Additional PV panels - Use the other MPPT input or series two arrays? Most efficient wiring?

[Flatpicker]

I have a Sungold 8 kW split phase inverter with 10 kW (soon to be 20 kW) of wallmount batteries. Two EcoWorthy dual axis mounts with a total of four 560 Watt bifacial cells wired in series. VOC for each panel is 50 volts. Total string voltage when connected to the inverter varies between 160 to 180 volts. This string is wired into one of two MPPT inputs. Maximum voltage in on the inverter is 500. I’m not sure, but I think the inverter won’t even “break-over” and function unless it sees at least 125 volts. I plan to add another four identical panels in the future.
My question is this: If I add another four panels, is one way more efficient than another? Do I place them in series with the existing arrays for a voltage of 320 to 360 volts, or do I place the four panels on the other MPPT input? Does a higher voltage boost efficiency of the inverter? Does it even matter? Thanks!

 

[DIYrich]

If the location of the panels are identical, and no shading issues, then it might be easier to add in series - uses existing wire to the inverter.

If orientation is not the same (or shading difference), then the 2nd mppt is good to optimize each set of panels.

 

[n2aws]

If the location of the panels are identical, and no shading issues, then it might be easier to add in series - uses existing wire to the inverter.

If orientation is not the same (or shading difference), then the 2nd mppt is good to optimize each set of panels.

Adding on to this.. (again assuming panels,voltages, and orientation are identical and no shading). wiring them in series increases the voltage. higher voltage means less loss in the wires assuming you are within the safe operating limits. If any of the above aren't true, then it's probably better to run them into their own MPPT controller so that each one can harvest the maximum out of the individual arrays.

 

[Hedges]

Depending on specs and shading, second identical string but of different orientation could be connected in parallel to same MPPT. Leaving other MPPT for additional PV in the future.

If same orientation, see if documentation quotes efficiency voltage, or conduct tests to see if series or parallel delivers more power.
The difference in efficiency shouldn't matter much in terms of power delivered, but slight difference in efficiency is large difference in power dissipation, affecting lifespan.

If presently near minimum MPPT voltage and shadows at times knock it below, then series could be better.

Multiple MPPT likely more efficient due to lower I^R losses. Also increasing longevity of MPPT circuit.