Cabin Solar during Winter

[Scoutmaster]

So I have 4x 100w panels at my cabin only producing about 20-30 watts this winter. Is this normal? I only get 2-3 hours of indirect sun.

 

[sunshine_eggo]

I see no sun. 20-30W in those conditions may be fantastic.

I see a little snow on the panels. Any snow at all can adversely affect production to a shocking degree.



The snow on the bottom row of cells here is likely reducing this panel's total output by 50%. If you have shade/snow on ANY cell in a column, that one cell limits the entire column.

Critical that your panels be completely snow free frame to frame and make sure the "snow drift" or snow balls at the bottom don't cast a shadow.

Get your panels completely cleaned off and re-evaluate them at your peak solar time.

Another inhibiting factor is if your batteries are fully charged or in absorption. if that's the case, the PV will only produce what is needed to maintain the battery at the prescribed voltage. You can test this by running a load that's greater than the array rating to force the array to output everything it has.

 

[Scoutmaster]

Thanks ?
I’ll have to experiment. I’ve been running the generator to charge my battery. I’m in the mountains so it’s going to be difficult to keep them snow free. I need to mount them vertical to keep the snow off. I was just surprised that only 20watts of power was coming in mid-day.
I definitely overestimated how many watts I could pull from just 4x100w I anticipated at least 100w for 3-4 hours hoping it would keep my battery happy. I actually think the solar controller and blue tooth dongle might actually be using more energy than the 400w of solar can create in the winter.

 

[sunshine_eggo]

Thanks ?
I’ll have to experiment. I’ve been running the generator to charge my battery.

If your battery is at a high state of charge because of this, the PV might not produce much.

I’m in the mountains so it’s going to be difficult to keep them snow free.

It's a daily thing. Get a plastic scraper and a broom. Pitcher of cold water and a squeegee.

I need to mount them vertical to keep the snow off.

Will help.

I was just surprised that only 20watts of power was coming in mid-day.
I definitely overestimated how many watts I could pull from just 4x100w I anticipated at least 100w for 3-4 hours hoping it would keep my battery happy.

Unless you're in the Arctic, in full sun, with clear skies, no shading or snow, I would expect at least 200W. Haze, snow, shading, etc., can hurt PV production substantially.

I actually think the solar controller and blue tooth dongle might actually be using more energy than the 400w of solar can create in the winter.

Hopefully, not.

Can the wood frame cast a shadow at the bottom of the panels?

 

[MisterSandals]

I only get 2-3 hours of indirect sun.

You're lucky to get anything with indirect sun.

What SCC do you have and how are your panels arranged? All parallel? 4S? 2S2P?

There are array options that would raise your voltage if that is part of your issues. Your pic shows only 13.2V from solar. You NEED to get this up to at least 5V above battery voltage (where most SCCs start charging). Putting your panels in series will help if your SCC will accept the increased voltage (see your SCCs max input voltage, temp adjusted on Voc).

But it sounds like you need to get direct sun whether its by moving your panels or tilting them.

Need more info to provide more (some?) help.

 

[Scoutmaster]

You're lucky to get anything with indirect sun.

What SCC do you have and how are your panels arranged? All parallel? 4S? 2S2P?
4 in Parallel.

4 Parallel
I have the Renology Wanderer…

Renogy 200W 12V Monocrystalline Solar Panel Bundle Kit with 200W Solar Panel, 30A Charge Controller, 9in Adaptor Kit, A Pair of Branch Connectors https://a.co/d/ft564lW

There are array options that would raise your voltage if that is part of your issues. Your pic shows only 13.2V from solar. You NEED to get this up to at least 5V above battery voltage (where most SCCs start charging). Putting your panels in series will help if your SCC will accept the increased voltage (see your SCCs max input voltage, temp adjusted on Voc).

But it sounds like you need to get direct sun whether its by moving your panels or tilting them.

Need more info to provide more (some?) help.

I think it’s all set up correctly.
It does say 13.2V for the solar?
I have 4-100w panels on parallel.

The snow came early this winter so I just put them on some 2x4s and move them around.
My roof dumps the snow off violently so i have to move them around to keep them from getting buried. My cabin faces the mountain so I have 2000vertical of a hill and 100ft trees blocking the sun. In the summer when the sun is higher I get good afternoon sun. This is only my first real winter trying to get some Solar…. and I’m starting to realize I get very little if any direct sunlight.
I’m very happy I didn’t mount them to the roof of the cabin or they would literally be buried in snow and ice.
I’m starting to realize a good battery charger and my generator might be my only realistic options.

 

[MisterSandals]

It does say 13.2V for the solar?
I have 4-100w panels on parallel.

Its in your pic...


But looks like that SCC has very low max input voltage.

• Max. PV Input Voltage: 25 VDC
<panel> Open-Circuit Voltage (Voc): 24.3V

Kind surprised the panel Voc is so close since the temp compensated voltage, based on your winter wonderland photos, is probably over 25V (very likely to damage the SCC).

 

[Scoutmaster]

I wonder if the SCC is damaged already.
We get -15 easily and have already seen 0.
It was cheap like $40 so can buy a new one.

I bought an lv2424 but I don’t have the solar ability to realistically run it at 24v. I’m on forest service land so I can’t cut trees or build anything easily.

