My 22.5 voc. 100 watt panels are ranging up to 24.4, or 97.6 with. 4 in series. Mppt max is 100v. Will this continue, or over the years will the voltage output decrease ?
22.5 VOC ranging to 24.4
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Is it especially cold and sunny in your area? That's getting too close for comfort. What is your nominal voltage? If 12 volt maybe you should go 2s x 2p.2.2kw Suntech mono, Classic 200, NEW Trace SW4024 -
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Your panel specification should give a coefficient of voltage rise per Centigrade degree which you can use to calculate the voltage for any temperature. Note carefully that during the night, with a clear sky, the panel temperature can go below the air temperature, and that low temp can carry over into the early morning when the sun hits the panels.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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What battery voltage are you using?
If you answer is anything other than 12 or 24 volts, reconfigure your panels for 2 x 2. If 48 volts you are SOL and cause damage on a cold morning. Generic Calculation is take the Controller Voc and divide by 1.25. You panel Voc should be less than that voltage. So if you have 100 volts / 12 volts = 80 volts. Your panel Voc is considerably higher than that. You panel Voc Spec = 22.5 volts riight? 4 x 22.5 = 90 volts or 10 volts to high. They would have to be 20 volts to use 4 in series to safely use them south of IH-40.MSEE, PEComment
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And if the generic calculation comes out bad (damaging voltage) you can try again using real winter temps and the coefficient off the panel specification, and then give yourself at least a 5% cushion.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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Spec : Temperature coefficient of Voc is - 0.30 %/Last edited by Brian53713; 01-08-2017, 02:03 AM.Comment
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But then, do you really ever see Voc. That would imply the controller fully turns off. Even rather minor currents drop the voltage dramatically. A MPPT with a 100V limit is a minimally designed controller to begin with.Comment
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Then again, what are you using to measure the voltage with, and can you vet the accuracy with something like a Fluke multimeter? Could very well be that your instrumentation is slightly off until verified with an accurate meter.
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Silly question. Every controller no matter what type it is sees Voc in the cold morning when the sun rises. That is why you have to derate. NEC method is 1.25 and is just fine if you live along the corridor or south of Interstate Highway 40. If you are like me, I wear suspenders and a belt, I use manufactures derate specs. Exceptions are Gulf coast states, high altitude, and where I live now in Panama. Hell in Panama no need to even bother.Last edited by Sunking; 01-08-2017, 01:20 PM.MSEE, PEComment
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I have disconnected one of the panels, so just 3 in series.. Is the fluke multimeter just a very trusty brand? Or can I use my cheap multimeter where the panels go into the mppt to see if it matches the voltage that the Bluetooth dongle app on the smartphone is showing me that scary 97.64 voltage .have seen once so far on a very cold, day like we're having now. Is one solution to just disconnect and use 3 panels during these extreme cold weather? Since I seem to get to float everyday no problem . Thank you in advance to all the trusted experts.My panels specifications
.Spec : Temperature coefficient of Voc is - 0.30 %/ , can one of the experts please explain what that temperature coefficient means please.Comment
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Take your Mother's advice and do not play with your Dongle, or anyone else's.Last edited by Sunking; 01-08-2017, 01:54 PM.MSEE, PEComment
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Spec : Temperature coefficient of Voc is - 0.30 %/Last edited by Brian53713; 01-08-2017, 03:12 PM.Comment
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