Solar: Wattage output

[Fearnow]

I purchased 2-100 watt panels from Renolgy and seeing only 114watts on the best of sunny days. My MPPT controller measures what is coming off the panel along with battery absorption. I assumed I would get close to 200 and have made several calls to the seller but no response. Any ideas?

[sailorchic34]

Panel rated output and actual output, does actually very. Generally 60 65% it's as good as I ever get. The issues of course is panel output drops with temperatures above 68 degrees Fahrenheit and if the angle of the panel isn't correct for the latitude and if there's clouds are Haze in the atmosphere. All reduce the rated output

[StuM]

Are the panels horizontal (not tilted towards the sun)?
Is this around Annapolis (39° North) over recent months (winter)?.



If so, that's about all you should to expect.

[Fearnow]

Ok. For 3 days I have been looking for an answer to what I thought was a simple question. Thanks!

[Fearnow]

Originally Posted by StuM

Are the panels horizontal (not tilted towards the sun)?
Is this around Annapolis (39° North) over recent months (winter)?.



If so, that's about all you should to expect.

Yes, Annapolis and the readings I got were the other day when it was about 70 F
The panels tilt and were facing directly at the sun on a very clear day. Ha, hard to believe a clear day in Maryland lately.

[john61ct]

The SC only puts out power when a load is pulling it.

As SoC climbs, energy will flow much more slowly until only a fraction of the potential available.

You need a heavy but controlled load to test, and a known good ammeter, don't trust charge source readouts.

[thomm225]

Originally Posted by Fearnow

Yes, Annapolis and the readings I got were the other day when it was about 70 F
The panels tilt and were facing directly at the sun on a very clear day. Ha, hard to believe a clear day in Maryland lately.

It could be something as simple as your connections.

Sometimes when I have two panels hooked up to the same controller, and I don't see the expected wattage I usually can move the wires with my hand and the watts jumps up to where they are suppose to be which is why now I have my 65 watt panel on my Victron MPPT controller and my 50 watt Renogy panel on my PWM controller .

It's working much better with this setup

[john61ct]

Unmatched panels should be on separate SCs anyway

[Group9]

We had 280 watts on our boat for five years. I think I figured a maximum theoretical 12v amperage at around 26.5. The most we ever actually saw was 22.1 with the sun at what appeared to be 90 degrees to the panels. Mostly. we seemed to max out at around 16 amps. Our panels were fixed and we never made any effort to aim them.

[john61ct]

The key indicator is Ah per 24 hours.

Varies by seasonal day length of course away from the equator.

a 300W 12V nominal system averages around 100Ah in good conditions

[ohgary]

Originally Posted by Fearnow

I purchased 2-100 watt panels from Renolgy and seeing only 114watts on the best of sunny days. My MPPT controller measures what is coming off the panel along with battery absorption. I assumed I would get close to 200 and have made several calls to the seller but no response. Any ideas?

Are you panels tilted to flat? Also are you sure you have a real MPPT controller?

[Sailing Drummer]

+1 to what StuM said. In the summer you'll get a little more. But don't expect too much that far north. I was surprised when I wasn't getting what I thought I should get either in the upper Chesapeake. Get farther south and you'll start to see a difference.

[Captain Bill]

If your batteries are near full charge your controller may be throttled back. Since you didn't mention the specific controller we can't tell what information you are getting from it. If your controller gives you the the mpp and the current panel voltage and the panel voltage is higher then your controller is throttling your output. If they are the same then the controller is putting out as much as it can. Also you will only get maximum power near local solar noon which in your case is close to 1300 edt. If you are looking at any other time it will be less than optimal. Between 1200 and 1400 it won't vary too much but it will be significantly lower before and after that. If your panels are at absorption voltage then the controller is throttling your output and limiting your power production which is normal.

[Cpt Pat]

That output (a little over 50% of rating) doesn't sound unusual. If you want 100% output, you'll have to test at the equator, on a perfectly clear sunny day, at noon, on either of the two days per year that are at equinox. I'm half kidding, but really, the ratings are for ideal conditions.

If you want exact numbers, here are the calculations: https://www.itacanet.org/the-sun-as-a-source-of-energy/part-2-solar-energy-reaching-the-earths-surface/

But generally, as a rule of thumb for mid latitudes, it's about 1,000 watts per square meter X the panel efficiency -- under ideal conditions. So a one square meter panel with 17% efficiency should output approximately: 1000 X 0.17 = 170 watts at 25 degrees C surface temperature (NOT ambient temperature). I'd be pleased to see 100 watts from such a panel on a clear day at noon at 38 degrees latitude, on summer solstice. You will never see the rated output unless the manufacturer was struck by a sudden desire to be overly honest (and therefore non-competitive with the other weasels).

[Fearnow]

Haha, still laughing at some of the comments. I hope to be back in the Carib by November and will check the stats then.

I purchased a PowMr MPPT Charge Controller 60 amp 48V 36V 24V 12V Auto - Max 190VDC Input LCD Backlight Solar Charge for Vented Sealed Gel NiCd Lithium Battery【Software Update Version】(MPPT-60A) with Lithiums coming in the next week. I am planning to add another 800 watts, but wanted to see the quality of these panels first.

Really appreciate all the help!