This BMS is ONLY for Victron Smart Lithium Batteries. It doesnt work with any other kind of batteries, not even with other brands of lithium battery. It has a data cable that connects to circuitry inside the battery.
Its quite normal to have a starting battery with a different chemistry. The BMS can control devices such as the Cyrix-Li-Ct that can combine the two different banks under certain circumstances but doesnt directly interact in any way with the lead acid battery itself.
My blog section on Lithium Batteries has more details