actually it an airstream travel trailer and with 3 195 watt 24 v panels the voltage is below the 150v rating on the 45amp MPPT controller.
when I put a low temp of 19°F in the string calculator, "they" came up with voltage at 50.52vdc which is over by 1.56volts when connected in series..
Now I can tell you it will be a cold day in hell before I am in 19 degrees for any length of time and that would be early morning with LOW sun angle so the voltage will most likely NEVER exceed 150 volts.
My main purpose of this post was not to find the cheapest way to do this install. I want to do the best with a budget in mind and using the most cost effective products of quality, like morningstar products.
I know there are other good lower cost products but when you read post of folks that do a lot of solar like my friend handy bob solar, you learn what is a good quality product at a good price and will do the best job for your batteries.
In reading the morningstar white paper on the difference between MPPT PWM on lower watts and voltage system the PWM is the best choice. On higher voltage systems the MPPT will out perform more often with lower sun angles.
I do understand about the wire size and estimate only needing less than 10 ga which is most of the MC4 stuff. so the loss will be less than 1% which i can live with.
is this the best system maybe maybe not. but it seems like it might work for me.
