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nickdb asked

ESS and SOC

I am quite new to ESS.

I set a schedule to run off batteries overnight with a schedule limit of 80% and a minimum SOC of 75%.

At the beginning of the charge schedule the SOC was 79.4% and the inverter had changed its state to BULK for an hour before but obviously wasn't going to grid.

two questions:

1)I would have expected the system to go to grid to top up to 80% when the schedule started, it didn't (I may be misunderstanding the mechanism).

2)Refer to below image. Batteries started gradually charging from solar as excess power became available. You can see the gradual curve. Rather suddenly the SOC jumps from 84% to 100% yet nothing has been pulled from grid and there isn't sufficient solar yield to have caused this. Is this a glitch?


Multiplus-IIMPPT ControllersESS
screenshot-2020-07-28-at-100125.png (55.4 KiB)
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Alexandra avatar image Alexandra ♦ commented ·

@nickdb

I experienced something similar to this when a lithium bank bms had a wobble.

It may be something to do with your battery settings though as I see you are using the inverter for SOC. Or if it is a new system the SOC has not synced correctly yet.

Did the inverter go into pass through at least?

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nickdb avatar image nickdb ♦♦ Alexandra ♦ commented ·

I have a smartshunt (BMS) that is determining SOC. Battery settings are unchanged, the only variable is that ESS is now enabled. System has run a while and had several discharge cycles.


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2 Answers
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nickdb answered ·

Sounds like my shunt (using defaults) wasn't optimally configured.

Have adjusted the charge voltage to be near float voltage, reduced tail current and increased the detection time. Will see how it runs tomorrow when hopefully there is a bit more sun than today.

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nickdb avatar image nickdb ♦♦ commented ·

I see the manual states 0-2-0.3V below float voltage.

In a training course (but not in the manual) it says that solar installs should be 0.3V below absorption voltage..

So which is it? >:!

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Alexandra avatar image Alexandra ♦ nickdb ♦♦ commented ·

I have mine set to 0.3v below using lithiums. Not all the systems I have installed are the same so you may need to adjust again especially if you get soc drift over time.

Also check which device your GX device is using as SOC reference.

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nickdb answered ·

Much better today with the changes. I set charge voltage to halfway between float and absorption.

It didn't quite get to 100% (99.7%) but we did run out of daylight.



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