diy solar

diy solar

Running 10 75W panels in parallel

waphals

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Feb 22, 2021
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I am working on a Ford Transit van conversion and have yet to install my solar panels. I've done a lot of designing to find the best configuration for my roof space which has 2 AC units and best option I've found would be to use (10) 75W panels. Am I dumb for making myself connect 10 panels together or should I just have less power and an easier time installing? The alternate options are either less watts total or rely on mixing panel sizes. I've done an energy audit and we could get away with less than 750W but we could also put the energy to use if we have it :)

My main question is which option would be best?
Option 1: (10) Newpowa 75 W Solar panels panels in parallel with a Victron 250 / 85 SCC
Option 2: 2 arrays of (5) Newpowa 75 W Solar panels panels in parallel with each array having its own Victron 100 / 50 SCC

With the 10 panels in an array I would only have one point of entry into the van.
With the 2 arrays of 5 panels I would need two points of entry, but I would also be able to start off with 5 panels and then add the second array down the road after living in the van for a bit. Two of the smaller SCC's are cheaper than the 1 SCC.

Additionally, would 8 awg wire work for both options if there is a 26 foot run from the farthest panel to the SCC? That alone might force me to do the second option.

1633369878167.png

Also for fun, here are all of my games of tetris I played with my roof. I was just playing around seeing how much I could cram into each iteration. The Rich 200W panels don't quite fit my roof rack which was the main reason towards not using that option.
1633371122942.png
 
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All of the below assumes a 12V battery bank.

Those panels have a Voc of 20.23V. 10 in parallel will still be 20.23V. Why would you want a 250V charge controller? Perhaps you meant putting 10 in series. That would be 202.3V. Then a 250V charge controller makes a lot more sense. Based on the Victron MPPT calculator you would be good with the 250/70 with 10 in series.

But shading would be a problem at 10S. Perhaps 5S2P would be a better option. Then you could use a single 150/70 charge controller. This option also makes it easy to start with 5 panels in 5S and then later add the 2nd set of 5S in parallel with the first. Still one entry into the roof with the single charge controller.

If you really do want 2 sets of 5 panels in parallel then that could also work with two 100/50 charge controllers. If you could find a 100/70 charge controller you could do 2S5P with one controller.
 
Thank you for the easy read, that really helped clear up a lot of my confusion. You're correct it's a 12V battery bank.

I wanted a 250V charge control because I thought that you had to compensate the total VOC which would be 202.3 - However, it appears I was incorrect and was using battery logic thinking series would be for if I had 24 or 48V.

Since the overall cost would be the same I think the single 150/70 controller would be the best option with the 5S2P configuration. From what I've seen, 8 awg wire would work even if I started with both of the sets - but due to the distance would I be safer going with 6awg?
 
The idea of parallel and series is the same for panels and batteries. Series you add voltage and keep the amps the same. Parallel you add amps and keep the voltage the same. But whether your batteries are in any kind of series/parallel is completely independent of whether your panels are in some sort of series/parallel.

8AWG should be fine. Using the Blue Sea Systems wire size calculator app I plugged in 10A (the 75W panels at 2P will be just under 10A) at 52' (roundtrip length) with a 3% voltage drop. It gave an answer of 8AWG. For 2% voltage drop is suggested 6AWG.
 
Appreciate the help, I was just about to order everything until I triple checked everything... and apparently my dimensions were barely off and once everything added up I'm 3/4" over! Back to playing Tetris...
 
Ugh. I only have three panels on my trailer roof and I have 1/2" between each panel and my roof fans. I understand working with a tight fit.

Which is a good reminder. Make sure you allow for a 1/2" gap between panels for airflow.
 
Thanks for the airflow tip, I definitely would have not been able to make it work if I allowed that gap.

I'm thinking now about doing one of two options:
6 x 100W(19.83 Voc) and 3 x 30W(19.83 Voc) - All Newpowa products
2 x 240W(27.08 Voc) and 2 x 100W(24.3 Voc) - 240 is Newpowa and 100 are HQSTs since they are the closest voltage I found.

Would it be best to just go with the first option since the Voc is identical? Or is the 3 voltage difference in the second option not too big of a hindrance?
 
If you're using Z brackets to mount the panels, don't forget to take the added width or length of the bracket into account.
 
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