How might I set up the Victron BMV702 relay to control a battery isolator device (a Battleborn lithium battery isolation manager)? I want to be able to disconnect charging amps from the alternator when the house Battleborn lithium bank reaches a certain voltage during a long drive. I have Victron solar charger and 600 roof watts to finish charging the 300 amp hour bank with more control than the alternator. This is in a Mercedes Sprinter mobile home. 
This should work...but...
In a good design you want to set the voltages of the charging sources to a safe level, like the maximum absorbtion voltage. The BMS is only to protect when an anomaly happens, like overvoltage in a cell or (when a charging source is malfunctioning or not set right) complete overvoltage (and undervoltage events, also shouldn't occur).
I strongly advice to get the charging voltage right, I don't know how high it is now and what it is allowed to be, sometime using an old style diode splitter (use both outputs to the battery) is enough to get a voltage drop and stay in the 'safe zone'.
