I understand how the function works in the ESS via Modbus.
The function in off-grid mode using the frequency is also clear so far.
But what happens if the grid fails? Do the ELWA 2 and AC Thor 9s automatically switch to frequency-based operation, or is the power still controlled via Modbus by the ESS when operating in island mode? Or not at all?
I’m also not yet sure whether the three-phase AC Thor can distribute the power across all phases, or whether one phase is driven up to 3 kW before the other phases are added.
I’m also wondering how well this works with an EVCS in the system. Which one takes priority, and how can this be configured?
Perhaps someone has already looked into this or has some experience?
I’m also currently looking into ways of “dumping” excess PV power. But I’m still right at the beginning of the planning process.
The explanations of the two models you mentioned left me with just as many questions. Apart from Victron, I don’t want to install a second “intelligent” system. As far as I understand it, you ultimately still have basic heating elements that convert 1 kW of energy into 1 kW of heat. The harvested PV energy is too valuable for that, in my view.
My current low-cost favourite: I’ll connect relay 2 of the Cerbo to the heat pump’s SG-Ready input. This will heat the domestic hot water above its normal temperature when there is excess PV power — using the heat pump’s sensible COP. The heat pump (in future) defined as an Opportunity Load, with a VM-3P75CT connected as the meter, and that’s it. Anyone who wants to can of course have fun with Node-RED: taking the grid status, minimum and maximum SOC, PV forecasts, etc. into account.
Stage 2 would be controlling the heat pump via Modbus (only possible using an additional heat-pump circuit board, and therefore at extra cost), but then it would also be possible to regulate the amount of energy used.
That way I would remain within the Victron universe, and additional loads such as EVCS and prioritisation would not be a problem.
I have the AC ELWA2 and am very pleased with it. I bought the immersion heater used for about half the new price, so €350. A heat pump would probably be considerably more expensive, and that would first have to be recouped…
The control now works directly via the Victron system and doesn’t require an additional meter.
What might be important when choosing the immersion heater is the buffer tank. I have a 750-litre stratified hygienic buffer tank. The immersion heater is installed in the middle, and it still has to keep switching off because the 75°C I set is exceeded.
Sometimes there’s a temperature difference of almost 10°C between the middle and the top.
What I’m getting at is that even 3 kW (limited in my case) can already be too much. So the 9 kW Thor will probably cycle even more, depending on the buffer tank.
I haven’t tested the off-grid function yet, but as far as I understand it, once configured, the immersion heater increases its power as the frequency rises in order to use up the surplus. This simply needs to be coordinated between the MP2 and the AC ELWA2.
Yes, I’m not sure about this…. For the ELWA, these are two different operating modes… does the increasing frequency simply take priority over Modbus here?
Now? It’s been working like that for ages.
These two pages date from mid-2019:
Incidentally, Victron doesn’t control the Thor/ELWA; the Thor/ELWA simply retrieve the grid-sensor readings from the GX device via Modbus and then try to regulate themselves to the configured grid value.
Off-grid, this is handled via the frequency. However, my latest understanding is that the frequency increase only works when the Multi detects that there is also a generator connected to its output.
The frequency settings on the Multi, Thor/ELWA and AC generator then have to be coordinated so that, ideally, the Thor/ELWA reaches (almost) 100% output before the AC generator reduces its output.
Yes, with the Inverter Assistant, or alternatively ESS with AC PV… An AC inverter is connected to the output; without this, off-grid apparently doesn’t work properly. I’m just not entirely sure whether the ELWA automatically responds to the frequency when it no longer receives any grid meter readings (in the event of a power cut). What also concerns me is how it works together with the EVCS.
I would argue that Modbus and frequency always run in parallel and, if in doubt, frequency has the higher priority.
You could basically test this quite easily by setting the frequency below 50 Hz in the Thor/ELWA settings; you can do this in 0.01 Hz increments.
You always have to test this a bit and adjust the values accordingly, but I think you can always achieve a good result.
You can set the feed-in power and a time delay on both devices (with the EVCS, unfortunately, only via a Modbus register in some cases).
So, in our off-grid system, it generally works quite well, because the frequency increase only kicks in relatively late. That means the AC-Thor is usually genuinely the last device to receive any surplus power.
In an on-grid system with surplus feed-in, this should work more easily.
You could probably also put something together using NodeRed that adjusts the thresholds in the Thor/ELWA when a car is plugged into the EVCS.
There is no documented register for dynamically throttling it from Node-RED in Victron mode. Control-Target is not exposed as a writable register. The only option is to set the ELWA to Modbus TCP mode and then write to register 1000 (power in watts). But that would mean handling the entire surplus calculation in Node-RED, which cannot be the point.
I didn’t necessarily mean controlling the Thor/ELWA differently directly, perhaps just switching it off so it doesn’t do anything for the time being.
No idea whether that can be done with the 1081.
But as I said, you can also start by playing around with the available settings.
Or switch the EVCS to manual for a few minutes when needed.
According to the documentation, this register must not be written to more than once a day.
That can’t be done via Modbus.
I don’t like experimenting on customers’ systems, especially not when I only have local access to the settings.
I had thought of that too, but switching from manual to automatic isn’t seamless. If the ELWA is too quick, it doesn’t work.
