question

bergmans-trading-cc avatar image
bergmans-trading-cc asked

ESS Batteries discharging in "keep batteries charged"

Good evening

I have a question regarding ESS setup with mode set to keep batteries charged.


System background :

Victron quattro 15kva

14kw PV array

3 x 250/85 TR

Small battery bank 48V 225Ah AGM(for now)

Inverter as battery monitor.


The issue I am facing is that battery power is used even though grid is available during night time. The system is set up to keep batteries charged with SOC of 100%.


The goal is to only use battery power if the grid fails due to load shedding or grid fault.


However when AC load peaks at about 12k watts, AC input voltage drops visibly on the graph. Battery power is then used to supplement demand.


This is unwanted. AC low disconnect is set to 210V and reconnect 220V.

Could it be that the voltage dropped below AC low and the system logging resolution just doesnt show?


Please advise

MultiPlus Quattro Inverter ChargerESS
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3 Answers
Murray van Graan avatar image
Murray van Graan answered ·

Hi @Bergmans Trading cc. It’s probably exceeding the ac input current limit, when this happens the system uses battery power to try and adhere to the set ac input current limit. Look at increasing the ac input current limit - provided your cables and breakers can support the higher current. I must say the battery bank is awfully small for the inverter size, Pv array size and loads you’re describing.

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bergmans-trading-cc avatar image bergmans-trading-cc commented ·

Thank you. I do realize the battery bank is too small. The idea was to manually decrease the AC load before scheduled load shedding. The addition of an essential DB for this scenario would be a better option as grid failure can occur when it is not possible to reduce AC loads manually. However I do believe more batteries are needed to accommodate for multiple grid failures within a day.

Any other suggestions to optimize?

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Murray van Graan avatar image Murray van Graan bergmans-trading-cc commented ·

Definitely, splitting your loads will help. In the end, lifepo4 would be the way to go when you upgrade the battery bank. The size would be determined by your critical load, and how long you want to power these items

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bergmans-trading-cc avatar image bergmans-trading-cc Murray van Graan commented ·

Have the lifepo4 really proven themselves yet? Just hesitant about the warranties? Has there been any history regarding warranty claims? What are your thoughts on the older tech 2V 1000Ah batteries?

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Warwick Bruce Chapman avatar image
Warwick Bruce Chapman answered ·

What is the input current limit? If it is too low, PowerAssist will use batteries to support loads.

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bergmans-trading-cc avatar image bergmans-trading-cc commented ·

Also power assist is unticked in VE Config

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bergmans-trading-cc avatar image
bergmans-trading-cc answered ·

Input current limit was set to 63A to match the rating of the breaker that feeds to the inverter.

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman commented ·

And what is the rated Amperage of the feed from the utility. Are you sure it is greater than 60A?

Can you share the graphs with us?

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bergmans-trading-cc avatar image bergmans-trading-cc Warwick Bruce Chapman commented ·

Attached are a few graphs of utility peaking.

The other symptom I see is that when alot of power is drawn from utility the voltage drops from 235V to below 220V. The resolution of the data does not show it dipping below 210V but I suspect that it does and then utility is uncoupled by tye inverter. AC low disconnect was set so 210V and reconnect 220V. This however seems to be causing problems as dipping in voltage can occur during night time when no PV is available. I have not seen the utility consumption reach >63A. And as I say power assist is not selected.


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Warwick Bruce Chapman avatar image Warwick Bruce Chapman bergmans-trading-cc commented ·

Please change AC low disconnect to 180 and let us know

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