Victron API to determine excess solar power availability

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gyrovague asked Aug 31, '20

Victron API to determine excess solar power availability

Is there some way to determine when excess solar power would be available (ESS, with no grid feed-in)? For instance, when SOC is 100%, the solar yield generally drops down to just enough to satisfy the current consumption, even when the sun is still shining brightly. Of course it must do this, because the energy has nowhere to go... However, I'd like to make something (maybe using e.g. a raspberry pi zero W) which queries the Victron in some way and lights up an LED when such excess would be available, so that I can then turn on (manually for starters) things that aren't "necessary" but would benefit from free electricity (e.g. pool pump, or electric geyser). Similarly, I'd like to show another LED for when energy is being used from the battery, so that one might also opt to turn off (or not turn on) less-necessary things in those circumstances, and yet another LED to show that the grid input has failed for instance.

Hoping there exists some simple API which can give this information :)

VRM

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suttridge commented · Aug 31, 2020 at 09:48 AM

Hi there,

I will just put this as a comment, not an actual answer. I am going to be doing something similar in the near future. Basically, there are two methods that can be used :-

1. Use an irradience meter connected to the Venus device (see the Victron manuals for this). You can read this value from the Venus device, and knowing your panels' capability, you can work out the potential excess power available - thus you can estimate how much extra load can be switched on (or off).

2. While monitoring the system, you can just switch on extra loads until the battery starts to be used again, then you know you have reached the limit of the excess power being available. It is a bit trial-and-error.

There are really no other ways of doing this, since it is all about know the possible power that is available from the solar panels at any time.

Best regards,

Steve.

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gyrovague suttridge commented · Aug 31, 2020 at 06:57 PM

OK, thanks for the comment. I more or less suspected this would be the case, but was hoping perhaps there is some info from the MPPT or so that could somehow indicate it is drawing less from the panels than would be available.

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suttridge gyrovague commented · Sep 01, 2020 at 06:55 AM

Yes, it's unfortunate, but the MPPT cannot tell you this.

Steve.

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Meine_Energiewende gyrovague commented · Sep 01, 2020 at 07:14 AM

I use a "Fronius" inverter .... this in inverter is in the state "throttled" if there is more solar power then the ESS is able to use. Maybe victron can implement something like this in their own firmware.

I read this status via MQTT and switch on/off several devices.

Jens

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gyrovague Meine_Energiewende commented · Sep 01, 2020 at 10:17 AM

Yes, the "throttled" thing is what I had hoped I'd be able to query from Victron in some way.

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ewalderasmus answered · Sep 01, 2020 at 07:00 AM

Hi @gyrovague

What is your system made up of?

The reason I ask is that this can be done using assistants. You will need to have an assistant to both turn on and off both relays (ie lights). But this is not very hard.

How I envision it working is:

- During daylight hours*, if the battery goes into absorption** one can safely assume that there is excess solar power available and you can turn on your extra appliances.

- if the battery SOC drops below 95% then you can safely know that the batteries are being used to power the load and hence you can turn off those appliances.

* because your system has no grid connection, I can only assume you only have solar to charge the batteries meaning that whenever your batteries are finished absorption then you are in daylight hours...

** you can change this to bulk finished if your batteries have a very long absorption period.

This can all be automated rather simply if you want, but just ask if you want my 2c on that as well, but if you only want some lights to turn on, then that can be done in a few minutes using different programmable relays.

Attached are a few screenshots which can help, I have looked at the excess energy scenario, and made programmable relay k1 turn on when absorption is finished and the state of charge is higher than 95%, This is only the turn-on state...

Hope this Helps

Regards Ewald

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Modifications Space

Node Red Space

Answer 1 · 2020-09-01T07:05:20Z

gyrovague answered · Sep 01, 2020 at 07:05 AM

Thanks @EwaldErasmus, I will take a look at that. I have grid-tie (but no feed-back) Multiplus II 5000 in ESS configuration, with Victron 150/100 MPPT, 4x 3.5kWh pylontech, Venux GX.

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ewalderasmus commented · Sep 01, 2020 at 07:29 AM

Hi @gyrovague

In that case, you will probably have to play around a bit to see what you can do. But I am sure you can use the assistants to do this. You probably can get away with one programmable relay just using the NO and NC options.

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dunnp commented · Sep 01, 2020 at 11:14 AM

Just a thought - if it is a SmartSolar 150/100 you could use the in-built relay to switch your load when the MPPT goes into float. No relay in BlueSolar model though.

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Answer 2 · 2020-09-01T12:07:32Z

Mark answered · Sep 01, 2020 at 12:07 PM

There are many parameters that can be referenced/options to determine if there is excess PV available and a number of possible control options.

If you are only interested in a simple on/off control logic, the best option would be to look at the following MPPT solarcharger parameter:

solarcharger/MppOperationMode

This path identifies if the MPPT is producing maximum power or if it is being purposely limited.

You could read this via Modbus TCP and setup some kind of external control system, but the better option would be to consider using a recent WIP/beta Venus 'Extended Image' FW build that includes Node-RED. Beware that this is still in the test phase and not officially supported by Victron. You can download and find out more here: https://github.com/victronenergy/venus/issues/378

Node-RED is extremely flexible and powerful - allowing complex (or simple) control logic to be easily setup. You can create a suitable logic based on any available dbus path/a combination of paths and various conditions to directly control a relay on the GX device.

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