I posted a topic on NAWS expecting conformation of a solution to a senario I have the initial response indicates Im flawed in what I want to do. Which is OK as thats what I posted for but I think Im still on the money, guess its time to be humiliated but Im still sure my proposal is sound heres my NAWS post
Hi,
I dont see a problem with what I am proposing but would would like my peers opinions. I currently have two solar arrays going through two separate MPPT Charge Controllers. The maths is OK to put them through one controller. One array is tracked, single axis the other is fixed
Here is the maths
Fixed Array 12 x 200 wp panels VOC 40 volts currently wired in 6 strings of 2 panels at VOC 80v to a FM80 @ 48v
Single Axis Array 6 x 162 Wp Panels VOC 28.8 volts currently wired in 2 strings of 3 panels at VOC 86.4v to a Midnite Classic @ 48v
I have other plans for the Classic and can see no reason why I cant wire the six 162 wp panels one each in series to 2 of the 200wp panels.
Giving 6 strings of 3 panels each string being 40v + 40v + 28.8v = 108.8v VOC with a total watt peak of 3,373 . comfortably below the FM80 amp rating @ 48v
The distance between the tracked array and fixed array is 15 meters about 48 feet. The fixed array is only 3 meters from combiner to Controller So apart from 90 meters of 6mm cable its doable.
The fact that one panel in each string is tracked and the other two are fixed should make no troubles for the MPPT controller as the VMP and VOC will be
identical in each string.
Just hope Im not missing something
Nigel
Nigel, what is the Vmp and Imp of each array? I am not sure you will get very much production out of the 2 array, in total, as the FM's MPPT sweep function (assuming it is the same as MX) will probably pick one array or the others MPP point and run both arrays at that optimum(sub-optimum?) mpp point.
Does that make sense?
Eric
Seat of the pants guess is it is better to leave them on separate controllers. You got an hour or two at sunrise and sunset where that tracking array is really going to do it's thing. Why cripple it by tying it to a fixed array?
Good point VF, there will probably only be increased output when both arrays are 'pointed' in the same direction (bearing), most likely mid day, so there might be a gain at that time if both arrays had the same MPP....what are the odds?
Don't do this!!!
The smaller module will have a lower current output. When you put it in series with a higher output panel, all that happens is the higher output panels get drug down to the level of the smaller one. You will effectively made all of your modules 162 watts. You just threw away 456 watts of your array. The other problem is that one array is fixed and one is not. You need to have them both fixed. If you want the most out of your solar, use the Classic. It will put more power into your batteries than the FM80.
Now what to do about your problem......
4 strings of 3 40V panels. That is 120VOC
4 of the 162W panels in series. That is 115.2VOC
You will not hook up the other two panels. This is the best I can come up with given the equipment at hand. The FM80 can also accommodate this arrangement.
Good luck,
Robin
Ok Thank you all for your answers, I have my answer leave alone :)
It was only that the classic was having an easy life playing around with about 20 amps of delivery. I lleave the fixed array on the FM80 and I have another tracker to put up same as the first which will accomodate 1200 to 1400 watts with new panels giving the New Classic 150 about 2400 watts to earn its keep with. Then I have the best Controller with the same amount of PV as the fixed array but on two single axis tracker units. Sounds Win Win to me, wheres the cement mixer. :'(
Nigel