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Parallel or Series panels?

Nillerk

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Feb 6, 2021
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I have 5 175W panels and since it is an odd number, I understand they must all be wired the same way. Should I put them in series or parallel to go into a 150V/100A Victron Smartsolar controller?
 
I have 5 175W panels and since it is an odd number, I understand they must all be wired the same way. Should I put them in series or parallel to go into a 150V/100A Victron Smartsolar controller?
Add the Voc of all 5 panels to see if they can be connected in Series which would be a max of 150V plus considering that low temps will raise the Voc.
So what is the Voc?
 
NEC tables for -40 is a correction of 1.25, so, 119.5x1.25= 149.75... JUST squeezing in below the controller limit...
does it EVER get colder than -40?
 
Whew! I grew up in Newell SD, and it got bitterly cold there. Anybody that isn’t from the frigid north has no comprehension of -40cold... with wind chill on TOP! That usually means a windchill temp of -100!
 
Most panels give a more definite number for change in Voc versus temperature, so please share the part number. 1.25x nominal Voc is probably fine but may be pessimistic. I would double check and see if it comes in below 150V in series. If not, the next step up (for Victron MPPTs) is 250V which is a fair bit more expensive. Either way, 5 is a prime number so you should wire them in series.
 
I would go series. Get a controller with the proper rating. I think Midnight Solar has 200 and 250 rated. Morningstar goes to 600 if you plan to expand. Not sure all these work on 12v batteries.
 
Newbie here. Is the above logic correct? Aren't you assuming there will be maximum vertical sunshine while it is -40 degrees? It does not happen. Does it?
 
Newbie here. Is the above logic correct? Aren't you assuming there will be maximum vertical sunshine while it is -40 degrees? It does not happen. Does it?
Any light on a panel produces Voc even at sunrise on a cold morning.
You do not need max sun to produce rated voltage.
You do need maximum vertical sunshine to produce max Amps.
 
Newbie here. Is the above logic correct? Aren't you assuming there will be maximum vertical sunshine while it is -40 degrees? It does not happen. Does it?

My panels have a short circuit voltage of 21 volts, and a operating voltage of 18 volts. I see the higher voltage every morning as the sun starts to shine, and then the voltage will drop towards the 18 when the panels are producing max amps.

High voltage with little amps could harm the SCC. I would say that any cold day at -40 or below is a risk for exceeding the 149.XX volts, and not just waiting until high noon to make the measurement.
 
My panels have a short circuit voltage of 21 volts, and a operating voltage of 18 volts. I see the higher voltage every morning as the sun starts to shine, and then the voltage will drop towards the 18 when the panels are producing max amps.

High voltage with little amps could harm the SCC. I would say that any cold day at -40 or below is a risk for exceeding the 149.XX volts, and not just waiting until high noon to make the measurement.
Open circuit of 21, not short circuit...
 
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