question

klandos avatar image
klandos asked

Multiplus goes into Passthru when AC-IN overloads

Hello,

I've a system containing 2 Multiplus II 5000, a couple of MPPT, Cerbo GX and Pylontech batteries.

The system is configured as Single Phase parallel System and all load is connected to AC1 out of the Multiplusses.

PowerAssist is active and also a AC Input Limit of 30A is configured through VictronConnect (with MK3 Adapter).

ESS Assistant is loaded onto both Multiplus.

ESS Mode is configured without battery life with a minimum SoC of 20% in the Cerbo.

Every device updated to the newest Firmware.


When the SoC goes down to 20% the Multiplusses start using energy from Grid. They are in Bulk mode.

That's what I expected.

Problem:

When the AC Load is higher than 30A the Multiplusses go into Passthru mode.

This is what I don't expect.

What I would like instead:

When the AC load is higher than 30A the Multiplusses should use 30A from AC-in and use the rest from the Battery. When the load is going back under 30A the Multiplusses should fill up the batteries back to 20%.

Multiplus-IIESSpowerassist
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6 Answers
tnt369 avatar image
tnt369 answered ·

you can smooth it by starting at a little higher SoC (25%?) and reducing the factor (500 seems pretty high). Also i recommend to add a fix value to the setpoint (i.e. 1000W) while charging (as minimum).

  1. Example: gridpoint=$(((25-soc)*200)+1000)


I also recommend to limit the setpoint maximum to i.e. 5000 to prevent grid from overload.

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Although this is not the best answer I expected this is what works for the moment. A raspberry changes the grid point at lower socs to achieve the goals.
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kevgermany avatar image
kevgermany answered ·

If SOC is over 20%, it should work as you wish. But once it drops below 20% there's no power assist because you set minimum SOC to 20%.

Or have I misunderstood?

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If SoC is over 20% the complete Ac Load is driven by batteries and Grid is at 0 Watt as it should.


I thought I could you the last 20% as a buffer for the "weak" AC Input if load is more than 30Amps.

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klandos avatar image
klandos answered ·

Hello,


Reading this:

https://community.victronenergy.com/questions/118301/powerassist-in-ess-system-development.html

my goals seems not to be possible.


As victron is a "Swiss army knife", how can I achieve the goals?

My first thought was to set the grid point to f.e. 5000 Watt. Problem is that due to enabled DVCC I cannot Limit Charge Power from Multiplus to disable charging from grid.


Would it change anything if I use Generator as AC-IN?

Is maybe ESS the wrong assistant and I should run that installation without?

Which settings?


I really cannot believe that my use case is that unnormal that there is no option to achieve:

- use MPPT to charge batteries

- all loads on multiplus ac1 out

- when soc below 20%, keep batteries at this level except when there is grid failure or the AC IN1 limit is reached (power assist...)

- I don't want to feed back to the grid



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tnt369 avatar image
tnt369 answered ·

I have a similar constellation. I solved it by connecting an external controller via Modbus. I have set the Soc minimum to 10% in ESS. The external controller reads the SoC and controls the Grid Setpoint (from 30W to 4000W) so that there is always at least 20% in the battery.

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Thanks for your idea, you use register 2700 on ID 100 for that, right?


I would prefer an internal solution without external controlling if possible.

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Right. Reading SoC from 843 and writing setpoint to 2700. All unit id 100.

For me is a good solution because with the external unit i also control a part of the load (i.e. charger of the car).

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Based on your idea (thx 4 that!) I made a 5 liner bash script on a pi that runs every minute, reads the SOC and sets a new grid point:


..read soc
if ((soc > 19)); then
gridpoint=60
else
gridpoint=$(((20-soc)*500))
fi
..set gridpoint

resulting in that grid usage over night:
gridimport.png


Depending on Soc the grid import goes up and down and the soc is somewhere around 17% all night long catching up spikes in the evening.

Power assist as its announced isn't used at all....


I still would really prefer a "official" way rather than this "hacking" method which on top definitely won't have a good efficiency. Maybe a Victron guy could leave a statement or advise?

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gridimport.png (370.8 KiB)
tnt369 avatar image
tnt369 answered ·

Another option is to reduced the charging current (DC) to a low value (approx 15A) so you can set the setpoint to a high value (fix, i.e. 5000W) and the system charge slowly with approx. 800W.

If the load goes higher (than the setpoint) the charging reduces. And if the load goes more higher the battery will discharge to assist te grid.

Switch on that high setpoint if SoC is lower than 20% an switch it of if SoC over 25%. So it will not cycle so often over the night.

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klandos avatar image
klandos answered ·

I would still like to have a "official" answer from victron how my goals are possible without third party controls.


On top I have 2 other problems:

- When the battery is full enough (f.e. 70%) and the AC load is going higher than f.e. 8000 Watt for a longer time (2 Multiplus 5000 parallel), the system does not use AC In on top but goes into passthrough, using 8kW + from the grid and nothing from the battery.


- No feed in is configured, see the picture, there is often a bit feed in that is not allowed.


cerbo.png


Again, is ESS maybe just the wrong option for me and I should disable the ESS assistant und configure AC In as "Generator" even if its Grid connection?


appreciate any thoughts!


cerbo.png (46.8 KiB)
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No one Any advise?


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@KLandos

You can use the grid as a generator.

Configuring the system to connect under certain conditions like load and state of charge.

Just remember for load based conditions the system may take up to 30 seconds to synchronise and connect.

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klandos avatar image klandos Alexandra ♦ ·
Thanks for your answer!

If I understand correctly I should disable the ESS Assistant at all and just use Generator as Input even if its grid. With Option to connect only if soc is lower than xy f.e.?

Or should I decide to use a contactor to active disconnect the grid from Multis AC In?


There is a third 5000er on the way for being in parallel to don't have any problems with ac overload in future when battery is full enough.

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Peak shaving is not supported by ESS as this time.
This is possible by using NodeRed running on the GX, this feature is currently in Beta.

All grid-tie inverters will have a constant push-pull with the grid so you will always get a little bit of feedback when a big load is turned off.

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klandos avatar image klandos shaneyake ·
Yes… for me that case is solved, but Just because I have no grid anymore and no ESS assistant loaded. For Winter I‘ll use a genset when needed.
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