Technical Support

As background, I had my 8kW Sunsynk inverter destroyed (by lightning, most likely), and Sunsynk replaced the mother board free of charge - thank you Sunsynk.

Now, the issue: In December 2023 I had the inverter's timer set to use grid/gen only when the NMC battery's BMS reports 11% SOC or below.

However, I noticed that the inverter will use grid when SOC still at 22% in that 04:00-09:00 timeslot.

This behaviour was only seen when the SOC below about 23%. Once the battery charge was above that SOC, inverter behaviour was correct.

After a chat with my installer, and checking every single inverter setting that could have an influence, we agreed that a factory reset on the inverter is the only option. Did that. [I also do monitoring to Home Assistant via RS485, and the factory reset caused all incrementing counters coming from the inverter (kWh, etc.) to start afresh - bummer, but no train smash if this solves the issue.] I checked and the next day or two, and there was no grid charge when it should not, so I figured the counter loss was worth it, as the inverter is now behaving correctly. However, come January 2, and I noticed the same use-grid-when-it-should-not behaviour again. Minimum SOC is set for 12%, but grid charge is already used when battery discharging but still at 16% SOC. It's a bit different from the 22% where it started before, but still an error.

Firmware bug? Running version M 6.0.2.4 / S  1.7.2.4 / C E.4.2.4

Or how can I fix this?

For the commenters on my 11% SOC setting: My 4 x Hubble NMC batteries (not LiFePO4) are 5.5 kWh (110 Ah) each, but Hubble have us set the charge voltage (53.6V) and battery empty voltage (44V), and of course, the BMS, so that we only operate in the "easy" part of the NMC charge/discharge curve. So taking the battery down to 10% SOC is actually only taking it down to about 24% of 5.5 kWh, as measured by my Victron shunt on the battery line.

My apologies: I only saw after I posted that the issue was already reported, but not really solved, in https://www.sunsynk.org/forum/technical-support/5kw-inverter-10kwh-battery-ignoring-settings-charging-from-grid-when-below-24 But perhaps this means my m/board needs replacement again?