Multiplus shows wrong AC In voltage

DIY
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1

I have a system with two MultiPlus units connected in parallel on a single phase. Everything worked fine for 2 years, but a few days ago, during the night and under low load, one of the MultiPlus units started showing approximately 100V on AC In instead of 230V. The other MultiPlus still shows 230V and operates correctly. Both units are installed in a dry, clean, and well-ventilated room.

What I’ve tried so far:

  • Measured the AC input with a multimeter — it’s 230V on the cables.
  • Re-applied all settings using VEConfig.
  • Flashed the firmware to an older version (v443), then to v446, and finally to the latest (v556) using the Firmware Flasher.
  • Checked all cables, connectors, and terminals.

But nothing helps — it stubbornly keeps showing ~100V instead of 230V, and as a result, it doesn’t charge the batteries. However, it still works correctly as an inverter.

What else can I try to fix it?
Where to fix it in Poland ?

Napiecie 110V
Napiecie 110V797×632 53 KB

2

This indicates a fault - if the AC in Voltage on the terminals in the Multiplus is 230V, then the fault is internal to the Multiplus units. If you have the AC in paralleled, then the fault is common to both inverters.