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diy solar

Solar charge controller calculator

Curb71

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Sep 29, 2019
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I want to do a big upgrade to my little RV solar setup. I bought 4 Lion Energy UT1300s. Trying to figure how many panels my Renogy Rover 30A can handle or if I need to sell it and upgrade. Here's the panel specs. I don't understand what this calculator is asking for the Temp coeff & PV Module temp.
(click custom module)
 

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Below is a portion of the datasheet for your panel from http://support.newpowa.com/support/solutions/articles/63000148028-npa175s-12h
It is more complete than the label on the panel.
1606516348350.png
The output of the panel changes with temperature, so the calculator needs to know the temperature coefficient and the lowest operating temperature you expect so that it can calculate if you will go over the allowed input voltage of the charge controller.
 
Below is a portion of the datasheet for your panel from http://support.newpowa.com/support/solutions/articles/63000148028-npa175s-12h
It is more complete than the label on the panel.
View attachment 28739
The output of the panel changes with temperature, so the calculator needs to know the temperature coefficient and the lowest operating temperature you expect so that it can calculate if you will go over the allowed input voltage of the charge controller.
Thank you. I wasn't able to find that online.
I entered -80 (or -90?) on the calculator for the V temp coeff and that's apparently incorrect because all recommended SCCs disappear from the list once I do that.
Does PV Module temperature [°C]: just mean to enter the lowest and highest possible daytime temp where the solar panels will be?
 
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They have the voltage temperature coefficient listed in mv/°C on your panel, and the calculator wants it in %/°C. If you click the little calculator icon by that blank in the calculator, it will pop up a conversion tool. Just don't forget to enter the minus sign.

Otherwise it converts to -0.3954%/°C (the calculator rounds it to -0.4)
 
They have the voltage temperature coefficient listed in mv/°C on your panel, and the calculator wants it in %/°C. If you click the little calculator icon by that blank in the calculator, it will pop up a conversion tool. Just don't forget to enter the minus sign.

Otherwise it converts to -0.3954%/°C (the calculator rounds it to -0.4)
Thank you again. I guess I'll be upgrading my SCC.
 
Yeah, it is important to get this correct. I've seen a couple examples on youtube where people have had their solar charge controllers refuse to turn on in the winter until the sun had warmed the panels up. Worst case scenario is that the charge controller gets destroyed.
 
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