I have had a SmartSolar 100/30 installed for around a month, and am going to install a 712 that just arrived.
While not critical, it'd be nice to be able to get the voltage from both of the batteries in my aux bank (2x LiFePo4 12v @ 180AH in parallel) just in case they get out of alignment (though the regulators on them should handle that) as well as temperature (so my smartsolar doesn't try to charge my batteries when they're too cold later in the year - more important!).
It seems like if I'm going to buy a bmv temperature cable for $21 that'll take the place of my second voltage sensing cable, I might as well just get a https://www.victronenergy.com/accessories/smart-battery-sense for my solar charger for $31 (well $39 for the newer version) and pull in temp with that and be able to get the voltage of both of my batteries.
Possible downsides:
1 - The voltage sensing on the bmv is supposed to be more accurate than that from the smart dongle, could that create conflicts?
2 - Having three things that need to communicate over bluetooth instead of two. Is the complexity worth it?