question

Battery bank is 12volt.

Hi @shars.p

Use this calculator: https://mppt.victronenergy.com/

That is a very high panel Voc, and unless you have a 250/ rated mppt you'll need to wire them in parallel anyway.

If just a 150/ unit, parallel should work fine anyway into any batt V. The MC4's run to a common bus, so it's just a convenience thing.

I have just re-read the PWM vs MPPT whitepaper at Victron.com and if I read it correctly, PV panels should be wired in series to max voltage going in up to the limits of the regulator. The regulator then performs its P=VxA magic. This was my understanding originally and my plan was always to wire in series. I suppose what I am trying to understand is how the MC4 PV inputs behave ie are they going to series my PV inputs inside the unit if I just connect each panel to a pair of MC4's or are they just a parallel input? If parallel then I assume that the regulator will operate the most efficiently if I series the panels and then connect just as i would if I had a Tr version.

By the way my controller is a 250/80 MC4.

JohnC is correct. With that combination oif panels and controller, you can pretty much wire them as you you like.
However, you are right, the controller will operate a bit more efficiently with the panels in parallel (Voc 75V), also this w configuration will help with any shading issues.

The MC4 connectors are all in parallel, so wire each panel to a pair of MC4 connectors to have the panels in parallel

My understanding is that it's a good idea to have over-current protection in place when paralleling more than two strings of panels. If a 3 input MPPT charger is just connecting the panels to a common bus, then hopefully the manual would instruct you on having appropriate external fusing?