To use both the DC to DC or the BMS CL 12/200 you need to have a lead acid battery on the output of the 12V alternator. The DC to DC or BMS installs between the lead acid and the lithium. Look at the manuals for both these devices and they show a lead acid battery.
There are 2 reasons for this. The alternator needs a battery to act as a buffer to smooth out voltage control. Many people have tried without and report voltage and current cycling as there is nothing to moderate the system if the control systems in the alternator and charge control interact. Secondly, there is an issue called load dump, if the lithium battery is charging at high rate and the BMS disconnects the alternator can not respond quickly enough and the voltage can spike to 70V, blowing the alternator diodes plus other electrical equipment. The lead acid battery would need to be small, say 50Ah.
One way to deal with some of this is an external regulator such as the Wakespeed WS500 or Arco Zeus.
Another issue with the BMS is what voltage the alternator outputs, see BMS and alternator voltage