We've got 4x100 panels, 35A chg ctlr, and a 2k psw inverter. 4 x 12V bats on coach w/1 reserved for gen. Mobile aux bat box & monitor with 4x6V bats added in parallel w/ winch quick power disconnects when boondocking allows for 2 weeks with nights at 25 degrees outside w/furnace running enough to keep the thermostat at 68, without getting up to start the gen (but able to if needed). Will upgrade to 8 panels eventually to hasten recovery on overcast days, but pretty sufficient so far.
What kind of amps are you seeing out of 400 watts being sent to the battery for charging? is your controller a MPPT or PWC