You've done a good job of clarifying your requirements, I can't recall a thread that doesn't get off track.
The MPPT controller input vultage MUST be greater than the combined panels Voc (open circuit) voltage plus panel voltage temperature variations to protect the electonics. The typical 12V panel Voc is about 21V, so make sure the MPPT controller inut is about 42V + 10V for low tempeatures. This is not the charging voltage.
Vmp (maximum power) is the panel charging voltage about 18V for a 12V panel. So the panel output is 2*Vmp at Isc (short circuit which is usuall be best spec for amps).
Now subtract the panel to controller wiring voltage loss. Subract about 5% loss for the MPPT controller, convert the resulting power to amps at 14.4V for the battery. With the controller near the battery you can ignore that wiring loss.
