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How to wire together 36 250 watt solar panels -- no shade issues.

mawhelchel99

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Feb 7, 2022
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  • Rated Power: 250W
  • Open circuit voltage (VOC): 37.6 V
  • Max power voltage (VMP): 30.3 V
  • Short circuit current (ISC): 8.85 A
  • Max power current: 8.27 A
  • Power Tolerance 0/+3%
  • Maximum system voltage: 600V (UL)
  • Fuse Rating: 15 A
Here are the specs on each panel ... ideas how to wire this to save money on other equipment?
 
The short answer is to select a charge Controller or Inverter/Charger product with high maximum input, 500V to 600V, so as to maximize the number of panels that can be put in Series rather than Parallel. This saves on wiring and breakers in the combiner box. Based on the Voc stated above, I would say you will need a minimum of 3 strings of 12 panels. It depends on the actual Voc at the lowest temperature expected for your area and the Max allowable input to your charger device.
 
I am new to this ... can you tell me the amps and volts of each panel? I agree with you however putting it in series seems the best choice. Thanks
 
  • Rated Power: 250W This is the Factory/Standard Test Conditions (STC) output of the panel at 25 deg. C with 1,000Watt per sq. meter of simulated solar radiation.
In reality your normal output will usually be 70 to 85% of the rated value depending on panel azimuth, tilt and geographic location.
  • The Temp/Voltage coefficient for solar panels is approx . -0.3% per deg. C. Translation for every degree C below 25 the voltage will INCREASE by about 0.113V. At 0 C the Voc goes up to 40.4V. 37.6V + (25deg x 0.113V/deg) What is the coldest temp. expected in your area?
  • Open circuit voltage (VOC): 37.6 V. Need to calculate Voc for your coldest expected temp.
  • Max power voltage (VMP): 30.3 V Use this value as your operating voltage
  • Short circuit current (ISC): 8.85 A
  • Max power current: 8.27 A Use this value as your operating current
  • Power Tolerance 0/+3%
  • Maximum system voltage: 600V (UL)
  • Fuse Rating: 15 A
Here are the specs on each panel ... ideas how to wire this to save money on other equipment?
 
however putting it in series seems the best choice.
600v is.....well 600v! 550v above the upper limit for most DIYs looking for info regarding solar.
600v should be up on the roof, away from everyone, and connected to your house and mains by a qualified person who would be more interested in getting the commission from selling you new panels.

What I would do with 36 used panels. I only have 22 so far.
Connect 12 in // to a 24v 1000w heating element at the base of HWS that preheats the water going to your installed one. (or variation of this to offset the inefficiency of the double conversion with the PSU.)
The remaining 24- Convert to 12v and for $500 - 10x 30A PWMs(AliEX), 1500w inverter(local), 1500w PSU(AliEX), 2 sets of Supercaps(AliEx) and then use your time working out how to improve the cost effectiveness with batteries.
 
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ideas how to wire this to save money on other equipment?
What are you trying to do? Spin the meter backwards? Charge batteries? Are you off grid?

Wiring them together is easy. They all have connectors that connect to each other. You could make a deadly 37.6V x 36 = 1353V deathtrap with little effort. But if you want to put it to use, we gotta know the use case.
 
Unfortunately this is a ground mount, all I have is the panels so far. Ideas to keep it safe? Powering a house on grid. Batteries right now are way too expensive.
 
I am new to this ... can you tell me the amps and volts of each panel? I agree with you however putting it in series seems the best choice. Thanks
Voc = open circuit voltage. This is the voltage with no load. Tends to rise at low temperatures. Never never exceed the controller or solar inverter maximum input rating.
Vmp = voltage at maximum power
Isc = short circuit current in amps. This is the maximum amps.
Imp (current at maximum power) will be a bit less.

Fuse rating will be the fuse installed on each series string in the combiner box so that if there is a fault in one string the other parallel strings will be stopped from back feeing the fault at full power.
 
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