Victron EV charger with modifications

I want to “modify” my charger to have two relays, first for only one phase and the other for the remaining 2 phases. I got some questions about this modification.

The on board relay control lines I assume shall go to the first relay(L1 and N). Is that correct?

What more shall I do on the MODBUS side?

Will 1P/3P be automatic detected in EVCC for the Victron charger?

Thans in advance :slight_smile: