Reduce Charge Power

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diederik asked Mar 29, '24

Reduce Charge Power

Hello,

I'm new to Victron, ESS and Node-Red, so sorry if I ask stupid questions.

For the next winter I'm looking for a way to limit my grid power to 2500W. When the load in my house is low, I like to charge my battery to a certain level. But the total power from the grid must stay under 2500W.

I'm building this up step by step. The first step is to control the grid power.

As you can see on the bottom right there is something wrong with my calculation. The maximum charge power is to high. The battery would charge at 2526W.

When removing the wire from above the calculation works but the result is negative. Now idea how to do this calculation right.

Any help for this first step in a bigger project would be welcome.

Thanks.

ESS grid victron

charge-test.png (68.5 KiB)

charge-test-2.png (41.9 KiB)

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Modifications Space

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Answer 1 · 2024-03-29T10:40:19Z

nickdb answered · Mar 29 at 10:40 AM

You would use the vebus node and set the input AC current limit (in Amps) if you wanted to restrict grid usage.

If you aren't exporting, you can use the settings node and set the DVCC max charge current to limit battery charge, this will also limit max DC PV production. If you are exporting, this parameter is ignored.

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Answer 2 · 2024-03-29T11:20:45Z

diederik answered · Mar 29 at 11:20 AM

Thanks for the tip.

I would like to be able to dynamically adjust the limit. So this leaves me with the problem how to calculate the maximum.

Let's say I'm using 4A in my house, I want to set the limit on 10A from the grid. The maximum charge current would be 6A.

But these numbers are changing every time.

The idea is that I want to keep my battery on a certain level. When I use more then 10A, the extra power should come from the battery. It's called Peak Shaving I think.

Possible?

1

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diederik commented · Mar 29 at 02:22 PM

Looking into this a little deeper. I hate Javascript but I found out this is the proper way to do it. Working with flow or global variables should fix this.

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Answer 3 · 2024-03-30T07:31:40Z

jason-lane answered · Mar 30 at 07:31 AM

Did you work it out? I think the following overview should give you a good start. Whenever the load value changes, it will recalculate. You might want to limit this, however, so it's not re-calculating and changing every second. eg. You might want it to re-calculate only every 5 minutes, or only if the change in load is bigger than a certain amount.

screenshot-2024-03-30-at-31943pm.png (47.1 KiB)

screenshot-2024-03-30-at-32037pm.png (46.8 KiB)

screenshot-2024-03-30-at-32111pm.png (82.9 KiB)

screenshot-2024-03-30-at-32331pm.png (72.6 KiB)

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Answer 4 · 2024-04-03T06:00:21Z

diederik answered · Apr 03 at 06:00 AM

Yes, I'm almost there. When ready I can post it here.

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