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Old 07-14-2023, 04:00 PM   #1
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Question Solar panel configuration question

I'm in the process of setting up my solar panels on my short bus, I'm using 4 panels , two side by side and front and back. I already figured out the best way to go is series and then parallel. My question is which way will I get the most from my system overall, series side to side and parallel front to back, or series front to back and parallel side to side. The panels are mounted to the roof which angles them jest a bit right and left. I'm trying to figure out in a 24 hour day which configuration will give me the most charge. Your thoughts on this? oh also in case it matters the panels are 24 volts 100 watts each.

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Old 07-14-2023, 04:18 PM   #2
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If you see yourself parking under cover in a way that any shading - if present - always falls on one particular portion of the bus, it might make a difference how you arrange them. Otherwise, I can't envision a scenario where it would matter. I'd be more concerned with how the arrangement impacted my wire runs (shorter being better).
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Old 07-14-2023, 04:48 PM   #3
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I arranged mine s2p3, with each side and the center being a string
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Old 07-14-2023, 04:53 PM   #4
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I arranged mine s2p3, with each side and the center being a string
And how is that working for you, any regrets?
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Old 07-14-2023, 05:50 PM   #5
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And how is that working for you, any regrets?
I dont have another configuration to compare, but it seems like it works great. No problems.
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Old 07-22-2023, 07:54 PM   #6
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The only real factor as mentioned above is shading. If one panel has shade on it, it's going to impact the string so do you think you'll be most likely to have shade down a side or across the bus? If you had the left and right side strung together and 3 inches of one entire side of the panels was shaded that would impact your solar more than if you isolated to two sides. Really, there's no way to do it wrong, I just try to get voltage as high as I can within the A/V limitations of the charge controller. For me that's 4 strings of 3 panels and makes the most sense to do 3 in a row on each side.
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Old 07-23-2023, 02:36 PM   #7
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The only real factor as mentioned above is shading. If one panel has shade on it, it's going to impact the string so do you think you'll be most likely to have shade down a side or across the bus? If you had the left and right side strung together and 3 inches of one entire side of the panels was shaded that would impact your solar more than if you isolated to two sides. Really, there's no way to do it wrong, I just try to get voltage as high as I can within the A/V limitations of the charge controller. For me that's 4 strings of 3 panels and makes the most sense to do 3 in a row on each side.
Just bear in mind that the more a MPPT charge controller has to step down the incoming voltage from the panels, the less efficient it is electrically, i.e.the more heat it is producing. Heat is the biggest killer of electronics. I know there are some theoretical benefits to having a greater step-down, but for me I would rather place less stress on my Morningstar TS-MPPT-60 charge controllers by limiting their voltage step-down to about 2:1.

If you have PWM charge controllers, a greater step-down ratio simply means that more of the panels' power is being wasted.

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Old 07-28-2023, 12:09 AM   #8
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Just bear in mind that the more a MPPT charge controller has to step down the incoming voltage from the panels, the less efficient it is electrically, i.e.the more heat it is producing. Heat is the biggest killer of electronics. I know there are some theoretical benefits to having a greater step-down, but for me I would rather place less stress on my Morningstar TS-MPPT-60 charge controllers by limiting their voltage step-down to about 2:1.

If you have PWM charge controllers, a greater step-down ratio simply means that more of the panels' power is being wasted.

John
I won't debate you on this but would say it wouldn't be on my list of things to even consider. Only because matching wattage on an MPPT isn't always easy, you're often over on amps or volts but still have room to add more watts if not for one of those issues.

You're talking about 1-2% which you can more than make up for with one additional panel. For some people, sure, maybe think about this all else being equal but often times with limited space and so on configuration is dictated by every other factor.
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Old 07-29-2023, 10:38 AM   #9
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Originally Posted by Brewmaster View Post
I'm in the process of setting up my solar panels on my short bus, I'm using 4 panels , two side by side and front and back. I already figured out the best way to go is series and then parallel. My question is which way will I get the most from my system overall, series side to side and parallel front to back, or series front to back and parallel side to side. The panels are mounted to the roof which angles them jest a bit right and left. I'm trying to figure out in a 24 hour day which configuration will give me the most charge. Your thoughts on this? oh also in case it matters the panels are 24 volts 100 watts each.
Honestly, I would put the strings in the front & back, and then run those string in parallel because I see myself being far more likely to park a bus with either the back or the front under some shade--eliminating one string or the other than I am to park the bus facing north/south and lose maybe an hour of cumulative charge time while the sun rises or falls because the angle is too steep to hit both panels in the opposite array. Regardless, I've found that I will typically figure out the power I'm getting to work with, and adapt my living constraints to be inside of that.
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Old 07-31-2023, 02:59 PM   #10
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If you really want to get OCD about things and we’re going with fixed mounts…
Assuming it’s a left-hand drive in the US, you would be parallel parking on the street in more spots with the right side of the bus closer to any off-street trees so you’d want more sky visibility on the left side of the roof.

Right??
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Old 08-01-2023, 08:06 AM   #11
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If you really want to get OCD about things and we’re going with fixed mounts…
Assuming it’s a left-hand drive in the US, you would be parallel parking on the street in more spots with the right side of the bus closer to any off-street trees so you’d want more sky visibility on the left side of the roof.

Right??
That's assuming that you're not changing directions; and that you live in a place where parallel parking is the norm. In Texas, we usually have real parking spots pretty much everywhere, and the only places you can normally find parallel parking is downtown by the courthouses, and outside of the nightlife district(s).

There are also plenty of places with major hills & minor mountains, and honestly who parallel parks anywhere but the East Coast and downtown in big cities? Maybe some kind of hill country.

I think it still makes sense to run the parallel front/back because you're far more likely to spend more time "parked" with either the front or the back covered.
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