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Nico Bayer avatar image
Nico Bayer asked

ESS Low SOC Battery not idle / charging from grid

Hi,

ich noticed something with my ESS system last night. When the low SOC limit (5%) is reached, the battery does not go to idle and the loads are supplied by the grid, but the multis charge the batterys back up 2% then the loads are supplied by the battery againe. This behaviour repeated itself during the night.


This is not normal mith my system. I have never seen this before. The system behaves normal when the low SOC limit is 10%
I updated the system last week. Multi FW v481 -> 490, MPPT v3.02 -> v3.08, GX -> v2.73
All the setting stayed the same.

This is befor the update:

soc2.pngSystem:

ESS 3-Phase

3x Multiplus II 5000
8x Pylontech US3000C
2x MPPT 250/100
1x Fronius Symon 15kw
Cerbo GX

ESS
soc2.png (77.4 KiB)
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4 Answers
nickdb avatar image
nickdb answered ·

What is the inverter cutoff settings?

What are the ESS assistant and ESS (in the GX) settings?

A bit more info is needed.

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Nico Bayer avatar image Nico Bayer commented ·

Hi,

the settings:
cut-of-settings.jpgess-assistant.jpg

ess-gx.jpg

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ess-assistant.jpg (163.0 KiB)
ess-gx.jpg (63.2 KiB)
nickdb avatar image
nickdb answered ·

You have have a negative 30W setpoint so the system will keep trying to push back 30W. That has to come from somewhere.

Try raise it to a low positive number.

Tho thats tiny for the size of the pack, so it’s probably a larger setup issue.

You have no inverter soc cutoff and 5% is low for ess minimum.

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Nico Bayer avatar image Nico Bayer commented ·

Hi,

the negative setpoint prevents the system from pulling energy from the grid, when there is no need for it. This is set up like this for months and works fine. When the low SOC limit is reached the Multis switch to passthrough and the loads are supplied by the grid.
Now the Multis immediately start charging the battery when the low SOC limit is reached.

I think it maybe has somithing to do with the battery voltage beeing to low for the reported SOC so the Multis start charging.

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nickdb avatar image nickdb ♦♦ Nico Bayer commented ·

At 47.9V you're above the ESS and inverter cutoffs.

This seems to be triggering the ESS minimum behaviour.

What does the remote console dashboard report for ESS status - #1 etc?

Perhaps the current code does not like the ESS minimum being beneath 10%.

screenshot-2021-11-22-at-120749.png

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Nico Bayer avatar image Nico Bayer nickdb ♦♦ commented ·
It shows #1 when the low SOC is reached and the battery is idle. I dont know what it shows when it recharges the battery.
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Nico Bayer avatar image
Nico Bayer answered ·

Last night i had set the low SOC limit to 10%. It reached 10% during the night and the battery went to idle and stayed there. The loads (ca 500w) were supplied by the grid. This is as it should be.

In the morning (battery still at 10%) a load started pulling 2kw from the grid for some time. In that moment the battery started slowly charging from the grid againe until it reached 11%.

4.png


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nickdb avatar image nickdb ♦♦ commented ·
#1 is what you would expect when the system hits the minimum ESS SOC, ESS should then prevent further discharge and draw loads from grid. Once PV returns, this will be used to charge until a few percent above minimum SOC before serving loads again.

It looks like ESS is only happy with a minimum SOC of no less than 10%, setting it to 5% might be breaking its algorithm.

I have never set ESS that low before as it is extremely rare to have cutoff disabled on the inverter.

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hominidae answered ·

I have the same issue, independant of the lower Soc being 10% or even 40% (now with battery life).

The grid setpoint is set to 0W.

When the lower limit is reached, discharge stops and a small amount of energy gets fed into the batteries, until SoC is 1% higher than the lower threshold. After that, charging stops and the SOC somehow settles in at the lower threshold again.

I have a set of 6x US3000C from pylontech..only a couple of weeks old and no alarms seen so far.

They are doing fine. However, my DSO explicitly states, that charging from the grid is not allowed (under all circumstances). The EM24 as grid meter along with the ESS algorithm in the Cerbo should take care of that, shouldn't it? I am worried, that at some point, someone will look at the meter readings from the DSO supplied meter (which should stay at zero kwh, but now isn't anymore).

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