Actually, I expected the MyPV–Victron compatibility to mean that the whole thing would work without Node-RED and makeshift hacks, including with the EVCS.
As I said, my idea wasn’t to keep switching back and forth, and that shouldn’t be necessary anyway.
You can set a delay for that.
Alternatively, if you set a higher grid feed-in value in the Thor/ELWA, the EVCS could start even while the Thor/ELWA is heating.
It’s all a matter of the settings.
That’s something you have to clarify with the customer.
“Dear customer, in order to coordinate the system components optimally, it may be necessary to adjust a few more settings over the next few days.”
That’s what I always do when it’s more than a standard ESS.
My-Pv has a cloud service like the VRM Portal, which also lets you access the Thor/ELWA settings remotely.
As I already wrote, this isn’t active control.
The “compatibility” basically amounts to enabling Modbus on the GX, selecting Victron on the Thor/ELWA and entering the GX’s IP address—that’s it.
The Thor/ELWA then only retrieves the grid sensor values from the GX, and that’s it.
Even with a delay, you would still have to start it manually and then switch over, potentially several times, and if the EVCS pauses due to insufficient surplus, it won’t start again. Maintaining a grid feed-in of more than 4.2 kW (6 A three-phase) at the ELWA to enable automatic starting of the EVCS isn’t economical; that’s not what you buy controllers capable of diverting surplus power with watt-level precision for. So no, I still don’t see any configurable options.
That’s reassuring.
But I think any limitations when used together with an EVCS should at least be pointed out if it’s marketed this way…
Maybe the solution is staring me in the face and I just can’t see it. Is anyone running this with an EVCS?
I think you’re overthinking this and seeing problems where there aren’t any.
You don’t necessarily need 4.2 kW of feed-in power for the EVCS to start, as long as the system is allowed to use energy from the ESS battery as well.
“Allow battery/grid” or “Allow low PV power”.
That should allow the EVCS to start and automatically throttle back the Thor/ELWA so that the EVCS is given priority.
It really depends heavily on the particular system and how it’s used.
If the car is generally only plugged in to charge in the afternoon, the ESS battery and hot-water tank will usually be full, and all the excess PV power will be available to the EVCS.
As always, things will probably become difficult when the entire system (PV and ESS battery) has been sized very tightly.
As I’ve already written, this works quite well in our off-grid system, although that is also a rather specialised setup.
Unfortunately, we have hardly any on-grid systems with this combination that I could take a closer look at. The one system we do have is still under construction, so I haven’t got around to configuring it in more detail yet.
No one advertises interoperability between the EVCS and My-Pv.
I enabled that to avoid constant switching on and off. However, the effects of the settings aren’t really well defined. Yes, the battery is sometimes used as a result, but the charging process doesn’t start when the home battery is full but there is no, or too little, surplus available. “Waiting for Sun” — and if the ELWA 2 is already drawing 3.5 kW at that point, the EVCS waits a long time for the sun.
Unfortunately, the ELWA doesn’t have a remote input that could be used to switch it on either…. The system isn’t undersized (22kWp, 3x MP2 48/3000, 20kWh storage), but the ELWA will always be the first to claim the surplus because it starts heating at just 500W.
I don’t think I’m overthinking this…. If I plug the car in in the morning (Auto mode), the EVCS won’t start until there is more than 7 kW of surplus or the hot-water tank is full.
Perhaps someone here will find a solution on 24 September . This question has already been raised here, but unfortunately there was no solution.
???
Depending on the settings, the wallbox will also start charging when the battery’s SOC is above a certain level and the battery is being charged.
Do you already have a system with EVCS, or are these just assumptions?
With the upcoming opportunity loads, perhaps more could be done there as well.
Unfortunately, I haven’t yet had the opportunity to take a closer look at that or test it myself.
Is that so? I’ll have to observe it. But even if so… when the SoC is at 100% and there is no surplus left, I’m almost certain that the EVCS won’t start.
I don’t trust the whole thing; if it doesn’t work properly, the only option is to control the entire ELWA system with Node red. But as far as I understand it, the ELWA 2 controls via frequency in the event of a grid failure (both in ESS and in island mode), not in “Adjustable Modbus TCP”. The Modbus operating mode can only use Modbus, while the OFFgrid operating mode can only use frequency.
Yes, feed-in. I meant that the ELWA will probably dump the surplus before the EVCS detects enough power to start.
As I’ve written several times already, I’m fairly certain that it can be configured properly.
You may not find the right values straight away and may have to test for a while under different conditions, but I’m sure you’ll find the right values in the end.
If the Thor/ELWA is set to 500 W feed-in, the EVCS should start without any problems (provided grid/battery usage is permitted), because 100 W feed-in is configured there. You can also adjust a few values via Modbus.
That was just an example, but your idea could absolutely be the right way forward. If I set -300 W as the threshold for the ELWA and -150 W for the EVCS in register 5072, the EVCS would start and either bring the ELWA to its knees or partially discharge the battery.
At the moment, I have this battery/grid support enabled at the customer’s request…. Thank you, this is an approach that gives me hope. I would only need to set the EVCS threshold in Node-RED, for example, every 24 hours. I hadn’t thought of the EVCS registers—thank you for your patience with me.
. This question has already been raised here, but unfortunately there was no solution.