Multi Plus2 ESS AC grid charging when it shouldnt.

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ty-web asked Aug 4, '23

Multi Plus2 ESS AC grid charging when it shouldnt.

Hi

I am trying to set up a self consumption system, with the PV being the only thing to charge the batteries. However last night the battery got down to 14% and the Grid took over the load as expected but it also started charging the batteries at full charge rate (50Amps) drawing 4kw from the grid(my max 20amp setting in the multi for the grid connection) at a SOC of 20% I shut the AC off. I though it ight try to raise the battery to 16% due to battery life or some other battery preserve setting, so I let it run for a bit.

Setup: Multiplus2, A Fronius Primo 4500w on AC out, Cerbo GX. At present I only have one 5kw pylontech battery hooked up through can bus as I am trying to get this functionality to work, and my wifes car takes about 7kw after a trip to work and back. During this testing this is the only load on the system.

This morning with the PV charging the battery I turned back on the AC grid and soon after it returned to full charge rates on the battery again, with zero load on the output, PV was about 500wats at that time.

I have ESS turned on, min soc is 15%, No feed in to grid is allowed, all internal metering, M2 on the VE bus, battery on the Can bus to the Cerbo, Fronios via cat5e network.

I am sure I have missed a setting some where but I cant seem to find it. I have tried both "with battery life" and "without" and this is not changing the AC recharging the battery.

How do I stop the M2 from charging the battery from the Grid?

My Anticipated system setup is:

Self consume all PV power produced during the day time and at night for the entire home(minus the EV which is on a grid timed circuit), when the battery reaches min SOC set point, grid powers all loads until such times the PV is able to take over and supply loads and battery charging. Night time base load in the quiet hours is aprox 600w, peak in the morning is around 1.5kw, and around 2kw during the evenings. I have calculated provided we have a nice sunny day the 20kw battery should be sufficient as a starter to get through the 16hours of insufficient PV. I may need to increase the PV array but it will be via MPPT not AC coupled. This was a retro fit to existing so it made sense to keep the AC coupled.

ess settings

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matt1309 commented · Aug 04, 2023 at 12:48 PM

Hi @Ty_Web

Potential things to check/my guesses:

1. ESS assistant settings are correct and setup on the GX device with multiplus showing up as a device under the devices list on GX device.

2. ESS not set to keep batteries charged accidentally?

3. Is ESS set to with Battery Life? If so min SoC may be increasing overtime hence why the the system was charging up from 14% to 20% or higher (this sounds most likely based on what you've described)?

4. Scheduling charging is enabled in ESS that may be causing it to occur?

5. (less likely) Minimum voltage was hit rather than SoC and the plyontech cells are calling for charging to bring cells above min recovery voltage (Can't imagine this is the cause as there'd likely be alarm notifications on the system/gx device).

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Answer 1 · 2023-08-05T02:41:22Z

Thanks for the reply, I have confirmed as above suggestions that all is as I believe it should be. I think there is a bigger issue here with my settings or how I have implemented the ESS assistant in the M2. Yesterday I turned on the AC supply to the M2 after the PV(ac coupled on out1) was already charging the batteries and had bought them up a couple %. The PV dropped out when the M2 synced to the grid. Thats ok sort of expected that, the PV came back on line after the 2 min warm up time, and dropped out about 30 seconds after supplying power, this repeated three times with the PV not being able to stay on the "Bus" so to speak with the grid, batteries where aprox 30%. During this time the Grid was charging the batteries at the 50amp rate the grid was limited to, the battery charger setting in the M2 is set to 70amps, so there was still head room for the PV to assist.

In frustration I switched of the AC grid and modified it with a contactor, driving it by the GX using the Generator function, with the criteria of SOC, Temp, and Load. The Grid is only used during the night after the battery runs out during this test phase. In my current testing I am just using the whole system to charge the EV. The system did as it should in this scenario, when soc got to 17% it enabled the grid (generator), which supplied the load and about 400watts to the battery. The Generator went off when the battery got to 20% SOC the process repeated once more during the night as the car took 7.5kw from the 5kw battery. This scenario is ok as the PV inverter is not available over night. However in winter with low sun days the Grid will likely be on supplying loads and I want the PV to come on and assist. Maybe I need to try dropping the ESS and going to Hub 1 or 2 as this may perform better.

Any hints on what might be causing the PV to keep dropping out. The system is set to NOT export, I did briefly change this but it made no difference the third restart was with this function enabled, it didnt make any difference. When the PV tried to reconnect on both the secondary occasions, I noticed the Inverter was in "External control" according to the GX. Is this likely the cause, I want it to stay in inverter all the time for self consumption. I cant seem to find a setting for this.

Answer 2 · 2023-08-07T10:13:46Z

matt1309 answered · Aug 07, 2023 at 10:13 AM

The features you're describing of what you want is just ESS as far as I'm aware, I thought Hub etc were just old names for the ESS modes.

I'd maybe suggest setting up software side from scratch again as it definitely sounds like a setting is not quite right somwhere.

In terms of PV not starting when AC coupled to me that sounds like a frequency shifting issue. When you add ESS assistant in VeConfig it asks you if you've got AC coupled PV and guessing you'll have pressed yes and then it asks you to enter frequency shifting information.

This allows the victron inverter to adjust the frequency of the power it's outputing say to 51hz as a way of communicating with the AC coupled PV. The AC coupled inverter will see an incorrect/unsupported frequency and disable output. Some AC coupled inverter have features where you input the same frequencies input in VeConfig and there'll be like a "reduce output" frequency and then a "off" frequency.

That's the first place I would check for the PV issue.

Frequency shifting is usually only activated when batteries are full so unusual that it's flagging at 30%, may be worth checking the battery monitor is being used in the settings as well.

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Answer 3 · 2023-08-13T07:26:59Z

ty-web answered · Aug 13, 2023 at 07:26 AM

cheers matt1309, i am away for a couple of weeks, will take a look when I get home.

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