How about this design for my boat? Do I really need 25mm2 from the MPPT to the battery bank? And why do the MPPT connections only accomodate for 6mm2?
asked
MPPT 75/15 - Setup of panel, MPPT and battery?
Why 6mm² input on PV?
Because it can only take 15A short circuit input. So you don't need anything bigger.
Use y connectors to combine the panels. Or change the design to 2s 2 p. Chances are with 60W you could go with 4s 1p. But check the maths there for VOC at min temps.
6mm² battery cable.
Because for 15A output you don't need anything bigger. That is all you can fit there.
The problem on a sailboat is, that you most likely have shading almost everywhere and panels in series are not performing that well...
But you should defilitly change the position of the MPPT charger. This should be locaed as close as possible to the battery. Not only because of the voltage drop across the battery cable that is higher as on the PV side, but also because of the temperature compensation.
Better is to put the panels in parallel using some Y-adapters and have this cable running 6 or 8 meters across your boat and have the chareger places directly at the batteries.
