we know the problem when connecting VE.direct without isolation e.g. on a Venus Raspi system (when e.g. JK interrupts B-/P-, power from SmartSolar may (try to) flow over VE.direct ground)
Now I’m asking myself if it is safe to connect BMS CAN of a JK BMS PB series to MultiPlus II GX without isolation?! (CAN_hi/lo + Gnd)
In the manual of the Multi GX nothing is mentioned regaring isolation of the BMS CAN interface. In the Cerbo manual “1 x VE.Can (not isolated) and 1 x BMS-Can” is written, what makes me assuming that the BMS CAN is isolated.
Is it isolated in the Multi GX also?
thank you very much & greetings!
Phil
guystewart
(Guy Stewart (Victron Community Manager))
2
I checked the linked page but can’t find any info regarding isolation of the BMS-Can port. The only thing mentioned that “Late 2021 / early 2022, … MultiPlus-II GX … update … changes the CAN-communications port from a limited 500kbps BMS-Can only type to a full featured VE.Can port (non-isolated).”
But today there are two BMS-Can sockets and no VE.Can (according to the manual).
CCGX: yes, 2 isolated VE.CAN ports; oh no, later on the table tells there is no 2nd CAN port (What is this? Is there just 1 VE.CAN port, or are there 2?)
Venus GX: yes, 2 isolated VE.CAN ports; oh no, later on the table tells the 2nd CAN port is not isolated (Why not tell that at the “VE.CAN” row?)
MP built-in: depends, 2 isolated VE.CAN ports. (How to read that in combination with “Second CAN bus port: no”?; Note 24: “The update … changes the CAN-communications port …(non-isolated)”: One port is isolated and one port is not-isolated? But which one is the isolated port? The left one or the right one?
Such documentation, is not clear to me. Only documentation regarding the MK2 product its CAN ports isolation is clear to me.
It is essential to know which GX BMS/CAN port(s) is/are the isolated port(s), otherwise the BMS might damage in case DC-minus is disconnected.
guystewart
(Guy Stewart (Victron Community Manager))
8
The first table row says there are two VE.Can Sockets.
I have just updated the second table use the phrase ‘interface’ rather than ‘ports’ to hopefully make the distinction more clear.
What this means is that there is only a single VE.Can interface on the CCGX, but there are two ports because it’s a daisy chain topology.
Other products that have two CAN bus interfaces have 4 ports (except where they do not, like the Venus GX that uses terminal connectors instead of RJ45 ports for the second CAN bus interface).
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guystewart
(Guy Stewart (Victron Community Manager))
9
On the Venus GX;
The VE.Can RJ45 ports are isolated.
The 2nd CAN bus terminal connectors are not isolated.
I have added this terminal connector distinction to the table.
guystewart
(Guy Stewart (Victron Community Manager))
10
MP GX built-in:
There is only a single VE.Can interface, but it has two RJ45 ports in parallel to allow for the daisy-chaining of multiple VE.Can devices.
This product is specifically complicated because the functionality and isolation of the port has changed over time and as we have been able to improve the hardware.
I have updated the foot notes just now. Please read them again and let me know if it’s still not clear and I will make it even clearer. This one is unavoidably confusing.
@guystewart For MP/EasySolar GX built-in I read this as these GX devices nowadays have 1 non-isolated interface.
I would change the table. Split the row “VE.CAN” into 2 rows:
“VE.CAN interfaces [*] (isolated)”, in the device cell just the number, f.e. “1”
“VE.CAN interfaces [*] (non-isolated)”, in the device cell just the number, f.e. “0”
In case the title is too long, I would remove the word “interfaces” and let the footnote explain that
Where [*] becomes a footnote number, that footnote states something like: Number of interfaces. CAN is a bus system that allows daisy-chaining. Each interface consists of 2 connections. Sometimes the connection comes in the form of RJ45-port other times as terminal block (screw driver needed).
And for the “built-in” column, the number is “0 or 1” with the footnotes.
Are there GX devices with a CAN/BMS interface that consists of only 1 port instead of 2 ports (no matter what form)?
PS The page layout is too fixed: on a 1366px wide screen, only 1078px are used to display the table. A wasted blank margin of 144px of screen “real estate” on both the left and right side margins. Result: the built-in column is only partially shown and unreadable:
