Anders avatar image
Anders asked

VRM Logic to control usage of excess PV energy

I believe the best way to utilize potential excess energy in a PV installation is to use all available data and set up rules for when (and how much) excess energy is available.

Last years story about AC-THOR involves a separate HW (non Victron) and use the CCGX as data source. In a couple of other threads on this community the solution is also to use additional HW, or the more simple solution only using one data source, i.e SOC = 100% flip a switch.

I do not understand why we need additional HW, and the "one data source, flip a switch" is way to inefficient i.e not being able to harvest energy when the MPPT throttle down in the absorption phase.

I have experimented with utilising the VRM alarm rules, and building the logic into my Gmail email filtering functionality. This is possible to accomplish by controlling the load basically by sending emails to my "Smart Cabin" using the simple and inexpensive functionality that comes with services like IFFT.

So.... for installations that have all the nice and advanced HW from Victron, MPPT, BMV, Multiplus, GX's , and are online to VRM with local inexpensive SmartCabin functionallity like Telldus. ..........

Why... can't we just get the logic built into the VRM portal very much like the alarm rules?

MPPT in Bulk mode - everything goes to the battery - no excess energy available

MPPT in absorption - apply load phase 1 (jut send me an email if you do not want to link directly to IFFT

MPPT still in absorption and PC power is increasing and battery voltage not dropping? apply load 2,

etc etc etc

Dear Victron experts - this ment as inspiration to make even greater functionality on the VRM portal

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3 Answers
Mark avatar image
Mark answered ·

While there are may ways to make something 'work' - I'm not so convinced that sending data to VRM, processing the data and then sending a logic decision back to the same location is a reliable or optimal solution to control high powered loads.

For high power dump load control you really do need to have some form of additional hardware, with the simplest form being a single relay/contractor (rated to the dump load), next is some form of 'staged' system with multiple relays (and small individual dump loads), but ideally a method to continuously modulate the exact power provided to the dump load is required.

It is technically possible to utilise the AC2 relay in a MultiPlus or Quattro to switch an AC load on/off (with the aid of an 'assistant' and some logic/wiring), but my preference/recommendation would be use a dedicated external relay/contractor for this.

For proper continuous power modulation, some form of DC PWM device (rated to the dump load) with external communication/control capability is required. Another alternative for DC dump load control may be to generate a digital PWM signal and then use that to drive a suitably rated DC SSR (solid state relay).

To modulate power on the AC side is harder, particularly with an inverter that is sensitive the the AC waveform being chopped up mid cycle (can cause the inverter to humm/struggle and lights to flicker). The My PV-AC Thor unit is able to provide a variable power/voltage AC output with a perfect AC waveform that won't effect the inverter and can be controlled via some in built/existing control options or externally via Modbus-TCP communication and your own/external control logic.

I agree that it would be nice if it was possible to create semi-complex condition rules within the Venus GX device menu - utilising relevant inputs from the system (such as the battery monitor and solar charge controller). But even this is not enough for a full/proper modulated power control system.

For this you may wish to look into Node-RED, which is eventually intended to be integrated into the Venus OS and will allow very complex control logic and automation to be created using basically any system parameter as an input. If your into basic programming, you can also write your own functions/logic directly.

If you are keen/interested in Node-RED integration, you can check out the current progress here; &

Finally - what parameters to use for the control logic is another very complex topic and there are many options to consider, either interdependently or combined - some parameters to consider are;

- Battery voltage (vs setpoint voltage)

- MPPT mode (Max power vs limited)

- PV voltage (vs PV MPP voltage)

- Battery SOC

- Battery current

- Solar irradiance

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Anders avatar image
Anders answered ·

Hi Mark

Thank you for you extensive answer

I would have no problem leaving the "logic" to a cloud solution (read VRM) for how much load my system can take to maximise PV power harvesting. My cabin has bin online continuously for 10 years and I do this harvesting manually.

I do agree that ideally a continuous measurement and variable load is ideal to maximise harvesting, but you can almost achieve the same with simple and inexpensive of the shelf Smart House Tech.

Some years ago I did investigate the DC power load option, but found it to complicated and expensive. For some years I used the simple option of turning the Multiplus on and off remotely (this was even before then CC GX arrived) I had a 500W electric heater turned on, and by switching on the Multiplus remotely I harvested 500W of energy that otherwise would have lost.

Today I use a slightly more advance system with several electric heaters remotely controlled by my Smart cabin system Telldus. I have:

- A 750W heater in the kitchen
- A 500W heater in the bath room
- A 400W heater in the guest room
- A 1000W heater in the hall
- A 250W heater in a small tech room

I do not think power modulation on the AC side is needed, it's sufficient with multiple loads of different sizes. I do agree that the Multiplus doesn't seem to like power modulations that well.

With these heaters I can create almost any load and maximise power harvesting as soon has the MPPT reach absorption. In some cases I turn them on early in the morning to secure a frost free cabin, and rely on the sun to back fill when "it" wakes up later in the morning.

I agree that there are many parameters and combinations of parameters available to trigger power load decisions. But my simple experience of manually turning on loads based on a few parameters tells me that this can be done with simple logic in the VRM portal. Potentially also within the Venus software but it's much easier for one cloud solution (VRM) to talk to another cloud solution (the Smart cabin) than achieving the same directly for a CCGX. The alarms in VRM can almost do it today, but they are not designed with this in mind.

  • If the MMPT is in absorption state tell me that via an email (can be done with alarms today)
  • The Smart cabin will turn on a load

  • Measure what happens to power consumption and harvesting of PV power.
  • If power harvesting goes up with more or the same as the load we are good - send me an email to apply load 2

  • The Smart cabin will turn on a load
  • Measure what happens to power consumption and harvesting of PV power.
  • If power harvesting goes up again with more or the same as the load we are good - send me an email of applying load 3

    and like this it could continue

    If the harvesting does not go up, or not enough, then turn of the last load.

If VRM even knew the power consumption behind each load (it could with some simple self learning AI) it could even decide which load to turn on or off to match available PV power.

As back up it would be possible to use the BMV to trigger a "turn off all loads" should battery SOC drop below 95%

The last parameter I use to day is weather forecast - but that probably to much integration to ask for.

I truly believe this is possible with some small changes to the alarm rules in VRM slightly more advanced than today, and a Smart Cabin system capable of turning on or off a simple AC switch.

I'll study the Github links Mark, but expect them to be to high end for my idea

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Anders avatar image
Anders answered ·

The Norwegian winter is slowly letting go of it's grip - the nice and bright spring sun shines and deliver lot's of energy - excessive amounts of energy. My daily consumption is in the region of 2Kwh with a Multiplus 5000W always on, some tech gadget, outdoor night lights a freezer and a refrigerator.

The daily production however is more in the area of 10Kwh, so a substantial daily loss unless I try to harvest - and that I do.

Piggybacking on my BMV 700 I have device informing my SmartCabin about SOC status, "full or not"?, and I control a manual switch, "Sun to day or not"

These to parameters then switch on 1500W og electric heaters heating the cabin. Not fancy but it actually works.

It would however have been much easier to make it much more advanced if VRM data would be available to smart home tech via IFTTT - anyone else out there also looking for this?

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