question

sylk avatar image
sylk asked

Ve.can termination, but where?

Hello all,

I made below a scribbled plan to my system.

The 2 right mppt's on ve.direct and the pylontech batteries with their bms connected om ve.can were working for some time without problems. Pylontech bms connected to ve.can was installed without any terminators, either on gx or the battery and it worked fine.

However, needs arrised for a 3'rd mppt. I can t connect it on ve.direct, since i have only 2 ports. Simple connection on the free ve.can port did nothing, so i figured out i need terminators. But where should i put them? On mppt only, or on mppt and on the pylontech battery? Wich one, first, or last?

Thank you!

img-20230520-084605.jpg

MPPT ControllersPylontechVenus GX - VGXVE.Can
img-20230520-084605.jpg (3.5 MiB)
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5 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi all,

The Venus GX has two independent CANbus interfaces. One with the RJ45 sockets, which can be set as either VE.Can or BMS-Can.

The other are terminal connections and cannot be set to VE.Can, only to BMS-Can. So it is that one that you should connect your Pylontech batteries too.


Both CAN interfaces specify using a terminator at each end of the bus. In the case of the Venus GX, as the BMS-Can terminals are not RJ45 is not so easy.

One terminator should be used on the Pylontech end, that is straight forward.

It IS possible to use a specific resistor (that is what is inside the supplied RJ45 terminator) to the Venus end. However given that the battery is the only thing on that bus, and presumably the cable is only a few meters long, and you can route it so that it is far away from any electrical interference (don't run it along side the power power cables), you should be able to work without it.

The terminator is there to absorb an electrical echo that can cause interference back on the line. The noisier the line, the more signals, and the longer the cable, the worse the effect and the more important the terminator is.

If you DO have issues with battery communications, then come back and we can look into what next.

This was all simplified with the Cerbo GX where both CANbus interfaces use the RJ45 sockets.

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scoraigwind avatar image scoraigwind commented ·

Hi Guy,

I am planning to connect a smartsolar 150/100 ve.can MPPT controller to a Venus GX. The first canbus RJ45 socket in the Venus is already used by the BYD battery BMS. So I plan to use the CAN 2 port in the venus for the MPPT. I can see in the services menu on the remote console of the venus that it is possible to set up 250kbit speed on this 3 pin plug can 2 port. So that is what I planned to do for the MPPT.

But reading the above Accepted Answer I wonder if this will be possible. But why should it not be possible to use CAN 2 in the Venus as a ve.can connection at 250 speed for the MPPT controller? Thanks for any explanation why we need to use CAN 2 for BMS and never for VE.can.

I plan to wire a 120R resistor between the CAN-H and the CAN-L pins as a terminator.


cheers

Hugh

can-bs-profile-menu.jpg

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can-bs-profile-menu.jpg (90.9 KiB)
Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ scoraigwind commented ·

Hi @scoraigwind,

Edited to remove incorrect info, this information below is now correct.

Both CANbus interfaces of the Venus GX are able to support VE.Can

https://www.victronenergy.com/media/pg/Venus_GX/en/connecting-victron-products.html#UUID-86f0c9ce-19b8-9f83-6745-de4b950fc268

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scoraigwind avatar image scoraigwind Guy Stewart (Victron Community Manager) ♦♦ commented ·
Hi Guy,

Thanks, it is useful to know this. The Remote Console services menu suggests that it can be configured for 250kbits/sec as in the screen shot I shared, but I guess this is not true after all. Perhaps the menu could be updated to reflect this limitation.

cheers

Hugh

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ scoraigwind commented ·

Hi @scoraigwind

I just edited my post to confirm that both CANbus interfaces on the Venus GX are supporting VE.Can, so the software and the manual are correct :)

https://www.victronenergy.com/media/pg/Venus_GX/en/connecting-victron-products.html#UUID-86f0c9ce-19b8-9f83-6745-de4b950fc268

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ejrossouw avatar image
ejrossouw answered ·

The Pylontech string will require a one terminator on the Venus device. I propose you purchase a VE.direct to usb dongle to connect the 3rd MPPT to one of the usb ports. The VE.can MPPT cannot be on the same string as the batteries.

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dansonamission avatar image
dansonamission answered ·

The Pylontech batteries will be running at 500kbps where as ve.can devices, such as the Victron mppt run at 250kpbs. Your best option is the ve.direct to usb adapter as mentioned above.


https://www.victronenergy.com/accessories/ve-direct-to-usb-interface

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hjohnson avatar image hjohnson commented ·
Cerbo GX's have two CAN ports, one of which (BMS-CAN) can operate at 500kbps. That should be able to communicate with the pylontech batteries, and then the MPPT can be on the VE.CAN interface. a USB->VE.Direct dongle would do no good, as that MPPT speaks CAN, not VE.Direct.
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nickdb avatar image nickdb ♦♦ hjohnson commented ·
He has a venus not cerbo and CAN mppts also are equipped with vedirect ports.
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sylk avatar image
sylk answered ·

Thanks a lot guys! You saved me from upgrading to a cerbo, i thought ve.direct to usb is only for connecting to pc.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·

Reading the manual also helps. :)

https://www.victronenergy.com/media/pg/Venus_GX/en/installation.html#UUID-d0c1e103-df9e-4691-b369-33d047b01491

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sylk avatar image sylk Matthias Lange - DE ♦ commented ·
Reading the manual told me that Venus gx has a non isolated bms-can port. Why can t that be used for pylontech, instead of occupying the ve.can port?
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4711austria avatar image
4711austria answered ·

if the Can sockets are not used on the Cerbo, should the terminator be placed on the Cerbo?

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pwfarnell avatar image pwfarnell commented ·
@4711Austria No, terminators are not required if the Can sockets are unused.
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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ commented ·

There is no harm in putting them in. I would tend to because it will stop dust and debris from entering the ports, and you're far less likely to lose them. They'd be serving no other function though.

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maa avatar image maa commented ·

A stripped RJ45 plug in all unused ports on your Cerbo is also nice. this is my credo

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