CANbus ports for motordrive -- does BMS-CAN port work?

Q&A and troubleshooting
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1

What it says – for connecting a Sevcon Gen4 controller using the new motordrive option, can this use the (11b) BMS-CAN port or does it have to use the (29b) VE-CAN port?

Right now I have a REC-BMS connected to the VE.CAN port running at 500kbps, and AFAIK the Sevcon is set to 250kbps, so unless it’s reprogrammed (which I don’t have the hardware/software to do) they can’t share a port.

Am I right to think that if the Sevcon was reprogrammed to 500kbps it could share the (29b) VE.CAN port? (daisychained with BMS)

2

Any comments from those in the know – for example @UpCycleElectric @mpvader ?

3

needs to be a real VE.Can port

4

Thanks @mpvader , I suspected that was the case but I thought I’d check.

Am I right to assume that daisychaining on the VE.can port (Cerbo only has one) will be fine so long as baud rate is the same as the BMS?

If not I’ll have to replace the Cerbo with a Mk II (ouch!) and run another CANbus cable through the bulkhead to it, which is awkward too… :frowning:

5

Hi @iand , yes absolutely, you are correct.
However, there are no can profiles that will have both the CAN-bus bms service and the CANopen motordrive service running at the same time.

Would it be possible to plug the REC-BMS on the BMS-CAN port and the Sevcon controller on the VE.Can port?
The REC-BMS documentation states that it should be connect to the BMS-CAN port on a Cerbo.

Just for reference:
The baud rate of the Sevcon controller can be changed at SDO 0x5900.02.
Here are the possible values for that SDO: 0=1Mb/s, 1=500kb/s, 2=250kb/s, 3=125kb/s, 4=100kb/s, 5=50kb/s, 6=20kb/s, 7=10kb/s.

Your first step could be to confirm which baud rate your controller is using by connecting the controller to the Cerbo VE.Can port (disconnecting your BMS temporarily) and switching between the 250kb/s and 500kb/s CANopen profiles, run the scan and check under which profile it can find your controller.

6

Thanks for the help Nils :slight_smile:

I won’t actually be doing this myself, the boat is going back to the boatbuilder early next year to have some other work done, and they’ll be connecting up and configuring the motor drive while it’s in their workshop.

If the BMS and Sevcon could be daisychained then that would be simplest, the Cerbo is inside the cabin with a CANbus cable running through the bulkhead to the BMS under the stern, this is where the Sevcon also is so this is just adding one easy-to-run cable from BMS to Sevcon.

If the BMS and Sevcon have to be on two different ports and the REC-BMS is happy on the BMS-CAN port then this can be swapped over, but then another CANbus cable has to be run through the bulkhead and access is not easy (cabling run is behind the isolation transformer).

If they need to go on separate VE.CAN ports (not BMS.CAN) then the Cerbo V1 will also have to be replaced by a Cerbo V2… :frowning:

It seems strange that both services (CAN-bus and CANopen) can’t share one port since the hardware signals are compatible (and CANbus is designed for daisychaining), but I guess that’s not how the Victron software is configured, it’s one or the other?

7

Yes, it’s one or the other.

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While CAN-bus BMS and CANopen E-drive can be connected on the same physical hardware port/CAN-bus, at the software layer both protocols could have conflicting CAN IDs that could interfere with each other.
I haven’t checked, but anyway this is unlikely to change.

I think the options are:

  • Use the BMS-Can port for the REC-BMS if possible.
  • Switch your GX device to one with two VE.Can port.

Either way unfortunately it would involve running another cable