Ve Direct vs VE Can

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logic28 asked Jul 25, '23

Ve Direct vs VE Can

I've read most posts with regard to this subject but it is still unclear to me why, given the choice, I should choose VE-Direct instead of VECan or vice versa when connecting my two identical MPPTs to the Cerbo unit.

By that I mean what is the difference between the two protocols, if any, in terms of speed, reliability and efficiency.

Is VE-Can the latest technology introduced or is it the other way around?

I would have thought that, as the name implies, VE-Direct, being hard-wired, would be more practical compared to other serial interfaces.

Any comments, please?

VE.Can

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Herve RV Nizard answered · Jul 28, 2023 at 06:38 PM

As recently discovered , one of the differences between VeDirect and VeCan for MPPT's is that when using VeCan , you will only see 2 days history of your MPPT on your GX device or remote console ( GX device / device List / MPPTxxx/ Daily history) . When the VeDirect will give you 30 days history.

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logic28 commented · Jul 29, 2023 at 09:59 PM

That is exactly one kind of unexpected finding I was looking for, thank you for sharing your discovery.

That makes me wonder why transitioning from Direct to Can Bus and what can the latter cater for that the Direct could not

I was also wondering if the lower bound rate of 19200, even slower than the vintage MIDI musical instruments protocol at 31,250 vs 250k of the Can bus (RS485 based) would affect the performance significantly

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Alexandra ♦ logic28 commented · Jul 30, 2023 at 05:39 AM

The thirty days is still on the mppt. So if you need to look at it the information is still there on the mppt itself.

Can allows alot more devices to be connected at a lower cost. There are also a few other advantages, but you mainly see them in larger installs.

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Modifications Space

Node Red Space

Answer 1 · 2023-07-25T20:28:18Z

nickdb answered · Jul 25, 2023 at 08:28 PM

It doesn't really matter, both as functional and reliable.

With multiple devices, it is easier, possibly cheaper to wire a chain of CAN devices, rather than individually linking devices back to the GX via VE.direct.

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logic28 commented · Jul 25, 2023 at 08:44 PM

Good, however, it would still be interesting to know the internal arrangements of the two, I am puzzled by the fact that they still offer two different interfaces, one point-to-point and one in cascade mode like RS485 or indeed DMX protocols which do require more ID exchange data. Thanks for your answer.

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nickdb ♦♦ logic28 commented · Jul 25, 2023 at 08:50 PM

There are many devices with only VE.direct. Even the CAN devices also support VE.direct. It is a very open architecture that looks after a broad range of devices of varying ages for long-term compatibility.

Don't overthink it.

There really is no difference of one vs the other, apart from what makes the best sense to build your unique configuration.

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Answer 2 · 2023-07-25T20:39:38Z

Kevin Windrem answered · Jul 25, 2023 at 08:39 PM

The choice is yours. I doubt you'd see any performance differences.

VE.Direct is a point-to-point unbalanced serial connection where as VE.Can (aka CANbus) is a balanced (RS-485) multi-drop connection. I think VE.Direct came first in the Victron world.

VE-Direct requires a connection on Cerbo, etc. for every device and at most there are 3 ports. You can extend this by using a VE.Direct to USB adapter cable.

VE.Can is physically different from CANbus. VE.Can uses ethernet cabling, looping through each device. CANbus uses a unique connector with "taps" to go to each device. You can interconnect VE.Can to CANbus with the appropriate adapter. The entire network is terminated at both ends with a 120 ohm resistor. VE.Can/CANbus is limited to about 100 devices. VE.Can/CANbus operates at one of several baud rates and in the Victron world, this rate must be the same for all devices on the same port. Additional VE.Can ports can be added to Cerbo via a USB to CANbus adapter.

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logic28 commented · Jul 25, 2023 at 09:11 PM

The entire network is terminated at both ends with a 120 ohm resistor.

Yes, I'm familiar with the RS285 protocol, I have used it in the form of DMX for stage lighting with the same terminators to avoid bouncing signals (even though it often works without) much more complicated than the former RS232.

Still, Victron specs seem to lean towards using the three data connections, one for the inverter, the second for Linx devices and lastly VE-Direct for MPPT.

I suppose I'll have to make a decision also based on keeping the cabling tidily arranged.

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ve-bus-ve-can-direct.jpg (377.9 KiB)

Answer 3 · 2023-07-27T08:11:42Z

Michelle Konzack answered · Jul 27, 2023 at 08:11 AM

VE.Can is used, if you have the MPPTs with the VE.Can option, which allow you to balance certain settings across the MPPTs, like the Voltage settings and maximum charging current.

For this setup you do not even need a GX device because it works entirely Stand-Alone!

I have now a SmartSolar MPPT 150/70-Tr VE.Can together with my two new SmartSolar MPPT 250/100-Tr VE.CAN. No Color Control GX or Cerbo GX needed.

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Answer 4 · 2023-07-27T10:01:22Z

petajoule answered · Jul 27, 2023 at 10:01 AM

You will not see any difference in performance (speed wise), but VE.Can is somewhat more resistant to electronic interference (inherent feature of CAN, as is of RS485).

Because CAN has a daisy-chain-like bus topology, it's really well suited for larger installations where you would have to use way too many VE.direct ports (remember: OctoGX is not around anymore). Also it allows for somewhat longer connections/distances.

Last but not least it allows you to snoop on the bus. ;-)

In the picture above you are (ab)using VE.Can for a P2P/direct communication which, given the fact that the Cerbo has 3 native VE.direct connections, is misplaced love - sort of.

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