My RV setup - shade is killing me!

[xiaowudao]

Hey all! Hoping to get some advice on how I should proceed with my RV solar setup.

My setup is 3 x 170AH lithium batteries from Renogy, as well as a 3000W inverter. On my roof I currently have 2 x 175W panels and 2 x 100w panels (both renogy flexible). These panels are currently wired in a series-parallel configuration as outlined in this youtube video at 7:00:

. According to this I should be getting 100% output from these panels under best conditions right? All panels are going to the same MPPT charge controller.

However, I've noticed that because of other objects on my RV roof such as the air conditioner and whatnot, it is pretty typical for at least one of the panels to have a small bit of shade on it. Due to this I've noticed that most of the time I get less than half of output from all the panels.

Going forward, what would be my best option? should I have just done 4 x 100w panels in parallel? I unfortunately can't fit 4 x 175w panels, there is only room for 2 of those total.

Thanks in advance for taking the time!

 

[WYtreasure]

Welcome to the show.

Can you elevate or relocate the shaded panels? Maybe turn the RV a bit.

 

[chrisski]

Yes for situations like yours, all four in parallel will be best. Moving may produce better results, but weigh the cost of drilling the roof again.

I planned my placement to park a certain direction in the sun, but things like air conditioners do shade.

==========
I honestly recommend a second SCC with a couple of panels on 25’ extension so you can move and point at the sun. I have much better results with half the wattage on portable panels than I do with twice the wattage flat on the roof.

I use these panels:
https://www.walmart.com/ip/Lion-Ene...anel-Foldable-Portable-with-Handles/422072307
I can’t build a similar panel for less money from scratch.
================
Here is a thread I did on shading:

Parallel Panels and Shading versus Series Parallel

I tested some panels for output today when shaded. 2 Panels in Parallel (36 Cells Per Panel) -One panels with only 2 cells shaded 26% Reduction in Wattage -One Panel 50% shaded 54% Reduction in Wattage 3 Panels in Series (33 Cells Per Panel) -One panel Two cells Shaded 33%-50% Reduction in...

diysolarforum.com

======
I tested some panels for output when shaded.

2 Panels in Parallel (36 Cells Per Panel)
-One panels with only 2 cells shaded 26% Reduction in Wattage
-One Panel 50% shaded 54% Reduction in Wattage

3 Panels in Series (33 Cells Per Panel)
-One panel Two cells Shaded 33%-50% Reduction in Wattage
-One Panel 50% Shaded 69% Reduction in Wattage
-One Panel 70% Shaded 88% Reduction in Wattage

 

[fafrd]

Hey all! Hoping to get some advice on how I should proceed with my RV solar setup.

My setup is 3 x 170AH lithium batteries from Renogy, as well as a 3000W inverter. On my roof I currently have 2 x 175W panels and 2 x 100w panels (both renogy flexible). These panels are currently wired in a series-parallel configuration as outlined in this youtube video at 7:00:

. According to this I should be getting 100% output from these panels under best conditions right? All panels are going to the same MPPT charge controller.

However, I've noticed that because of other objects on my RV roof such as the air conditioner and whatnot, it is pretty typical for at least one of the panels to have a small bit of shade on it. Due to this I've noticed that most of the time I get less than half of output from all the panels.

Going forward, what would be my best option? should I have just done 4 x 100w panels in parallel? I unfortunately can't fit 4 x 175w panels, there is only room for 2 of those total.

Thanks in advance for taking the time!

I have some serious shading issues which I addressed by using a parallel (1S) array of half-cut panels.

Any half panel with any shading will not produce but each unshaded half-panel contributes a full 50% of maximum possible output (based on time of day, any haze, etc…).

So with 4 half-cut panels wired up in parallel, some shading on one half of one panel, output would be 87.5% of what it would be with no shading at all…

With a 2S3P array controlled by a single MPPT, shading on 1/3 of one half panel should activate a single bypass diode and drop voltage and power to provide ~83% output but if that shading impacts 2/3 of one half panel (meaning any cells in 2 neighboring column pairs), bypass diodes being activated for those two columns would drop voltage and output to 67%.

And if shading impacts any cells in all three 1/3 sections of any half-panel, bypassing that entire panel would drop voltage and power below 50%, so instead, that entire 2S string will be choked off with full Vmp while the other 2S string provides it’s full power output (so 50% of unshaded power).

2S2P strings are the worst configuration of 4 panels when dealing with partial shading issues…

4S1P is best if you do not have half-cut panels followed by 1S4P.

While a 1S4P array half-cut panels will match or outperform a 4S1P array of non-halfcut panels in most every partial shading situation followed by a 4S1P array of half cut panels which will perform pretty much like non-halfcut panels when in a 1P string.

 

[fafrd]

Yes for situations like yours, all four in parallel will be best. Moving may produce better results, but weigh the cost of drilling the roof again.

I planned my placement to park a certain direction in the sun, but things like air conditioners do shade.

==========
I honestly recommend a second SCC with a couple of panels on 25’ extension so you can move and point at the sun. I have much better results with half the wattage on portable panels than I do with twice the wattage flat on the roof.

I use these panels:
https://www.walmart.com/ip/Lion-Ene...anel-Foldable-Portable-with-Handles/422072307
I can’t build a similar panel for less money from scratch.
================
Here is a thread I did on shading:

Parallel Panels and Shading versus Series Parallel

I tested some panels for output today when shaded. 2 Panels in Parallel (36 Cells Per Panel) -One panels with only 2 cells shaded 26% Reduction in Wattage -One Panel 50% shaded 54% Reduction in Wattage 3 Panels in Series (33 Cells Per Panel) -One panel Two cells Shaded 33%-50% Reduction in...

diysolarforum.com

======
I tested some panels for output when shaded.

2 Panels in Parallel (36 Cells Per Panel)
-One panels with only 2 cells shaded 26% Reduction in Wattage
-One Panel 50% shaded 54% Reduction in Wattage

3 Panels in Series (33 Cells Per Panel)
-One panel Two cells Shaded 33%-50% Reduction in Wattage
-One Panel 50% Shaded 69% Reduction in Wattage
-One Panel 70% Shaded 88% Reduction in Wattage

It’s not really what % of the panel that is shaded that matters. It is first and foremost: what % of any individual ]b]cell [/b]within a panel that is shaded.

Any cell totally shaded will choke off all output if the bypass diode of the 1/3 panel (pair of adjacent cell columns it resides in) is not activated by the MPPT (at which point output from that panel will increase to ~100% current at ~67% voltage, which will also impact any parallel panels/strings).

After the worst-case individual cell shading, it is next how many other 1/3 sections have any partial shading and what % is shaded of the most-shaded cells in those other partially-shaded 1/3 panels.

A panel with only a single cell 100% shaded in all 3 1/3 panels (5% shading for a 120-cell panel) will have close to 0% output, while a panel where every one of the 120 cells is 50% shaded (50% shading) will deliver 50% output.

The worst-shaded individual cell within any 1/3 panel (pair of adjacent columns) will limit the output of the entire panel unless the entire 1/3 panel gets bypassed by the bypass diode as controlled by the MPPT. If any 1/3 panel has been bypassed, output of the remaining 2/3 panel will be limited by the next-most-shaded-cell within those 4 columns, etc…

All of the above is for standard 60 or 72 cell panels (non-half cut) with 3 bypass diodes organized to bypass a pair of adjacent columns.

Half cut panels are essentially a mini-1S2P array of half-panels (with shared bypass diodes), so any individual cell 100% shaded in either half-panel will reduce current output to 50% at full Vmp voltage (without activating any bypass diodes).