From the following research
1. https://www.victronenergy.com/upload/documents/Technical-Information-Data-communication-with-Victron-Energy-products_EN.pdf
2. https://www.victronenergy.com/live/battery_compatibility:can-bus_bms-cable
3. https://www.victronenergy.com/upload/documents/MultiPlus-II_GX/MultiPlus-II_GX-en.pdf
4. https://community.victronenergy.com/questions/53457/can-i-connect-more-than-one-bms-to-the-venus-gx.html
5. https://www.offgridsoftwaresolutions.com/ws500-user-forum/topic/connecting-my-rec-bms-to-a-victron-cerbo/
Since there is no BMS-Can protocol listed in [1] and the cable for VE.Can are used on the BMS-Can ports (CAN_L, CAN_H, V-, V+) on pins (8,7,3,6) where Vdiff (V+ - V-) is 9 to 32 V [2] and there are restriction on what can and can't be used on BMS-Can Port [3] because there are not using the address scheme in the BMS-Can port [4]. I would infer the BMS-Can port are using the VE.Can / NMEA2000 Protocol but ignoring the addressing priority built into the protocol.
I am not sure if that makes sense, but the concept of the "BMS-Can Port" is just to allow a single BMS battery to be control from the port even though it is a Daisy protocol that could be plugged into a VE.Can port like the Rec-BMS was " plug into the VE-CAN port on the CERBO rather than the BMS-CAN port and set CAN-1 settings to VE.CAN & CAN-bus BMS (250 kbit/s)" [5]
