Feature request: Dynamic Grid-Setpoint in ESS, based on top SOC.

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geomz asked Jun 5, '20

Feature request: Dynamic Grid-Setpoint in ESS, based on top SOC.

Currently the Grid-Setpoint in ESS is a static number (in watts) that controls how much system power is allowed from grid, with the remaining load being served by incoming solar and/or battery capacity, down to a tolerable SOC. While that works great in the assumption of keeping batteries @100%, every day, it’s not so good for long-term health and maintenance of lithium batteries, in a (stable) grid-tied system.

I would like to suggest an upper limit to the SOC (other than default 100%), at which point the ESS would dynamically shift the load more/less (by changing Grid Setpoint) to charge the batteries when they’re below the high mark, and otherwise running the load off of solar or battery capacity, down to the existing minimum SOC (as normal)... or similar type of functionality.

Currently, I’m constantly changing the Grid Setpoint down, to serve the system loads from the incoming solar preferentially, as much as possible. Then resetting it up again at night, to keep the batteries above a reasonable SOC. While workable, it is way more manual than it needs to be.
I believe adding a simple top SOC to the algorithm that controls when to shift to using solar would greatly simplify and automate this process.

battery charging ESS SOC

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lucode commented · Oct 24, 2020 at 01:26 PM

Frankly I don't understand your suggestion. I suppose this paramter is meant to limit the power from Grid, to avoid an overload of the Grid connection. In my country there is a power limit in each contract with the utility which you allowed to suck from the Grid. If you overshoot this limit an automatic fuse shuts down your grid connection for a few seconds. I think what you like to achieve would better be solved in the area of the Min or dynamic SOC limit.

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nigelw commented · Mar 07, 2021 at 11:05 AM

There seems to be a growing number of people wanting to vary gridset point by time or automatically yet talking to Victron UK they seem to believe this isn't something wanted or in their development plans. They seem to have their head in sand somewhat whilst other ESS solutions embrace automation, Ifttt, Agile energy plans and agile outgoing. This ESS system is crying out for timed export settings and timed grid set point values plus SOC settings as you've mentioned.

I truly Hope Victron see the light and enable at least timed grid setpoint values.

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Alexandra ♦ nigelw commented · Mar 10, 2021 at 08:28 PM

Couple of notes on the lithium. All manufacturers of batteries never allow their cells to charge to full voltage. So even when your battery is 100% the cell is capable of taking more power. So that side is managed for you.

So when your battery is "100%" it really is 100% of what the builder of the bank is allowing you to have. So keeping your battery at 100 is not a problem at all.

Our systems are pretty automatic. We let them run down to a certain SOC every day and with battery life enabled will charge back up to 100% everyday and then cycle back down each night. If you dont set battery life then it doesnt prioritise charging the battery back up.

That being said ess has a dynamic control the current limit as it adjusts what it pulls from the grid when other conditons are met or not met.

If ess does not meet your needs then you need to look at other program options on the Victron. Or other options within ess to meet what you are looking for. Like not using battery life.

https://www.victronenergy.com/media/pg/Energy_Storage_System/en/controlling-depth-of-discharge.html#UUID-af4a7478-4b75-68ac-cf3c-16c381335d1e

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Modifications Space

Node Red Space

Answer 1 · 2022-10-05T13:20:00Z

positron answered · Oct 05, 2022 at 01:20 PM

I would also appreciate to have a dynamic grid setpoint mechanism on the Multiplus.

I try to explain:

With a GSP of 50W, the system will always get 50W from the grid, even if sun shines. So a remaining consumption of 1.2 kWh every 24h will be billed by my provider. Too bad.

With a GSP of -50W, the system will always push 50W to the grid, even during the night... which is a bit stupid.

So I would like to configure GSP = +50W if PV power is less than a defined threshold (example 400W) and GSP = -50W if PV power is greater than this threshold. So, during the day, the target is zero import and during the night, zero export.

Is it possible to manage this kind of dynamic grid setpoint with a script on the Cerbo GX ?

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nickdb ♦♦ commented · Oct 05, 2022 at 01:30 PM

You can only measure the power the PV is producing, not what it can produce, so the logic is near impossible to do without additional hardware.

It is easy to change the setpoint with logic using node red as an example. But to find a stable and predictable way to do it using PV measurements - good luck.

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positron nickdb ♦♦ commented · Oct 07, 2022 at 08:56 AM

Maybe my request was not clear enough, sorry. I just want to change the grid setpoint twice a day. Once in the morning when PV production is over a threshold (example 500W), then once in the evening when PV goes below this threshold. I don't want to do prediction.

If I set the grid setpoint to 50W (default ESS value), the system will import few electricity from the grid until the battery is full, even if PV produces 6000W...

Do you have information about node red solution ? Is there some API to configure the Cerbo GX with an external software ? Thanks

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nickdb ♦♦ positron commented · Oct 07, 2022 at 09:04 AM

Ok. Thats easy. Change to the venus large image, then use node red to create a time based flow with the ess control node to change the setpoint.

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positron nickdb ♦♦ commented · Oct 07, 2022 at 09:08 AM

I just found this web page:

https://www.victronenergy.com/live/ess:ess_mode_2_and_3

ESS mode 2 with MODBUS/TCP should be fine for me. I could control the grid setpoint and also manage battery charging time slots. Sometimes, it's better to charge the battery during the afternoon and export energy to the grid in the morning during peak hours...

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