Inverter in Sustain mode and low battery voltage

DIY
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Hi Victron Community,

We are facing an issue with our Victron ESS setup, where the inverter remains in sustain mode, and we are getting a low battery voltage alarm, even though the battery voltage appears to be normal.

System Details:

Victron Ekrano GX
Multiplus II 48/5000/70-483x Pylontech US5000 batteries
BlueSolar MPPT VE.Can 250/100
Fronius Primo 3.6-1 (grid-tied inverter)
ESS Assistant enabled

Problems We Are Facing:

  1. Low Battery Voltage Alarm
    The system shows a low battery voltage warning despite the actual voltage being within an acceptable range.
    The battery readings seem fine, yet the alarm persists.
  2. Inverter Stuck in Sustain Mode
    The MultiPlus II remains in “Sustain” mode, instead of supplying loads properly.
    We suspect this might be linked to DVCC settings or an issue with the Pylontech BMS communication. And due to sustain mode the batteries aren’t discharging at all. I have attached screenshots of the dashboard and key system settings to help diagnose the issue.

Has anyone else experienced similar problems with Pylontech US5000 batteries in an ESS setup? Any suggestions on what could be causing these alarms and why the inverter is staying in sustain mode?

Looking forward to any guidance to help resolve this!

Thanks in advance.

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Pls post data from advanced tab

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Any specific one? Or an excel combining all?

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GlebeFarm_log_20250321-0000_to_20250321-2359.csv (273.0 KB)

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In your previous post you had a lot of screenshots, but the last tab “advanced” is missing.

Here you set the sustain voltage, its probably too low.

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Here’s it

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Your inverter has no sustain mode…

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???

@IanE Show us a screenshot of the VRM dashboard and the configuration of the ESS assistent (click on summary).

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The batteries are not just discharging.

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Your sustain voltage is much too low, set it slightly under the mppt flloat voltage.

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Will that help in discharging? As of now it’s showing external control and not in sustain. Also if the battery temp. is 8 degree can this be the reason for not discharging? As Pylontech limits it with temp.

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Sorry, i was still locked to your initial problem.

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Yeah but after all that the batteries are just not discharging.

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I solved the charging problem for you, sorry that i can’t help with the discharging one.

This is probably? ESS, i have no contact and experience with this product, please ask the victron guy’s for help.

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Is it possible the temperature of the battery bank is the problem? I see 8 there.

Do you have these or a battery that uses the protocols?

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Yes, these are the ones. I also have a question regarding the temperature

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The charger settings are quite high for Pylontec, which was why I i asked. It is way out of pylons specified range.
Usually that is set to 51 and 52v in the charger tab.

Do you have optimised with or without battery life on as well?