I have a Classic 200 hooked to (eight) BP SX170B panels. Four of the panels are at 60 ft away one way, and the other four are 90 ft away. Wiring is all #6 and the further away array is connected to a combiner at the closer array, where all power travels down a single run of #6 to the charge controller.
Panels are Vmp 35.4, Imp 4.8A, Voc 44.2. Minimum winter temperature -10F
Current configuration is 48V panel voltage into 24V battery. Will I gain or lose anything by wiring panels for 96V?
Volvo
So you have 2 panels in series now? Seems 90 ft is ok with #6 but I would have to run the numbers.
Ryan
your numbers don't look too bad right now. the worst case is a bit over 2% v drop if i read this to be 30ft from the farthest pv array to the closer pv array where it's combined and then another 60ft to the cc. running at double the voltage will really throw the v drop percentage low. about .5%. being this is the 200 model you don't need to worry about the arrays throwing it into hypervoc as the voc would be 141.6v at 25 degrees c.
now the improved v drop losses sound great doing this, but the efficiency on the classic going from a much higher input to output voltage ratio is not as good and maybe ryan would know if it would be a wash or worse for the efficiency losses.
This is actually a tough question.
Knee jerk is I'd much rather lose 2% of 96v than 2% of 48v, but the source/destination v losses might make it a wash. Tricky.
If the Voltage Drop is 2% or less now I would leave it alone. The extra heat and what not in the Classic would be about a wash for the very little gain you would get by going a higher voltage.
Ryan
Thanks!
I'm about to add a third array at 120 ft. So I will have three arrays at 60-90-120 ft all daisy chained together with #6.
I bought a 200 thinking I would run these three arrays at 96V nominal. Now I'm wondering...
Should I leave panel voltage at 48V with this new configuration? I figure I'm pretty close to the amp limit on the 200, but in real world conditions, likely won't bump up against it often.
2040W of panels. my options are..
Two panels in series, six parallel strings, Classic 200
Four panels in series, three parallel strings, Classic 200
Two panels in series, six parallel strings Classic 150
Four panels in series, three parallel strings, Classic 150 ( I think I'm over to the voltage limit here with Voc of 44.2V/panel though)
I cannot wire for three panels in series because of my tracking arrangement.
Ideas?
Well if you are adding a 3rd array I think going 4 in series makes sense.
Ryan
i think you may want to upgrade the first 60ft run of wire as you are not only adding a longer run, but also more current which will add to what's there already. you will have a much higher v drop and percentage with this additional link in the daisy chain. daisy chaining also isn't the best thing to do, but if you do it, each successive stage after the farthest array should be upgraded as far as the wiring goes and the size depends on many factors. if you haven't had the chance to, please play around with a v drop calculator. i have one listed in my sigline on naws and bb has also found a decent one.
btw, any more than the 2 arrays you presently have paralleled will need to have fusing/circuit breakers.
Thanks for all the help!
I have not played with that V drop calculator yet, However my seat-of-the-pants calculations said if I moved to 96V array voltage when I added the third array, the current would drop by 1/2, so adding 33% more watts to the end would still keep me under 2% drop. Not looking forward to buying 120 ft of #4 :o
I have MNPV6 boxes with breakers in them on each pole right now and each series string has a breaker. I plan on doing that again with the third array.
VF, why so far between arrays?