I am adding 2 additional panels to my current array. I have 6 Hyundai 250W panels, two strings, with 3 panels connected in series in each string. In Wyoming the temp. may go to -40 degrees (that temp is the same for both C and F, and it is on those days, you bring the brass monkeys inside.) By adding one additional panel to each series string, I will be in the realm of HyperVOC, which I would like to avoid. The array has room for the 2 additional panels, and I would like to upgrade the currently installed Classic 150. Can the circuit board of the 150 be replaced with a new circuit board for a Classic 200? Are there any other changes required, or are there other suggestions on how to do this? Thanks, Newman
you will need to give us more information, like battery bank V &, PV specs, number of days at -40 etc, and how long the -40 lasts... average DoD... enough for now
Sorry for the lack of info.. This is a 48 volt system. The -40 would most likely happen for only a few hours just around sunrise. Minus 20 is fairly common while minus 30 is rare, minus 40 may only occur once in 5 years. The PV array calculator on this web-site says the use of 4 panels is marginal. The panels are HYUNDAI HiS-S250MG Vmp 30.5, CURRENT Imp 8.20, Voc 37.5, CURRENT Isc8.70.. Replacing or rebuilding the Classic 150 may be more than is necessary..
Thanks, Newman
doing a quick mental calculation you are pretty close as their calculator shows.
Have you thought of getting a KID for the 2 extra panels, It would be a good match for 2 of those panels, at first glance... for a 48 V bank.
That looks like it would require another set of wires to run from the array to the charge controller which is located in the basement of the cabin. About 120 ft. Haven't figured out what is involved in swapping the circuit boards to make this one a Classic 200. I guess I could disconnect the 2 additional panels during the Winter.
If the -40 events are so rare and -30 not so often then I would not be too concerned as you have a Hypervoc of 150+48v. Ok the Classic does not produce power in Hypervoc but you would probably not be concerned as the temp will rise pretty quickly as sun comes up.
So 4 panels in series with mpv about 120v is good for the Classic 150 and you have plenty of Hypervoc headroom for the occasional really cold morning.
Changing to Classic 200 does not look necessary to me.
In any case I have never seen a Midnite Classic board (ex)change scheme to allow Classic model alteration. (is there such a scheme?)
The cost of a 200 lite is so low that it may be more economic to buy a 200 and sell the 150.
dgd
Or consider adding three more panels not two, to make 9 total in three strings...
Thank you for the in-site.
The array would require major re-welding to accommodate 3 panels.
I just asked a similar question, I had one string of (three) 230w panels and wanted to add another. Pushing 110V in Fairbanks, Alaska made Hypervoc a real problem in the winter.
Recommended solution, "bring your Volts down". I went with (two) string of (two panels) in series then parallel at the combiner box, down to 74.4V. I added the other panel, it only cost me another 40' of wire.
You could do similar and not have to change out the MN 150.
Newman,
There is more than swapping out the boards, the inductors are different. This would make it not likely worthwhile to try to upgrade your 150 to a 200. Better to sell the 150 and buy 200 than try that upgrade. There used to be a buy and sell solar somewhere on this board but I have not seen it in a while.
When looking at "24" volt panels you will find most with 60 cells but some others have 72 cells. You basically cannot mix the two kinds. I'm thinking that you have the 72 cell variety.
Rule of thumb. Panels is series must have the same current rating at max power.
Panels or strings of panels in parallel must have the same voltage within a percent
or two to maintain high efficiency.
I have strings of 55 watt mono 36 cell panels working well with strings of 280 watt poly 72 cell panels. The string voltage is within .8 volt so I got a good match and it works well. I also have some 60 cell panels I cannot use just right now due to incompatible voltages. And a dozen or so of the really antique Arco 50 watt 30 cell "self regulating" panels that I cannot use in a mixed array.
Several companies are producing the 72 cell panels including Suntech (poly crystal only) Epolly, and Canadian Sun.
Do your research, find panels with compatible voltages and stick with the c150. It's the best.
td