Changes applied (yellow-highlighted below). Click the pic
in this link for a higher rez version of this update (w/o the change highlights).
View attachment 10357
1. Up-ed the PV breakers from 25 to 32A.
2. "Buck" to "Boost" change.
3. Put the shunt sense wires where they're supposed to go.
4. Spec'd the shunts themselves.
A little more on shunt-spec'g that I've learned in the last 24 hrs:
For the 60A I can expect coming over the PV Shunt on sunny days, a
100A:100mV shunt would allow me to use
67% of SBMS's 0-90mV measuring range. A
100A:75mV would only use 50%.
(90mV/100mV)*100A = 90A
i.e. current on this shunt that would use 100% of that 90mV range is 90A
60A/90A = 67%
That # for a 100A:75mV shunt is only 50%. For a 90mV sensing range, that's the best I'm going to get out of any commercially available shunt (that I can find).
Same math applies for the 200A Load shunt. For my expected 120A max load, 100mV will allow me to use, again, 67% (vs 50% for the 75mV shunt). That the #s are the same is due to the fact that both rated current of the shunt and my expected max load are just coincidentally twice the #s for the PV shunt.
I can get both shunts
here and both in the same dimensions, which should make them easy to place/connect (& look nice too!).
Because these can get hot, especially if you're pushing their rated amp spec, I was curious how to derate them if you're starting off in a hot climate. I intend to spend not a little time in the desert. Death Valley is one of my favorite destinations.
Temperature Derating (source): If operated in ambient temps above +25°C, the maximum continuous current must be further derated from the 2/3 value previously noted.
To find the maximum permissible continuous current (Ie) at an elevated temperature (Te), one must first calculate the maximum allowable power dissipation (Pe) at Te, using the following formulas:
Pe = Pa x [1-(Te-25°C)/100°C]
Ie = SR(Pe/R)
Where:
SR = Square Root
Ie = Maximum permissible continuous current at elevated temperature Te
Pe = Maximum power dissipation at the elevated temperature Te
R = Shunt’s resistance
Pa = 0.667 x shunt’s rated power at 25°C ambient (W=V*A)
Te = Elevated temperature
My 100A shunt is derated to 77A. My 200A shunt is derated to 154A. So, good to go.