You are still not very clear. I am aware of the Victron company and the sort of products it produces. What I was hoping to find out is exactly what Victron product you are using. I also know what mppt is - I have solar panels on my boat (this laptop is being powered by them right now) but I don't have an mppt myself.
It sounds as if you have a Victron mppt device and a separate BMV device and both of them can send out serial data.
What is not clear is how they send data - for example are they both continuously sending data so that if you listen to one device you miss data from the other? OR, do you have to do something (send a request, for example) to cause one or both devices to send out a message.
You said earlier "The Victron software interface could not make heads or tales, I could see the software query the Arduino and it will do that for a couple of secs and then say no device found on both the states" but I don't understand the underlying context so I can make sense of that or suggest a solution.
...R