question

Take a look at the MPPT calculator:

https://www.victronenergy.com/mppt-calculator

I know that page but its not easy to understand.how is that Canadian solar 470w/44v cs3y/470mb 4 panels are all ready 130% oversized value for the 250v/100a mppt?44v x4 is 176v and multiplied by 10.74amp per panel so this is 44V×4(panels)=176v and multiplied by 10.74a=1.9kw but the mppt in theory is 250V×100A=25kw(this is what the mppt should handle) this is what I don't understand so on the page at the calculator it shows at temperature max 70° and lowest -20° and 10m cable length of 6mm thickness that for 4 panels in series it says PV max V@min temperature 234.6v and PV min V @max temperature 150v and that my mppt 250/100 it will be 130% oversized(wich in theory should be ok).why it can take only 4 panels?its an 250v and 100a charger so it should handle few more strings in parallel.this is very confusing.i want to connect panels 5 panels in series to have an very early charging start-up but 5 it shows in victron page that there is no mppt that can handle this.hmmmm....

I think you are mis-understanding the model numbering system for the MPPT.
"250/100" equates to a max input voltage of 250V (after temperature corrections) and a max output current of 100A. As you have a 12V system the nominal PV power (from the data sheet) is 1450W, (ie battery charge power of 14.5x100), so the "oversizing" is based on that value.
According to the MPPT calculator you could do 2 parallel strings of 4 in series (with that 470W panel), ie 8 panels? This would be 259% oversized... you would need to consider cooling of the MPPT in the summer as it would be working hard for much of the daylight hours?

My friend "gazza" wouldn't 259% be to much doesn't matter how much you are trying to cool it down?in my country in the summer we reach 40° most of the day's(of course the mppt won't stay out in direct sunlight i will build an shed with sandwich panel wals to try to keep the temperature as stable as possible)Will it be better smaller panel watt for example 400w so 4 in series and the 2 strings in parallel?thank you for taking the time and answering