Greetings!
Planning a DC coupled system with 30 panels Solarwatt classic AM 2.0 black (or similar). System voltage 48V. 3x Multiplus II 3 phase. 3x LIONTRON LX48-100
Situation: 18 panels facing almost exactly south, each 6 facing east/west on a big dormer. Roof pitch is 45 degrees for all panels. Panels on the east side will slowly get more and more sun in the early morning when shadow of the main roof will disappear. Panels on the west side of the dormer will get more and more shadow from the neighbor´s house (semidetached, slightly shifted to south) and his dormer beginning in the mid afternoon. Same for the most west panels on the main roof facing south.
Option 1: 2x mppt 150/85 with each 3s5p
Option 2: 1x mppt 250/100 with 6s3p and 1x mppt 250/70 with 6s2p
Each panel on every single string will face the same direction. With the arrangement of the strings I tried that each module of a string will have the "same amount of shadow" as good as possible.
Advantage of opt. 1 (more parallel): The smaller strings still deliver current when shaded, while a "more series" connection will tend to shut them down by lowering the voltage and activating the bypass diodes. IMHO this will increase the performance.
Disadvantage(s) of opt. 1: a) Possibility of a quite high back current if one string is partly shaded which probably will blow the string fuse quite often. b) If the mppt lowers the voltage more strings are affected, voltage steps from MPP to MPP will be quite crude.
Especially the Cons depend highly on the behavior of the mppts. This is why I would like to ask, 1) If the mppts can handle both options equally well. And 2) If my assumption of the Pro is right or can opt. 2 be equally efficient with the above mentioned circumstances?
Does this eventually depend on the amount of bypass diodes (3) in each panel ? Do I need panel optimizers at last?
Any comments on this welcome. Especially from the victron staff with deeper insight in the mppt algorithms.
I tried to describe the (IMHO) relevant points as good as possible, but English is not my mother tongue. If something is not understood, precise or missing, don´t hesitate to ask.
Thanx in advance and best regards from bavaria
Arnd
EDIT: tried to edit the links to the specs of the panels and battery modules, since they are not there, hope this time they will.
EDIT2: Nope, don´t know what went wrong....