I need to go back up the cabin and play around… it has been difficult with the snow storms and lack of sun to experiment. I just bought the blue-tooth dongle so didn’t have a clue if the the panels were working properly.

This past summer with 2-100ah SOK’s I was doing very well …i upgraded to the 24v AIO lv2424 and it toasted one of the batteries so I’ve been nursing 1- 100ah Sok for the past month. I can’t tell if that battery is toast also or my solar system/ charger/ or maybe something else is wrong. It’s difficult to experiment in the snow/ice and I have to ski or snowmobile in just to see…

 

[sunshine_eggo]

Hard to toast them. What happened?

 

[12VoltInstalls]

4x 100w panels at my cabin only producing about 20-30 watts this winter

Parallel universe: https://diysolarforum.com/threads/when-the-sun-migrates-for-the-winter.50802/
35 watts is what I’m doing this overcast day in Vermont or of a normal ~400W

 

[PunchySunshine]

Parallel universe: https://diysolarforum.com/threads/when-the-sun-migrates-for-the-winter.50802/
35 watts is what I’m doing this overcast day in Vermont or of a normal ~400W

I harvested 2 kWh yesterday from my 4 KW array here in Colorado. Worst day of the year!! :D One more week until SOLSTICE!!

 

[12VoltInstalls]

Get this charge controller and do panels 2S2P and face them SSE and SW

 

[MichaelK]

Here is another option for you if you can't cut trees. With a controller with a higher voltage limit (Tracer 5415AN), you can wire the panels for high voltage, and then position them 100-150' away from your cabin in the best location you can find. You can do that, and also implement 12VIs suggestion of arrays facing in different directions, and double the number of panels. You'd have 4S2P, but only one array will be a full power at a time. You'll dampen the noon peak, but broaden the power curve over the course of the day.

 

[Doggydogworld]

I wonder if the SCC is damaged already.
We get -15 easily and have already seen 0.
It was cheap like $40 so can buy a new one.

Renogy Wanderer is a PWM controller. Until you near 100% SOC it directly connects the panel array to the battery. When you do that panel voltage drops to match the battery charging voltage. In your case that's 13.2V, perfectly normal for LiFePO4. If you unplug the panels from the SCC and test the open circuit voltage directly it will be much higher, maybe 25V with your weather.

The comments above about keeping each cell clear are spot on. Your panels have 36 cells in series. If snow/shade/etc. reduces a single cell's current by half the current of the other 35 cells will drop to match. If you block one cell completely output for the entire panel will drop to near-zero.

Also as mentioned above, your controller may use 13.2V as the cutoff to switch from bulk charging to absorption. These are really lead-acid terms, but SCCs tend to use the same approach (with different cutoff voltages) in their lithium profiles. In absorption mode it can limit panel output to protect a nearly-full battery from overcharging. There should be a way to find out what mode your SCC is using. You can also drain your batteries to 50% SOC or so and see if your panel output is higher. Not sure it'd make much difference with the dim lighting pictured, though.

A MPPT controller will also pull more power from the panels in most conditions. They use voltage conversion to hold the panels near their max power point (closer to 20V) while charging the battery at 13.2V.

 

[Scoutmaster]

12VoltInstaookmark​

and face them SSE and SW​

?
I’ll attempt to upgrade the controller and move a few panels around this winter. It does seem like the Lower voltage and snow on my panels is a problem.

Thanks for everyone’s input. This will be the first real winter to learn what works and what doesn’t. I really hope to have 20-30 years to get this system dialed.

 

[Miniovic]

It is not uncommon for solar panel output to be reduced in the winter months due to shorter days and less direct sunlight. However, a reduction in output to 20-30 watts with 4 panels seems very low, even with only 2-3 hours of indirect sunlight. There are several factors that could be affecting the performance of your panels, including:

• Shadows from trees, buildings, or other objects
• Snow or ice accumulation on the panels
• Damage to the panels or their connections
• Poor panel orientation or angle
• Malfunctioning inverter or other system components

I recommend having your solar panel system checked by a professional to determine the cause of the low output. They will be able to identify any issues and recommend repairs or maintenance to improve the performance of your system.

 

[Ptom]

Trees? No problem! All it took was 3' diameter pipe with a 5/8" wall, 10 yards of concrete in a 12' deep hole, and my 30 ton boom truck to set it all into place. Nothing has moved in 15 years. The lawn to the right was not an option, for legal reasons, and the customer STILL wanted solar,
so we gave it to him.

 

[12VoltInstalls]

boom truck to set it all into place

And they still got shadows ? LOL

 

[sunshine_eggo]

And they still got shadows ? LOL

OUCH! Dang Bro!



I'd be willing to accept a little shading that early in the morning!

Trees? No problem! All it took was 3' diameter pipe with a 5/8" wall, 10 yards of concrete in a 12' deep hole, and my 30 ton boom truck to set it all into place. Nothing has moved in 15 years. The lawn to the right was not an option, for legal reasons, and the customer STILL wanted solar,
so we gave it to him.

Brute force approach. Very nice! I gather they're fairly well off.

 

[BoNeil]

So I have 4x 100w panels at my cabin only producing about 20-30 watts this winter. Is this normal? I only get 2-3 hours of indirect sun.

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