The attached image describes the system I'm adding to my RV. I've used numerous free calculators on the internet and have not been able to come up with a definite, and repeatable answer.
I can't imagine I'll be camping in temperatures below-20F.
asked
MPPT Sizing
The maths is pretty straight forward.
Temp deviation from STC (25c) X Temp coefficient = % deviation from Voc
-54 X -0.30 = 16.2%
String Voc X above deviation = string voltage at -29c (-20f)
87.6 X 1.162 = 101.8v
You could use the Victron online MPPT calculator.
The Victron calculator suggests a 150/85 but I would personally go for a larger 150/100 as you might find the smaller model reduces your max power output (assuming 12 volts).
