My installation is formed by 2 strings of 5x485W panels + MPPT 250/60 + Multiplus II GX 5KV + 2x5Kw·h Dyness batteries. I can only achieve a max solar power of 3.3 KW limited by the 60A of MPPT. MPPT is configured as “external control”.
I think the best solution would be to add a new MPPT 250/60 and connect each string to an MPPT. I’ve checked the wiring and seems simple, also the configuration of the VE.Smart Network so both MPPT work as a one.
My question is: The MPPT is wired to the Multiplus through VE:direct port, and there are no more VE.direct ports available in my Multiplus II GX. Do I need to wire the new MPPT to the Multiplus using and VE.direct to USB adaptor or, as it will work together with the first one, the wire is not needed?
Not necessary, VE.Smart is intended for small installations, but since you want to connect the MPPT over VE.direct onto your existing GX a VE.smart network has not really a benefit.
A USB-to-VE-direct adapter can be used, either the official Victron one with one VE.direct port, or as an alternative the four port hub
In general, an MPPT does not need any communication with the GX or with other MPPTs, it can work fine by just regulating based on the battery voltage. Communication mainly serves to read out metrics and change settings remotely