question

rotortalk avatar image
rotortalk asked

Can I control the AC-Input relay via an aux input?

I have been looking at all the assistants and the Virtual switch but I cannot find what I am looking for.

Is it possible to switch the AC-Input ON and OFF by using the Aux Input? I'm in the UK and only want to take grid power when it is cheap or I need it. The cheap (Octopus Agile) tariff is not a fixed time, so I want to be the one (well, a Pi at least) to control when I can take energy from the grid.

I was planning to use an external contactor to shut down the grid connection, but since there is one in the Quattro it would be nice to use that.

I think I could achieve a similar thing by using ESS and forcing the charge rate to 0 on a signal on the aux input, but it doesn't feel quite the same...

MultiPlus Quattro Inverter ChargerESS
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4 Answers
shaneyake avatar image
shaneyake answered ·
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wkirby avatar image
wkirby answered ·

The backfeed relay is a safety component, it cannot be externally controlled at all.

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rotortalk avatar image
rotortalk answered ·

I have to disagree, because it can be controlled by the Virtual Switch and conditions such as Load or Battery Status which are not safely conditions. i.e. Ignore AC input until the load is more than x. This is perfect, I just want to add a condition, "Ignore AC input unless Aux 1 > 2v"

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wkirby avatar image wkirby ♦♦ commented ·

Those VS conditions are internal conditions.
What I meant before was that there isn't an option for direct external control of the backfeed relay.

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rotortalk avatar image
rotortalk answered ·

@shaneyake - that is perfect. Thank you! My searching skills weren't good enough.

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wkirby avatar image wkirby ♦♦ commented ·

To be fair to yourself, Mark only posted his solution a few hours ago.

I did not think about doing it that way. I have tested it on my test setup and it works!
So, my apologies but at least I have learned something new today :)

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rotortalk avatar image rotortalk wkirby ♦♦ commented ·

Yes, I saw that. It seems we both had the same question at the same time! I'm super happy it works. One less piece of hardware

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wkirby avatar image wkirby ♦♦ rotortalk commented ·

I'm curious on how or what you are querying to know when the lowest Octopus rate is active?

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rotortalk avatar image rotortalk wkirby ♦♦ commented ·

I don't know where you are based so I hope I'm not teaching you to suck eggs, but Octopus Energy in the UK has a tariff that is based on the wholesale price of electricity which is a first for us (I only learned this week, after reading horror stories of huge bills in Texas following the storm it seems common in the US)

So Octopus publishes the next 24 hours pricing at roughly 4pm each day and it is available via an API on their website, so it is a trivial call (in my case using a Raspberry Pi) to their server to get the prices, broken down into 30 minute intervals for the next 24hrs. Then, combine this information with the state of charge of ones batteries, the weather forecast, also broken down into 1/2 hr intervals to predict the solar output and you can optimise what little you take from the grid at the appropriate time. If solar isn't going to cover you for the next day, load up at night!

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wkirby avatar image wkirby ♦♦ rotortalk commented ·

Thank you for that information.
I am UK based. Once I get my Consumer Unit replaced and have the facility to use stored energy for house loads then I'll consider something like this.

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shaneyake avatar image shaneyake rotortalk commented ·

@rotortalk Yeah, I only saw your question after I posted mine.

You can now do all this processing in NodeRed on the Venus or Cerbo GX if you have the large firmware running. Then use the relays on the GX to trigger AUX input. I am doing something similar for deciding if power should go to battery, hot water heater or get exported based on solar and weather forecast. I am based in South Africa and we don't have dynamic rates but the grid is super unstable in the mornings 6am to 8am so trying to get the system to stay off-grid during those times because it sometimes trips the inverters in Overload because of LOMs. At some of our installations I want the inverter to disconnect when the site switches to generator for a similar reason.

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