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franklouwers avatar image
franklouwers asked

API to define scheduled charging

Hi,

A lot of European countries are moving to differentiated electricity prices. On a warm, sunny, windy day, electricity will likely be extremely cheap (or even have a "negative price"), while a cloudy, cold later afternoon with no wind likely leads to very expensive electricity prices.

Having PV panels and a battery makes you probably independent of this in the summer, but I want to leverage our Victron (Multiplus + GX) system to once a day download the "tomorrow" pricing scheme, and program the system to load the battery from grid when power is cheap so my battery is full enough to not have to use grid-electricity when the power is expensive.

So question: how do I start? I was hoping to be able to use the API to program the charging schedule, but that doesn't seem to be the case? Alternatively: is there a way (API / MQTT / ...) to signal the system to charge from grid "now"?

Additional question: if the system is on "Scheduled charging" mode, and in a time-window where it is not supposed to charge, but my PV production is higher than my current load, will it charge the battery from PV during that window?


Thanks!

battery charging
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Jason - UK answered ·

@franklouwers Im in the process of putting together controls system doing just that. Using Node Red, I can take the predicted solar generation in Mj, converted to kWh form a weather API. If I can then find a way of extracting the SOC from my multiplus and converting that to stored kW, then I know how much to charge the battery to. Once I know how much I know how much to charge the battery to, knowing the charge rate on my Multiplus (3.3kW/h), I divide the number of kWh required by the charge rate to work out the number of hours. Then taking the number of charger hours required, I take the API from my energy supplier (Octopus Agile) to work out the cheapest number of hour required to charge my battery to 100% and then charge my system on that basis.

Its a work in progress and a learning curve for me as Im new to Node Red but the plan is to create a controls strategy that charges my batteries as little of the grid using the cheapest half hour per day and taking into account the predicted solar generation to bring the batteries to 100%.


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franklouwers avatar image
franklouwers answered ·

Can Node Red instruct the system to charge from grid?

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Jason - UK avatar image Jason - UK commented ·
Yes. In short it would operate like a standard ESS set up but the charging would be dynamic depending on what periods in each day would be the cheapest and it would calculate the number of hours required to charge the system to 100%.
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sieade245 avatar image
sieade245 answered ·

@Jason - UK Hi Jason. Did you get anywhere with this? I'm looking at doing similar, same setup as you with solar/ battery. Only difference is I have 6 hours cheap rate fixed from 23:30 to 05:30 each night so want to use the forecast to try and limit my overnight charging to take into account the solar gain the next day.

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