Growatt SPF 5000 ES – Grid/Input Voltage Sensing – Fault 08

Recently, I’ve noticed a trend that my Growatt SPF 5000 ES is misreading the AC input from the grid. I know for a fact the voltage is normally around 240V on my grid supply, but in moist humid conditions 90% + RH, the voltage as measured by the inverter drops like a stone.

If the inverter is charging when the voltage drops, it will shutdown and go into fault condition, even stopping bypass from AC Input to Output, if it drops below about 160V measured.

I added a rule in my Solar Assistant setup that if the AC voltage drops lower than 180V to configure the inverter to “Solar only” charging and output “Utility First”, which stops it from charging the battery on cheap rate power.

Unfortunately, after 3 horrible days, dark and wet with little or no solar, the batteries gave out and I have no way to charge them.

One thing I can’t get my head around is that the output is also being misread, but only when in bypass mode. When in bypass mode the inverter reports the misread grid voltage, but while in inverter mode the output reading is reported correctly at ~230V

Output voltage as per inverter:

Voltage at fridge:

During the day the inverter outputs a pretty stable 230V, between about 02:00 through 09:00 the grid connects and is 240V nominal. The inverter seems to be flicking between bypass and inverting and totally draining the batteries as I power certain high loads only at night (I run dehumidifier, tumble drier, etc).

As per advise here – https://www.amosplanet.org/how-to-solve-spf-5000es-10-warning-output-power-derating/ I have also set Option 3 to GEN which lowers the acceptable voltage, but the input sensing is getting worse as time goes by. Some nights the inverter is not seeing any voltage at all and won’t even allow by-pass.

Charging the battery while the inverter “thinks” the grid is under-voltage seems to drive the bus voltage over the preset limits and results in a Fault Error code 04