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Old 03-14-2022, 07:51 PM   #1
Winemaker
 
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What's going on!?

OK solar experts out there... The numbers I see from my new system are unexpected...

Here is what I installed:
4 Renogy (HQST) 100W panels in series parallel (all wired correctly I hope).

See photos for the individual panel info and output with two of the panels in full sun and two partially shaded by the AC.

Why are the amps so low? I would have expected closer to 10 amps.

Any feedback or questions about the install would be great!
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Old 03-14-2022, 08:07 PM   #2
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36.75/13.34=2.75x3.4=9.36?
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Old 03-14-2022, 08:35 PM   #3
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Several factors:

1. Sun angle seems very low. Panels only (if ever) put out maximum power when the sun strikes the panels at a right angle. At low angles output is substantially diminished.

2. Battery appears to be getting charged more by converter than the solar panels. As charge approaches full the charge controller will reduce output.

3. If you want to see what the panels can do, turn off the converter, discharge the batteries, and see what the output is when sun is overhead.
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Old 03-14-2022, 09:02 PM   #4
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Quote:
Originally Posted by ITSNO60 View Post
36.75/13.34=2.75x3.4=9.36?
Can you expand on this formula? Why do you have a question mark at the end?

Watts Law says: 126W = 36.75V x 3.4A (124.95W) and 13.34V x 9.40A (125.4W)

Maybe I am just not understanding the difference be the info in the "Solar" area and the "Battery" area of the display.
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Old 03-14-2022, 09:13 PM   #5
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Quote:
Originally Posted by Al and Missy View Post
Several factors:

1. Sun angle seems very low. Panels only (if ever) put out maximum power when the sun strikes the panels at a right angle. At low angles output is substantially diminished.

2. Battery appears to be getting charged more by converter than the solar panels. As charge approaches full the charge controller will reduce output.

3. If you want to see what the panels can do, turn off the converter, discharge the batteries, and see what the output is when sun is overhead.
Thanks for your reply!

Answer 1 - Photo of roof was not at the time the info was captured from Victron app. The data was from closer to mid-day today. (was from the day when I had just finished installing them)

Answer 2 - The AS was not plugged in so my understanding is that the charger would not be active and all power would be coming from the solar panels and the MPPT. (Am I missing something/ misunderstanding what you mean by "converter"?)

Answer 3 - totally agree I should try to get all panels into the sun at "high noon" and see what numbers I get then. Hard to evaluate when only two panels are facing the sun.
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Old 03-14-2022, 09:59 PM   #6
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I presume the panels on the same side are the ones wired in series. If so then 3.4A for the one pair producing current at reduced capacity makes sense. The shaded pair will not be appreciably contributing. You will see output diminish considerably as the incident angle becomes more shallow. To get the 10A you are hoping for you will need full sun directly overhead.

For the math: the panels in series will have the same current while their voltage is added together. In the parallel arrangement the current is added while the voltage is the same.
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Old 03-14-2022, 10:01 PM   #7
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If it's truly series parallel, you will lose power on both series panels if one is shaded. I have (4) 100W AM solar panels all in parallel. Lower voltage from the panels but less affected by a single panel being in the shade. Also, you are getting close to 10 amps into your batteries according to the app.
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Old 03-14-2022, 10:02 PM   #8
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Quote:
Originally Posted by Winemaker View Post
Maybe I am just not understanding the difference be the info in the "Solar" area and the "Battery" area of the display.
Think of the Solar data as the input to the charge controller (from the panels) while the Battery data is the output from the controller (to the batteries).
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Old 03-14-2022, 11:27 PM   #9
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Winemaker, first off, I have 4 100w Zamp panels on my Globetrotter's roof and I also happen to live in Santa Rosa so we should have had similar sun exposure around mid-day today, which is when you say you took your reading.

I happened to check my Victron app around that same time and I was getting 260w of solar output, yet you are showing only 126w. I suppose there could be some variation in cloud cover at our specific locations, or in the orientation of our trailers, but it was generally pretty sunny here today and, given that, 126w seems low for mid-day. Are you sure all of your panels are producing?
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Old 03-15-2022, 05:39 AM   #10
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Shade one Square 1/36th of a panel

Here is a video from Gone with The Wynns showing the impact of shading just one square, in other words one 36th of one panel. and the dramatic impact.



Winemaker states the photo was not taken at time of testing, but notice the air conditioner partially shading one portion of one panel.

The take away from the video: covering One Square (1/36th of a panel) just about shuts down that panel, and when panels are in series, coving one square can have as much as a 90% reduction or more in the total panels output.
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Old 03-15-2022, 06:18 AM   #11
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Quote:
Originally Posted by GeeSag View Post
Here is a video from Gone with The Wynns showing the impact of shading just one square, in other words one 36th of one panel. and the dramatic impact.







Winemaker states the photo was not taken at time of testing, but notice the air conditioner partially shading one portion of one panel.



The take away from the video: covering One Square (1/36th of a panel) just about shuts down that panel, and when panels are in series, coving one square can have as much as a 90% reduction or more in the total panels output.
That video is from five years ago. Does it still apply? I've read that newer panels are made differently and not as susceptible to partial shading. Maybe someone in the know has more current information.
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Old 03-15-2022, 08:03 AM   #12
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Quote:
Originally Posted by Winemaker View Post
Can you expand on this formula? Why do you have a question mark at the end?

