question

@Tony, the BMV-712 is (once properly programmed, and so long as it's properly connected) an extremely precise measuring instrument of loads down to one or two tenths of an amp, so you should absolutely get it.

The most important thing to remember in hooking up the BMV is that the negatives of all chargers and loads, including any NEG buses or chassis grounds and certainly including your MPPT and Quattro negatives, must be connected to the "loads/chargers" side of the BMV's shunt; the single negative battery cable that should be coming off your bank goes to the "battery" side of the shunt. So long as you don't bypass the shunt with ANY system negatives, it's the most precise and dependable monitor on the market.

The Venus GX and the BMV play very nicely together; I cannot, however, speak to the BYD system and how it interacts with any other components, as the BYD brand isn't one we stock or service, so I'm unfamiliar with its specs. Obviously it won't be directly communicating with the other components since it's not a Victron, but that should be more or less irrelevant because the BMV is measuring the battery bank and reporting that data to the Venus, so I don't see any reason why you shouldn't be perfectly happy with the level of component integration you experience. That being said, I definitely defer to anyone with experience with BYD systems.

Hi Tony

I have a BlueNova LiFePO4 battery which has the same limitation as the BYD battery - i.e. poor State of Charge accuracy when used with low-level loads. Adding a BMV-712 to my setup (MultiPlus-II 3k) made a huge difference and I would strongly recommend doing this. See the graph below that compares the SOC reported by the BMV-712 and Battery BMS. Proper control of your system (e.g. via ESS) is virtually impossible without a reasonably accurate measure of the actual SOC.

The VenusGX/CCGX can be configured to take the SOC reading from either the BMV or the Battery.

The additional data (temperature, cell imbalance, under-voltage/over-voltage warnings etc.) from the BMS is still available even if the SOC value is obtained from the BMV712.

Regards, Nigel