question

Marty avatar image
Marty asked

What is the difference between VE.Can, CAN-bus ports and BMS-Can port?

RESEARCH

1. https://www.victronenergy.com/live/venus-os:start

2. https://community.victronenergy.com/questions/118934/bms-can-ports-running-the-vecan-nmea2000-protocol.html

3. https://community.victronenergy.com/questions/77903/250-kbitss-battery-on-multiplus-ii-gx.html?childToView=118964#answer-118964

4. https://community.victronenergy.com/questions/53457/can-i-connect-more-than-one-bms-to-the-venus-gx.html


From

[1].(15) - BMS-Can port is a port dedicated to be used for connecting managed batteries

[1].Second CAN-bus port (also features BMS-Can (18)) 1.(18) The secondary CAN port,

available on some GX devices as per table above, can be configured

to be used as a BMS-Can port, as well as other profiles

Thus it is suggested that the "BMS-Can" is a "Feature" added to the construct of CAN-bus port. However 1.(14) states "The hardware does not meet the requirements for a VE.Can port; and therefore is BMS-Can only. "

While[4] states "The BMS-Can protocol doesn't use addressing". (I believe protocol should be port).

Furthermore it is inferred the BMS-Can port and CAN-bus port are really running the VE.Can / NMEA2000 Protocol but ignoring the addressing priority built into the protocol (maybe through some hardware omission in hardware or protocol stack).

Question 1. Thus, what is the difference between VE.CAN port, CAN-bus port and BMS-Can port?


Question 2. Some GX devices (Venus GX and Octo GX) have secondary ( non-isolated) CAN-port with active BMS-bus feature. [1.(18)]. Does then mean a second battery can be monitored and managed by the Venus or Octo with the active second port? If so, can the batteries have separate Shuts or system voltages?

VE.CanNMEA 2000 - N2K
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3 Answers
wkirby avatar image
wkirby answered ·

The VE.Can port is galvanically isolated and the BMS Can or Second Can port is not galvanically isolated.

Connecting two batteries to one GX device, having two different batteries on one system is not intended. Only one battery could be assigned as the system battery and the other one would just show up in devices for casual observation.
You would not connect two different batteries to the inverter / charger system so that is why only one battery bank makes up a system.
Either combine the two battery banks as one, if possible, or have a second GX device to create a second separate system.

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Marty avatar image
Marty answered ·

Hi wkirby and Community,

Thanks for response. Could you help me clarify some term:

1. Are we saying that BMS-Can port and CAN-bus ports are the same?

2. Are we saying the BMS-Can port / Can-bus port are really the VE.bus port?

If NO to either

3. Where are the BMS-Can ports on the MultiPlus-II GX ? ( I only see VE.bus port but yet from the table at [1].(14) it indicates that the MultiPlus-II GX has BMS-Can port and the Can-bus port is NON-Isolated where as the VE.bus port are Isolated )

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wkirby avatar image wkirby ♦♦ commented ·

1. VE.Can and BMS-Can are both Canbus ports.
VE.Can is always presented on a pair of 8P8C connectors to daisy chain the bus or to accommodate a terminator. Must communicate at 250kb/s, can do 500kb/s
BMS-Can or a second Canbus port which is not designated as VE.Can could be presented with either one, or a pair of, 8P8C connectors or pluggable terminal block, could be isolated or powered. Could be 250kb/s or 500kb/s or configured for either.

2. VE.Bus is not Canbus at all. It is a Victron propriety protocol based on RS485.
You'll only find this on Inverters, MultiPlus', Quattros, the GX monitoring devices and MK3 configuration interface.
It's used for mission critical communications keep groups of inverters at the right phase angle. Also for configuration and monitoring of such devices.

3. The MultPlus II's BMS-Can ports are presented here:
1643918327497.png

These do not meet the requirements for VE.Can. It can only communicate at 500kb/s so that is why it is BMS-Can and not VE.Can.
The VE.Bus ports are presented here:
1643918743040.png


I've probably missed something out, but I hope what I have there helps to clear things up for you.

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1643918327497.png (42.4 KiB)
1643918743040.png (20.3 KiB)
nebulight avatar image
nebulight answered ·

Revisiting this thread. I think I may already know the answer but with the addition of the RV-C protocol I’m interested in using seelevel tank senders on the ve.can port but also will be using a rec BMS and Wakespeed regulator. Both can do 500kbs but not sure if they require the isolated port. I may just have to wait for Victron to release their second gen cerbo next year if it won’t work.


Thanks!

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