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DanievS avatar image

How can I disconnect the grid in an ESS system?

I have MPPT 150/85 with Inverter Quattro 8KVA and SuperCap batt of 7.1KVA. System not setup to put power back into “Grid”. ESS is enable and setup to only run on “Grid” when batt is depleted. During day the batt charges to 100% and at night the batt is drained until 5% is left resulting in switching to “Grid”. Next morning the PV’s kicks in charging the batt. Once SuperCap batt is on about 85% the Grid will be dropped and system switches to solar power. My question: I would like my system to switch off Grid when batt is charged up to 30%. Reason being is that I have sufficient PV power to both run the household and charge the batt at the same time. My installer informed me that due to the way a SuperCap batt operates it is not yet possible to modify switch over setting. Regards Danie

ESSgrid
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I overlooked to mention that any advice or suggestions will be appreciated.


Regards

Danie

Hi, I guess this can be don't via programmable relays. Us K1 od (K2) and relay switch with sufficient Amps - for the AC-IN ( and which can accept the voltage of your batteries of course) and then program the relay to NO/NC to the desired level for SWITCHING OFF and SWITCHING ON the relay. You will need two programmable relay assistants.

Have we got an exact answer from Victron on this. I have estimated I am exporting 350kwh of electric each year and I could be saving this just by disconnecting from the grid when my battery is in the 15-95% range.

7 Answers
ejrossouw avatar image

@DanievS I would be interested to know what settings you have. My MP II with 8.8 LG Resu typically "disconnects" grid when it reaches the min SOC plus 5%. Also, the reverse is true in that the battery is only charged from grid if it falls below the SOC to maintain min SOC. The MP II connected parallel to the grid with nothing wired on AC1 OUT. During the day it will charge battery using PV only until it reaches the min SOC + approx 5%, while grid services house. Once this level is reached, the PV serves house and continuous to charge battery with grid reduced to zero. What is your sustain voltage?

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Daniël Boekel (Victron Energy Staff) avatar image

Hi @DanievS

This is probably done in the inverter, using an assistant.

Why Exactly this cannot be changed with your batteries I don't know.

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ee21 avatar image

I hate to be the bearer of bad news, but the ESS Assistant module is not intended to be used in this manor, nor do I think there is any way of accomplishing this except by manually disconnecting the AC-Input using some sort of relay switch. The ESS manual in fact specifically says not to use it for this:


When not to use ESS

  • Off-grid systems - either with or without generator.

  • Marine systems.

  • Automotive systems.

  • Inverter priority, also known as 'Intentional islanding“ or 'Ignore AC' input systems.


By default, and unless there is some trick I am not aware of, when running ESS you are always "on-grid" as long as the AC-Input remains active. This is just a fact of how this feature works.


If you have your grid set-point at 0W though, and sufficient PV, battery and inverter power, then there is no reason that 99% of your AC consumption should not be coming from Off-Grid. You should be able to see in the VRM portal depending on how the system was setup, exactly how much is being taken from the grid throughout the day.

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Russ avatar image

Just an interested observer here, but I think your main requirement from above is to not export your excess pv to the grid, rather self consume, even to the extent of having low Soc in the evenings.

Can't you just set for zero export? You will I think need a grid meter to allow that..

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Jan Zmrhala avatar image

Hello, try to use the K1 or K2 relay. Program it to close/open when the state of charge is at the value you are looking for. Than connect external relay switch (the voltages and Amps depends on the used inverter) and use it to connect/disconnect the grid. Is it clear?


You will newd just one more relay and thats it.

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jsmvanwyk avatar image

Hi,

I saw another post the other day that was indicating it might be possible to use the Generator Flag to ignore the AC input. I'm not sure however if one can run this and ESS at the same time. I've not tried it but it might be worth looking in to? Here's the link https://www.victronenergy.com/live/assistants:ignore_ac_input_using_the_generator_assistant


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DanievS avatar image

Thank you for all the advice and suggestions, appreciated.


To clarify some of the points mentioned:

1. SuperCap batt is only charged from PV's and not Grid. This is how I want it to be. When batt is at remaining power of 5%, the system switches to Grid - this typically only occurs at night.

2. During the day I have ample spare PV capacity to more than fully charge the batt.


The issue is that in the morning when the PV's starts to provide power, I could be off the Grid sooner, instead of the system remaining on Grid until the batt is just about fully charged.

The household power demand must get priority over the charging of the batt when there is sufficient PV power available to run household demand. Thereafter, once there is excess PV power, only then should it be utilised to charge the battery.


I am also of the opinion that there should be such a setting on the inverter - just a case of where. Victron is after all the best!!

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