Question About Nighttime Inverter Battery Usage on FoxESS System

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Mi5iek
Posts: 1
Joined: Fri Dec 13, 2024 4:19 pm

Hello everyone,

I have a PV installation with a FoxESS H3–12.0–E inverter and a FoxESS Energy Cube ECS2900-H4 battery. At night, when the PV system isn’t generating power, or when the panels are covered with snow, it seems that the inverter powers itself from the battery.

The FOXESS CLOUD app shows that at night, the inverter continuously draws 15–16 W from the battery. I have the minimum SoC set to 10%, and the inverter correctly doesn’t drop below this level, except for maintaining its own operation. However, during two days without sunlight, the inverter powering itself from the battery has caused the SoC to drop to 5–6%.

Is this normal behavior for the system?

I would appreciate any insights or suggestions!

Thank you in advance.
Dave Foster
Posts: 1557
Joined: Thu Oct 13, 2022 7:21 pm

Hi, yes that is perfectly normal behaviour - the inverter never takes power from the grid unless it is charging the batteries.

If the batteries reach minsoc whilst there is no solar, the batteries will continue with the small drain to run the inverter/BMS and when the batteries drop below minsoc the BMS will request a low power 'top up' from the inverter. It is only on for a few minutes and will repeat every hour or so just enough time to charge the battery back up above minsoc.
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