project fitting 40kw pv solar panels to barn and installing 3phase invertor staying totaly off grid battery backup systems will be fitted at a later date i welcome all thoughts and comments 

using a trina solare 425 panel (102) of them in total with a hybrid invertor (not chosen yet) input welcome on invertors  will need to be able to ev charge , battery charge, 

Welcome, fellow welsh person !
EV charging is a challenge, as you’ll be at 7kW max, with that needing to be sustained. 
Have you ruled out a diesel genny? 

i already have a genny back up system if needed but the cost would be high to run

i am on grid with a 3 phase with a 100 kva supply and as you can imagine cost are high hence the reason for adding a helping system of pv 

40kw 3 phase is a substantial input into reducing cost 

from 40 kw i would estimate through the winter time i may get 30 -50 % input from the panels can you explain what you mean by 7kw max with regards to ev 

alough i don t expect to be totaly off grid all the time and having the ability of the grid input my energy bills should be dramaticaly reduced on a monthly basis