Bart avatar image
Bart asked

Why can't I use ESS in off grid?

I would like to know what is the technical difficulty of having an off grid system running in ess mode. If ess can work as aback up for a week because of grid failure of one week, it is effectively running as off grid. So what would be the complication of that?

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3 Answers
Warwick Bruce Chapman avatar image
Warwick Bruce Chapman answered ·

ESS is effectively disabled on grid failure. Non-essential circuits go down and feed-in is disabled.

What feature of ESS are you looking for in off-grid?

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nigelfxs avatar image
nigelfxs answered ·

I cannot think of any difficulty or complication when running ESS in an off-grid system. The main issue is that all the nice features of ESS only work properly when you are connected to a grid.

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Bart,

It is not possible to run ESS in an off grid situation.

ESS mode requires the selection of a country grid code before the assistant will allow you to install it.

There is no reason to want to use ESS in an off grid situation either, all advantages require the grid.

There are disadvantages to attempting it too (e.g. by lying on the country grid code selection).

Different grid rules require a certain time of connection before disconnection on the AC input, and loss of mains detection algorithms. This can cause issues with generators.

ESS aims for a zero sum use of the AC input, and can allow power to flow back into the AC input in that process. Any off grid supply to AC input (e.g. a generator) is unlikely to behave nicely when power is back fed into it.

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Well one of the issues would be the frequency shifting. Range extenders and other equipment have some difficulties with 53hz. By my knowledge this is the only way to reduce the fronius output in off grid. The manual says not to use in off grid nor with generator backup. There must be a reason they say so. I would like to know why. Thanks so far

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I can see the use case, and it’s a neat trick but it is not supported, and I would instead suggest using DC solar if frequency shifting is forbidden.

An ESS system will still frequency shift if there isn’t an AC input to fix the frequency.

If your generator supplier is fine with AC PV being allowed to back feed into it, I would be surprised.

You could also run the AC PV into AC out 2, and then program that to cut the connection when battery voltage or state of charge reaches ~90%.

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Hello Guy,

Thanks, but see my reply above. And we generally use a contactor on the input of the quatro 't have it cut of when there is no power from a generator. Besides that this would be for bigger professional generators no problem. I just try to avoid frequency shifting an like the easy setup of ess

Thanks Bart

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In off grid if you are running a generator, it is because you want to charge the batteries.

With ESS, the system will not normally charge the batteries from the generator without further adjustments.

Installing an ESS assistant is extra work in commissioning. The units come and work off grid out of the box (though additional settings are usually required to optimise charging).

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Bart avatar image Bart Guy Stewart (Victron Community Manager) ♦♦ ·

I all understand that, but vê configure ess is not so difficult and lom b setting neither. You programma it with scheduled charging 24h 7 days and the generator will charge the batteries. This all would be a smaller problem then the 53hz to reduce the fronius. Or is there an other way to do so? Sorry don't want to be a pain in the ass. I just try to know why not and why yes

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Bernhard Matschinger avatar image Bernhard Matschinger Guy Stewart (Victron Community Manager) ♦♦ ·
Thank you Guy for this explanation..

I already have lot of ESS installations running perfectly. But when coming to Grid Losses due to power outages, some of my customers have a seperate 4 Phase (Grid 0 Gen) switch mounted on the input side of the ESS to disconnect Mains and connect to a Generator.
Yes, for me it is clear, that this does not work out of the box, becuase of enabled Backfeed and so on --> but is there a "Trick" a "Feature" to disable ESS on such Situations without reconfiguring the whole System --> like there is a Switch on the VenusGX, where you can set the AC Input to Generator.

I tried to use the system settings with disable Grid loss detection and setting the AC Input 1 to Generator, even deactivate backfeed AC and DC in the ESS Settings, but with a connected Generator the Inverter never switched to it.. It showes the Input Voltages and Herz on all 3 phases but never connects to it.

Is there something I have nod read in the Documentation or is it impossible to do so (Yes I know.. the Inverters do not know, if its a grid or a generator.. but isn't it possible to tell it to the system for this situations?). It is mainly for charging the batteries and supply excess loads due to grid failures for my custormers without going out to 50 installations reconfiguring them in case of power outages ....

Thanks in advance


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There seems to be a good reason to use ESS in my RV: I have a Multiplus, BlueSolar, CerboGX and lithium battery with two-signal BMS. (Stuart Pittaway's DIYBMS)

I have found no other way to stop the MPPT on cell-overvoltage except by enabling ESS.

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DVCC is what you need. ESS should never be used in mobile applications.

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candide avatar image candide Alexandra ♦ ·

Thanks for your reply Alexandra. The DVCC manual says:

"If DVCC is not mentioned in notes relating to your battery, do not enable DVCC."

The manual doesn't mention a two-signal BMS. Then how to set up DVCC? I experimented with it, but the MPPT never changed to "networked".

What's the disadvantage of using ESS in a mobile application is feed-in is disabled?

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The MPPT's need to be wired via (not smart networking) to the GX, they should reflect their state as external control.
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