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martin-henning avatar image
martin-henning asked

ESS minimum SOC top up with scheduled charging

Hi folks,

running a 3-phase 5kVA MP-II system here, AC-coupled PV on AC_out, running 4 batteries with internal BMS and relying on smartshunt for voltage/SOC here, hence no DVCC. Float ist set to 55,4V, absorption to 57V in the multis.

The scenario in this case is, that the grid is almost always there, so the purpose is maximisation of self-consumption.

Therefore a minimum SOC of just 20% has been set, which "unfortunately" is being undermined by a few DC loads connected to the battery - my first understanding of the min SOC was wrong here, I somehow expected a "keep charged at 20%" feature.

So to battle this I opted to charge n schedule once per day to reach the 20% again for emergency purposes. I do successfully enter the "scheduled charging" state, so I don't have the time problem many others seem to have. I just can't seen any rise in voltage or current. Where is my problem? :)

screenshot-2023-01-24-at-131941.png

Voltage keeps dropping...

screenshot-2023-01-24-at-132029.png

Any ideas? :)

Just in case the relevant settings:

screenshot-2023-01-24-at-141317.pngscreenshot-2023-01-24-at-141346.png

Thanx,

Martin

ESS
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1 Answer
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guy-cashmore answered ·

The SOC limit function has a hysteresis, I think it's 5% from memory, so the system won't begin to charge unless the batteries are below 15%, so the charging schedule only stops the consumption from batteries for the set period instead (this function can be useful elsewhere).

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martin-henning avatar image martin-henning commented ·
Hi guy, that sounds plausible but I could find this documented only as a function of the BatteryLife feature, which I am not using. I will let it drop to check whether this also applies without BatteryLife.


Though it seems this would not touch my scheduled charging problem - no matter what other functions would eventually begin to recharge, I would have expected charging current/voltage when the Multi has successfully entered the Scheduled Charging state... That's where I am wondering about the non-effect of that system state.


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martin-henning avatar image martin-henning martin-henning commented ·
To add to this: As opposed to what I understood from the manual, the hysteresis seem to be there present even without Battery Life. So dropping down to 15% will indeed start charging. Now whether scheduled charging is also affected by some sort of internal theshold or not, I will have to find out. At least it seems I cannot enforce earlier charging through that function - it simply does nothing for me.
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guy-cashmore avatar image guy-cashmore martin-henning commented ·
If stop on SoC is active, scheduled charging won't commence unless the battery state is 5% below the SoC stop setting.
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