I have a new Maine Cat 38' that came with 6 solar panels. 4x140W and 2x120W. The builder arranged these panels with (2x140W+1x120W) in series with two such banks in parallel.
They are placed flat on the bridgedeck roof.
(If you're curious: The 4x140W are all arranged bow-to-stern in a line side-by-side, and the 2x120W are arranged laterally amidships. I *believe* the three panels to port are in series together, and the three panels to starboard form the second series bank, the two banks combined in parallel. )
While I'm docked or at anchor, I keep the boom oriented for minimal shading (usually to one side, and maybe for 1-3 hours straight down the middle).
I've noticed things like moving the boom to remove shading from a 120W panel results in more than a 120W increase in wattage.
I've *heard* that mixing panels (wattage) can result in limiting the utility of the bigger panels, but at the moment, I'm playing the hand I'm dealt.
- At anchor, I have some control over shading. When the sun is positioned favorably, all 6 panels are in the sun (there might be slight/small shadows from the boat's rigging). Most of the day I can get 5 in the sun (with a 120W panel all or partially shaded).
- At sail, I have minimal control over the shading (aside from choosing a tack based on shading, but that's usually secondary to navigational reasons for choosing a tack).
It would seem to me if all the panels could be wired separately into a single box, that box could make the decision as to the best way to combine the panels for peak voltage. At present, however, the panels are wired via terminal blocks with a single pair of wires coming into the MPPT.
The micro-manager in me wonders:
Would it make sense to have the wires come into a bank of switches such that I could arrange the panels based on present need into the best arrangement of series/parallel/off (per-panel) before the wires enter the MPPT? (Leaving them in a default configuration when I leave the boat or do not feel like micro-managing)
The panels run into a Victron 150/35 MPPT. The output is a 48V Lithium Victron battery bank (comprised of 2x24V in series).
Is there anything I can do to improve what I get?
(I see 250-350W in the sun, the lower end when a single panel is covered, and closer to 140W when two panels are covered. When the sun is overhead and the panels appear to be lit, the wattage always seems disappointing.)