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Small Cabin Forum / Off-Grid Living / If you had 2x100w panels sitting around
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gcrank1
Member
# Posted: 10 Feb 2021 11:28 - Edited by: gcrank1
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Ive a pair of 12v not in service (They do match my other 4 panels, 2 in series for 2 banks in parallel. I could tie them in with that array as another 2s for 3 banks of 2s in 3 parallel) but Im wondering about putting them together as a stand alone 'somewhat portable' 12v ground stand. This way I can optimize positioning in my compromised solar exposure and have the scc and battery being charged right at the array, rotating into use as needed.
Each panel:
102w
Rated about 18vmp
Peak about 21voc
Isc (iirc) 7.2a
Paired in parallel is peak (never realized) 21v/14a
Paired in series would be peak 42v/7a
I will have to get a new scc for either if I make em stand alone (my current MPPT can handle them if added).
So, should I go PWM (for parallel, 12v only) or a new, smaller cap. MPPT (for series @ 24v/to 12v thru scc)?
Objective: to get the best out of the array (isnt that what we all wish for, lol)

Brettny
Member
# Posted: 10 Feb 2021 13:47
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I have 4 235w full sized pannels sitting in my shed right now. They also match my current pair in use. If my little roof would fit even one more pannel I would use it but it cant.
I say put then in your current array. Mppt is almost always the best choice. At least you can either use series or parallel with mppt.

gcrank1
Member
# Posted: 11 Feb 2021 18:14 - Edited by: gcrank1
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Good point on the mppt scc can do both.
Has anybody here run a couple of panels like these on pwm and mppt so I can see real world amps numbers?

Brettny
Member
# Posted: 12 Feb 2021 08:25
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I know on PWM anything over the charging voltage is lost. Mppt anything over the charging voltage is turned into more amps.

paulz
Member
# Posted: 12 Feb 2021 09:55 - Edited by: paulz
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I have a couple of spare panels at my city house (lots of sun) that I've done a little testing with, using both PWM and MPPT CCs. I don't have numbers, too many variables in batteries, hours of sun etc. but I have become convinced in the advantage of MPPT such that I would never spend any money on a PWM.

I also still have a couple of the 130w HF PWM systems hooked up at the cabin, neither of them seem to be doing much good, and they are advertised as low sun panels.

ICC
Member
# Posted: 12 Feb 2021 10:55
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Quoting: gcrank1
Has anybody here run a couple of panels like these on pwm and mppt so I can see real world amps numbers?

No. But with a high voltage MPPT controller and enough panels, we have seen 10-12 watts from a full moon. You won't get that from PWM.

Brettny
Member
# Posted: 12 Feb 2021 11:18
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I have a mppt also. I had about 1/2in of snow on the pannels last trip. I cleaned them off and gained 0.1a. I wont do that again. Not sure how PWM would react to snow on the pannels.

gcrank1
Member
# Posted: 12 Feb 2021 11:50 - Edited by: gcrank1
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Well, that cinches it. Just like NO more MSW inverters for me, NO more PWM cc, its all MPPT from here on out.
My conclusion, my best use of these 2 panels is to series them for 24v and add to my array so it is the full 6 at 2s/3p on the Blue Sky 50 mppt scc.
That array and the powerhouse needs to become better located, right now my solar exposure is dead by noon. If I go east by 50ish yards it will be way better. It will also be more exposed, both to us and others looking up the driveway. Id like to just have a 'doghouse' for the scc, bat-bank and inverter but fear I would show up one day and find it all gone. I figure it would take a couple guys with a pickup truck less than an hour to disappear it all. My powerhouse/toolshed is a hard to move 8x12 ice shanty. With all the fancy stuff inside it is out of sight and pretty secure. Doesnt look bad either, homebuilt version of a 1930s travel trailer.
It would make a nice micro-cabin on its own; maybe someday.

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