Other way round. Negative is export, positive is import.
And yeah, if you have a grid-parallel installation, there is nothing the MP can do, but charge or discharge to achieve the setpoint.
quite some manuals Iāve read in the meanwhileā¦ 
Thatsa good question to ask - are you using a GX device, or do you talk with the multi through the mk3 interface?
I think this will also make a huge difference on how mppts are to be controlled.
Iām takling to the Venus system. Is it the GX device? Or ist the MPII the GX device? One must be to have ESS possibleā¦
Iām adressing /vebus/288/Hub4/L1/AcPowerSetpoint (or alternatively Modbus register 37) so obviously the MPII behing the MK adapter through the VE Bus. This way my setpoint is negative to feed power into the grid.
But why is that relevant regarding the control of the charge voltage?
As soon as I connect the MPII to Venus, the charge voltages get set to zeroā¦
Alexandra @lxonline ?! Are you still thinking about the answer or did you miss my question?
or is there nothing to sayā¦?
(Data Communication Whitepaperā¦)
so if I use Modbus - is it the GX device or the inverter?
The MPII does not ātalkā Modubus. so it must be the GX. But Iām addressing the device on/under vebus. So can anybody tell? And still: What difference does it make?
Hi @Philippoo
Yeah. I snuck it in there. This thread is busy. Sometimes a simpler approach is easier.
Some of your screenshots are different since you have tried different approaches. But so are the voltages set on the charger tab showing charger enabled and disabled.
exactly. I tried both. Both did not work, always chargers get diasabled (CVoltg set zero) no matter what I try.
also correct. this is why Iām going to connect the MP simply directly to my control system, not to Venus/GX/whatever anymore.
too bad. quite a nice system with fine options, but some stupid needless counterproductive āfeatureā makes using impossible.
for what reason an externally controlled inverter controls (disables) the mppt chargers??? this is a serious architectual mistake.
I think maybe it is more understanding how to control it. There are many who do externally control the system. They just arenāt sharing their secrets here.
Victron documentation is really extensive. If it is a secret how to make an externally controlled inverter not to destroy the functionality of a PV system, then it is simply rubbish.
No, the GX device is a external device (different kinds, cerbo, pi, color control, ā¦). There is also the Multiplus GX, which has a GX build in.
Usually the GX will orchestrate all devices connected. BMS, multiplus, mppt chargers - everything.
I think it would be super helpfull to draw a schematic, which devices you have and how they are connected, including your second/primary system.
It is very frustrating to get information about your layout āstep by stepā. Itās like consulting on how to replace the engine oil, but then figuring out you have an electric vehicle
āinformationā:
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my āGX deviceā is the Raspi with Venus on (comparable to a Cerbo but some fewer interface harware)
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up to 7 SmartSolar MPPT chargers are connected via VE.Direct.
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the SmartShunt is connected via VE.Direct to the Venus Raspi.
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the JK PB BMS on the battery is connected via CAN bus to the Venus Raspi.
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MPII communication: VE.Bus-MK3-USB-Venus Raspi (this will change today to get connected to the main Raspiā¦)
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Lumentree communication: RS232-USB-āmain control Raspiā
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my control communicates to the Venus by MQTT over network.
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grid power info is taken from the official grid meter, connected to my āmain control Raspiā
āenergyā:
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the 280Ah 48V battery is the dc link between chargers and inverters.
it also sources the low-voltage heating of domestic hot water. -
DC of chargers connected to the battery
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DC of the inverters (Lumentree and MPII) connected to the battery.
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AC of both inverters is connected to the grid (only).
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all AC loads connected to the grid (only)
thats it.
ok, there are two Raspis doing control stuff, one close to the Venus/Victron/Lumentree/battery and one downstairs in the basement close to the heating unit, but this is not of importance. simply take it as āthe external control systemā linked to Venus via MQTT.
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surplus is detected utilising the MPP OperationMode of the chargers.
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charge control is done by determining (limiting) the charge voltage according to the SoC reported by SmartShunt
(this is also a reason why it is unacceptable that ESS assi controls the charge voltage, but may be āoverruledā by controlling the charge curve parameters dynamically - but it doesnāt work anyway, it is fixed zero, uncontrollableā¦)
basically a very āsimpleā system architecture, working perfect.
I can determine PV surplus regardless of the SoC level. so I can keep the battery at 80/85% or whatever and draw full power from the chargers nevertheless. Impossible with any ESS assistant (even they could, but itās not implemented) ā¦
I can split PV power for parallel charging and/or heating and/or feeding-in - very verastileā¦ up to now I have not seen this being realized with ESS assis. perhaps I missed something
speechless? ok, I will start doing something āproductiveāā¦ 
by the way - all this is not of interest when looking at the initial basic question:
What to do to avoid GX/ESS-Assi disabling the PV chargers when using ESS Mode 3 ?
Not speechless. I was living my lifeā¦ I have a family.
Obviously i am not familiar with whatever custom control loop you have made.
Are you using the AC input as the mode three documents say?
I know guys who are achieving what you want to do using node red. Since you can manipulate set points and charge current etc from there.
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