How much am I getting ripped off for my solar panels?

[GILow]

Originally Posted by lawrence_craig

See the attachedAttachment 188416

Today was an average day, 2 days ago was a very good day.

Reading that data log I get the impression the battery bank is not reaching float. Could be a problem in the medium to long term.

[smac999]

Which controller? The 15a or 30a? If you are using the 15 you might be maxing out the controller.

[keith001]

Originally Posted by GILow

Sorry, I know that response was not to my post, but I have to disagree or at least clarify for the OP. I do regularly extract 360 watts from my 380 watt banks. Sure, only at the middle of the day, but it is possible, and indeed should be expected.



A properly functioning and well installed system should reach its peak theoretical output at least briefly. But as StuM notes, you then need to take that figure and apply it as a 4 to 5 hour day.

Agreed. Should get rated capacity during peak.

[StuM]

Originally Posted by GILow

Just read this again... 15 volts peak seems pretty high to me, if that is on the battery side. Off the top of my head I can't think of a battery chemistry that likes that kind of charging voltage.

What sort of batteries do you have?

I'd assume that's on the panel side and sounds about right. Most 12V panels have a peak voltage (Voc) of around 22V aand a max power voltage (Vmp) of around 17-18V at STC (1000W/m² insolation, 25°C and an Air Mass Coefficient of 1.5). In the tropics, you'd expect it to be a bit lower, largely because of the panel temperature.

[Fore and Aft]

Keith001 you are not wrong about the dirt. On our house solar system that hardly perceptible layer of dirt really effects the panels capacity.
Cheers

[GILow]

Originally Posted by StuM

I'd assume that's on the panel side and sounds about right. Most 12V panels have a peak voltage (Voc) of around 22V aand a max power voltage (Vmp) of around 17-18V at STC (1000W/m² insolation, 25°C and an Air Mass Coefficient of 1.5). In the tropics, you'd expect it to be a bit lower, largely because of the panel temperature.

Maybe, but I’d be surprised if the op has the kind of mindset to be measuring on that side of the regulator. I mean I am a total electron nerd (excluding your own electro-unit-aware-presence of course) and I don’t go measuring the panel side even when I am bored.

Does the victron app report this data? Can not see it on the posted screen grab.

[GILow]

Originally Posted by Fore and Aft

Keith001 you are not wrong about the dirt. On our house solar system that hardly perceptible layer of dirt really effects the panels capacity.

Cheers

One layer of shifting spanner is pretty bad too.

[StuM]

Originally Posted by GILow

Maybe, but I’d be surprised if the op has the kind of mindset to be measuring on that side of the regulator. I mean I am a total electron nerd (excluding your own electro-unit-aware-presence of course) and I don’t go measuring the panel side even when I am bored.

Does the victron app report this data? Can not see it on the posted screen grab.

Yes, it does. It's the "Solar Panel Vmax" value. Best was 20.22V "one day ago" when the highest output through the day was 178W. Maximum battery voltage that day was 14.03V.

[motion30]

Originally Posted by ozsailer

Off tangent but can you advise what brand of flexible solar panels you have bought. 23 to 25% efficiency is the highest I have heard. Can you copy the data sheet please and post


Greg H

my thoughts exactly

[GILow]

Originally Posted by StuM

Yes, it does. It's the "Solar Panel Vmax" value. Best was 20.22V "one day ago" when the highest output through the day was 178W. Maximum battery voltage that day was 14.03V.

Oh dear. 0 out of 10 for observation to me. [emoji853]

[Dsanduril]

With the equinox having just passed if you are in the Caribbean you should be getting very close to overhead sun, and sometime in the next 6 weeks it will be. If the panels are flat then you should see rated power, temperature corrected, if there is no shade.

For 23-25% efficiency panels I would expect about -0.5% temperature factor per degree C. That’s panel temperature which is likely about 30C above ambient, which is likely 25-30C in the Caribbean (on the water). Long way of saying I’d expect to see 15-20% less than nominal rating or 240-255W output at noon.

That all assumes the batteries are empty enough to take that much. If they are, and you don’t see around that value then I’d start hunting for problems. That’s at noon with no shade, so first step is to make sure you can test reliably under those conditions and not get yourself hung up when it is really either a shade or an orientation problem.

[lawrence_craig]

Originally Posted by Dsanduril

With the equinox having just passed if you are in the Caribbean you should be getting very close to overhead sun, and sometime in the next 6 weeks it will be. If the panels are flat then you should see rated power, temperature corrected, if there is no shade.

For 23-25% efficiency panels I would expect about -0.5% temperature factor per degree C. That’s panel temperature which is likely about 30C above ambient, which is likely 25-30C in the Caribbean (on the water). Long way of saying I’d expect to see 15-20% less than nominal rating or 240-255W output at noon.

That all assumes the batteries are empty enough to take that much. If they are, and you don’t see around that value then I’d start hunting for problems. That’s at noon with no shade, so first step is to make sure you can test reliably under those conditions and not get yourself hung up when it is really either a shade or an orientation problem.

Ok, that’s very helpful. My batteries are normally at 12V by midday. How much would it need to be at before I was to see 240W?

Thing is, if I am close the equinox, should I not at least be expecting to see around 200W? The highest I’ve seen is 150.

With regards to temperature, they are slightly raised off deck to allow for cooling.

Sorry if some of the questions/statements are of, this is pretty new to me.

[lawrence_craig]

Originally Posted by motion30

my thoughts exactly

[CaptainJohn49]

The "equinox" just means that the sun has crossed the equator. It's still at 0 degrees North. Depending on where you are it could take a while to be overhead at your location. I'm certain most know this but I thought I'd point it out for those who aren't into celestial navigation.



My take on solar panels is simple. Claims of wattage are a driving force in sales. I have one 135 watt panel and I just figure about 50% percent output on a good day.



CaptainJohn49

[skipgundlach]

Having read the thread, I conclude I am far out of touch, as I had not heard of fixed panels in that efficiency range (and no manufacturer I have seen, yet, see above as to currency, cites efficiency as a range).

As well, I had been under (perhaps mistaken) the impression that flexible panels were historically of less efficiency than fixed panels, and that Sunpower had far and away the best efficiency of all cells, to the degree that other panel vendors buy them and label their panels as containing Sunpower cells.

From their site: "SunPower produces the highest efficiency monocrystalline solar panels available. Our X22 has a record-breaking efficiency of up to 22.8 percent, making it the best performing panel on the market today."

Note "Up to 22.8", not "23-25", % efficiency.

So, if real, some other company has stolen a march on SunPower. Who makes your flexible 23-25% efficient panels?

No argument with the other explanations for less-than-full-power, space considerations, etc. ...