wolfandy avatar image

MPPT and Pylontech - do I need a BMV?

Hi all

I am currently running a non-Victron integrated MPPT/inverter together with 2x 3.5kWh Pylontechs and 9 panels. I have a Raspberry Pi solution in place that connects both to the inverter and the Pylon BMS and controls the inverter modes according to the BMS SOC (rather than voltage reading).

As the built-in MPPT is of older generation, I am now contemplating adding a Victron MPPT 250/85 to the system and moving my panels (and using my current unit purely as inverter).

What I do not fully understand yet is if I need to establish some form of communication between the Pylon BMS and the Victron MPPT? I've read about VE.Smart Networking but do not understand what the benefit of adding a BMV (or SmartSense) would be.

Can anyone here please help me understand?

Thanks in advance

MPPT - Solar Charge ControllerPylontechVE.Smart Network
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1 Answer
JohnC avatar image
JohnC answered ·

Hi @wolfandy

There's a little about interfacing Pylon here:

This is sorta all Victron can 'support'.

What you'll need is a GX box, a number of varieties available. Or even indeed an rPi, which can handle the open-source Venus OS firmware.

So no, you don't need a BMV or any Smart kit.

The trouble is Victron have parallel types of systems, each with a purpose, and you need to select which from the confusion. Then add in the options you want.

The GX is the premium end, but give it some www, and the free VRM portal, and you'll likely want more of that..

Keep researching until you know enough to justify the spend on anything. You're doing that already of course, keep it up.

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Thanks for the feedback, @JohnC

But I still do not fully understand the benefit of having the MPPT and the Pylon communicate (via GX or any other system). What is the benefit? What information actually gets passed between them? How is it better than setting the charging voltages on the MPPT initially via Bluetooth app and then having it measure the battery voltage at its terminal (cable between MPPT and Pylon will be less than 1m)? How would knowing the SOC from the Pylon BMS change the MPPT behaviour compared to standard voltage measurement? I don't need to worry about the Pylon's temperature as I live in a place where it never freezes...

I understand that knowing the BMS SOC will allow an inverter to more accurately switch between battery and grid mode (rather than voltage which might not accurately represent the actual SOC due to sudden drops from higher loads being switched on). But I do not understand if a similar advantage exists for the MPPT.

The other challenge is that I will not be able to also connect a GX to the Pylon as the Pylon's CAN port is already used for the connection to my rPi controlling the inverter. The software currently running on the rPi is also capable of reading performance data from the Victron MPPT and post it to Emoncms. If I ever go fully Victron and also replace the inverter, then I understand that a GX will be required to run ESS.

If the BMS detects a cell problem you must limit or stop charging/discharging.
This is what the GX device do, it receives data's from the BMS and give this infos to all other devices.

What do you do to cut-off the power to your inverter?

Maybe you can use the "dry contact terminal" (page 7):
Not sure how this terminal works.

wolfandy avatar image wolfandy Matthias Lange - DE ♦ ·

Ok - thanks for the info.

At the moment I only have a manual breaker between my Pylons and the inverter.

The Victron mppt is essentially a client device, and will just do as it's told. And what it needs to do is up to the Pylon. The GX link is tested & approved.

Your 'other challenge' may not be as big as you think. GX is a suffix for Victron kit equipped with open-source VenusOS, and can be loaded to rPi, giving you an 'rPiGX'. This is at least semi-supported by Victron, they don't mind.

You're probably attached to your Emoncms, but VRM is quite spectacular, and under continual development by full time staffers. The Victron website has a demo setup, and you could try it out. You'll need to delve quite a bit to see all it can do, and there's not much it can't.

I think rPi questions on this Community are placed in the Modifications section, and you could look there too.

Food for the enquiring mind, hey?

It's not Emoncms that I am worried about (I'm actually not even running it).

My rPi runs a software called ICC that switches my inverter between battery and grid based on the SOC reading from the Pylon BMS (which my inverter otherwise can only do based on voltage).

So I would lose an important functionality in my system if I connect the Pylon to a GX. Which is why I am trying to understand the benefits of doing so in my setup :-)