question

homestorage-77 avatar image
homestorage-77 asked

Force charge/discharge of Multiplus using VenusGX & Node-Red

What am I trying to achieve?

Charge the battery, or discharge the battery based on external input (via MQTT, but ultimately based on variable electricity tariff status)


I am up and running in Node-Red on the Venus GX 'large' image and am able to set the Multiplus to the following modes;screenshot-2021-02-09-at-140652.png

However if I set the multiplus to 'charger only' it obviously won't charge if I'm not in a scheduled charge slot.


If I set up a scheduled charge slot to be active at all times, then I can charge / not charge on demand by setting the 'Disable Charge' flag to either 0 or 1.screenshot-2021-02-09-at-142013.png

However when in the 'don't charge' state, it also won't discharge the battery as I'm in a scheduled charging slot.

I've tried setting the AC power setpoint instead of charging within a scheduled charging time, but it doesn't seem to do anything if I try the following;

screenshot-2021-02-09-at-142437.png


Can anyone offer any recommendations on how I can switch between charging or discharging to meet my requirement?


Multiplus-IIbattery chargingVenus GX - VGXNode-RED
screenshot-2021-02-09-at-140652.png (10.4 KiB)
screenshot-2021-02-09-at-142013.png (26.0 KiB)
screenshot-2021-02-09-at-142437.png (14.2 KiB)
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4 Answers
homestorage-77 avatar image
homestorage-77 answered ·

So I appear to have arrived at a solution by setting the ESS Grid Setpoint appropriately depending on my charge or discharge requirements.screenshot-2021-02-10-at-092905.png

If I want to charge, I can set this to 20,000 (which will charge my battery up to the 70A DC limit, assuming my AC loads are less than around 17kW - which is usually the case)


If I want to discharge the pack, I can set the variable to 0 and the system will behave in a normal way in that it discharges to match AC consumption.


It also gives me extra flexibility if I ever want to export energy, I could set it to -5000 and the system will do so, local usage aside.


It doesn't feel like the most elegant solution so would welcome any other suggestions, but looks like this will meet my needs.



screenshot-2021-02-10-at-092905.png (10.3 KiB)
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russ avatar image russ commented ·

Exactly what I want to do..

But no ess until I replace my multiplus with multiplus II.


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homestorage-77 avatar image
homestorage-77 answered ·

this has been one of those times where you go searching for how to do something, and come across your own question (and this time my own answer) from almost 2 years ago explaining how to fix it

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ronski avatar image
ronski answered ·

@Homestorage_77 I've also built a scheduled discharge in Node Red, did you run in to any problems setting the grid set point, or did it work as expected?

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homestorage-77 avatar image homestorage-77 commented ·

It largely works as expected, yes.


When in the state where the grid setpoint has been set to a high value, it discharges the battery at a nominal ~4kW (2kW per Multiplus).and there seems to be a lot of noise

screenshot-2023-03-31-at-185250.png


For example you can see here at 23:30 where the forced discharge began the power is noisy. At 0:00 where the scheduled discharge began, it became the usual smooth output.

I'm not sure why this is, however it works for my purpose so have never scrutinised it.

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screenshot-2023-03-31-at-185250.png (96.0 KiB)
andrew-penny avatar image
andrew-penny answered ·

Have you tried amending the "ESS minimum SOC" which on Modbus/TCP is address 2901.

Set it to 100% and you get the multi to charge, set it to 0% and you get the multi to discharge. This would be having no scheduled charging in the ESS, as you`d be building all of your schedules externally.

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