Watts Law says: 126W = 36.75V x 3.4A (124.95W) and 13.34V x 9.40A (125.4W)

Maybe I am just not understanding the difference be the info in the "Solar" area and the "Battery" area of the display.
Sorry I was in a bit of a rush last night. I was trying to show that the power from the panels into the controller was the same going in as coming out on the other side by multiplying the solar current by the same amount I divided the solar voltage by to arrive at the voltage coming out of the controller. In other words, amps x volts = watts, change one and you have to change the other by the same factor, so at 9.36 or 9.4 you are getting close to what you expected, the watts are basically the same on both sides just like you show in your watts calculation above. But I think you already understand the math, I think it's just a matter of understanding what the display is saying like you said.
OutdoorIdaho said it in fewer words in post #8. I think a lot of responders are thinking you are saying you are expecting the panels to be putting out more watts but if I read your post carefully it seems to just be the display issue that you are questioning? If not, and it is indeed the solar output watts you are questioning please disregard everything I said
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Old 03-15-2022, 03:16 PM   #13
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Really interesting video!
I am a bit shocked at how much a little shading can do. Definitely glad that everything is not in series. Will have to keep watching my results and the amount of shading at any given point.
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Old 03-15-2022, 03:24 PM   #14
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Quote:
Originally Posted by mikeinca View Post
Winemaker, first off, I have 4 100w Zamp panels on my Globetrotter's roof and I also happen to live in Santa Rosa so we should have had similar sun exposure around mid-day today, which is when you say you took your reading.

I happened to check my Victron app around that same time and I was getting 260w of solar output, yet you are showing only 126w. I suppose there could be some variation in cloud cover at our specific locations, or in the orientation of our trailers, but it was generally pretty sunny here today and, given that, 126w seems low for mid-day. Are you sure all of your panels are producing?
Nice to meet a fellow Santa Rosa Airstreamer!
I do think it's shading that is the dominant player in my lower watt reading. Two of the panels are facing almost North and get some amount shade from the air conditioner all day this time of year.

I will definitely check each panel to make sure all is working.

I have noticed that when I add the portable panels (200W Renogy) into the mix by plugging them into the front port, the whole output picture changes. I'll have to document that situation in another post.

This has been much more of a learning cure than I had expected.

Thanks all!
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Old 03-16-2022, 05:56 AM   #15
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How easy to bypass one for testing?

Winemaker:
How easy would it be to bypass the one getting the shade using longer cables with connectors to test to see if the one panel removed from series how much your power goes up?
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Old 03-17-2022, 07:40 PM   #16
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I'll definitely have to play around. I have plenty of connectors and wire I could use to make cables to bypass individual panels.

I also need to document the changes in Watts and Amps that happen when I connect the suitcase solar.

My gut says that the shaded panels are essentially off and I'm seeing just the power from the winter sun hitting the sun facing panels (200W).

Stay tuned...
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Old 03-17-2022, 08:49 PM   #17
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Solar directionality

Having lived off grid for 20 years I can tell you directionality of panels is EXTREMELY IMPORTANT.
I ordered a new Basecamp which I originally ordered with their solar system installed but flat installation of panels on the roof is not the best way to use solar panels.
I canceled that part of my build.
I adjust my portable zamp obsidian portable panels to follow the sun. If you don't adjust your sun angles efficiency can and will go down dramatically.
I adjust my angles with the equinox
December 21:45 degree angle
June 21:almost flat.
Rule of thumb:latitude +15 degrees at fall equinox
. latitude -15 degrees at spring equinox
Be mindful of the fact also that the higher the ambient temp the less efficient the panels become.
Solar panels love colder weather!
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Old 03-18-2022, 06:59 PM   #18
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Having lived off grid for 20 years I can tell you directionality of panels is EXTREMELY IMPORTANT.
First of all... 20 years off grid! I have to say I'm a bit jealous.

I can see how critical the angle would be for the power generation.
What I feel is that the 400W on the roof will act as maintainer and replace a bit of the power used while boondocking but that in order to truly recharge and extend my ability to draw from the batteries I will need to hook up the suitcase solar and make sure the angle is correct to maximize the power generation.

The Victron MPPT I installed has two separate inputs with MC4 connections. I have one wired to the rooftop solar and the other to the port the suitcase plugs into.

More testing will be needed to find a more accurate understanding of the power generation in each location/setup.
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Old 03-20-2022, 09:58 AM   #19
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Hi

Ok, the original picture shows the unit putting 10A into a battery at 13.36V. Assuming it's a lead acid battery, that is pretty close to a full charge.

The picture also shows 36V coming out of series panels. With anything close to full sun, that number should be 40V. If you climb up a ladder, I suspect you will see some shading.

To get "max power" out of panels at this time of year / most places in the US, you need to tilt them towards the sun. Is that a 20 degree tip or something over 60 degrees? Very much a that depends sort of thing. Flat mounted panels on the top of an RV are always a compromise in this regard.

In terms of shading and a lot of YouTube videos, what most are showing are poorly made controllers rather than anything about the panels. You MPPT with high voltage panels will perform very differently than what the typical YouTuber is showing.

So lots of twists and turns ....

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Old 03-20-2022, 10:38 AM   #20
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Hi Winemaker. I'm just south of you in Petaluma. What Bob said: "To get "max power" out of panels at this time of year / most places in the US, you need to tilt them towards the sun. Is that a 20 degree tip or something over 60 degrees? Very much a that depends sort of thing. Flat mounted panels on the top of an RV are always a compromise in this regard."

When I camp on the coast at Wrights Beach north of Bodega Bay for a week in December I use my AM Solar tilt legs to tilt my panels to get enough power for the week. - Brad
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