panels side by side, 1 was putting out about 22V open, the other only 18V open. I was going to use both panels to charge up some 19.2V Bruce packs but 18V is not high enough so I am only using one panel

I found another panel at 0V open today also! Wiggling the wires at the little black box it would put out 22V open if I held the wires in place. I took off the cover and found the screw was loose and the ring terminals just flopping around. I tightened those and it was charging a battery fine. Later I checked and 0V open again and battery at 11.9V!

 I checked the wires at the panel, 0V there, twist the panel just a little and I get 22V again! Twisting the panel to get power is NOT an option! I will have to check this one better and see what's up with that, it may be going back to HF!