FoxESS Community - Owners & Installers Forum

Hi all, had my solar+battery system installed last month with a KH7 single-phase inverter and a couple of EP11 batteries, so I'm new here!

I've got my Home Assistant box all connected with the inverter and set up an energy dashboard, but after a couple of days I noticed some odd data being reported, and it appears to be caused by the Battery Discharge Today sensor data.

I have set up overnight charging from 12:30am to 5:30am via the mode scheduler, charging the batteries to 70%. This normally takes less than an hour, and remaining on charge mode for the remainder of the low-cost energy period. This results in the overnight house load drawing from the grid, leaving the battery untouched.

I would expect the 'Battery Discharge' data to show no change during this period, since the battery is initially being charged, and then left unused. It does show no change during the charging period, but then shows around 300w of load during the period it sits idle at 70% whilst the house is drawing from the grid.

This is shown on the attached chart - the yellow shaded period is during the 'force charge' work mode.

After the low-rate period ends, and the house starts drawing from the grid, the discharge rate rises for the load, but appears to maintain this 300w additional load throughout the rest of the day, meaning by the end of the, total consumption on the dashboard shows much higher than the actual consumption by around 7kwh. This is backed up by

Has anybody else noticed this with their KH7 inverter? If so, did you find a way to fix the data?

I've tried creating a custom sensor from adding and subtracting various other data points that are working, but haven't got it perfectly right. I'm thinking about creating a custom sensor which just deducts 300w from the reported battery discharge data

The inverter and batteries take power to run and there are numerous losses in the system, chemical losses in the batteries, power to run the BMS, the inverter DC to AC in the solar MPPT’s, and AC to DC in recovering power from PV or the batteries.

300 watts appears to be high, normally i’d expect 100-150 watts in my experience the battery discharge sensor is not that reliable as some of the losses get added to the load and the losses increase with discharge power which can mess up the statistics.

I’ve done a few things in my home assistant to compensate with a ‘real battery discharge’ sensor that takes into account the losses which increase with load but in all honesty the main metric I focus on is the parasitical grid usage per day - this can be reduced by setting a ‘grid compensation’ (installer only setting)

Hi Dave,

Thanks for your response; you're right, there is a minor change in battery charge state equivalent to around 100 watts, losing nearly 2% of charge from the point it reaches the desired 70% level and the end of the force charge period. That's equivalent ot around 400 watts over four hours, which must be the system-usage coming out of the DC circuit. Now that I think about it, the draw from the grid during that time is consistent with normal house load, and would be higher if it were running the system.

That nearly 2% drop in battery charge is not consistent with the battery discharge sensor data showing 1.3kw was drawn from the battery during those same four hours. Either the sensor data is wrong, or it's including the house load in this during that time period.

How exactly did your compensation workd for your real battery discharge sensor? Assume you coded a template? Would you please be able to share your code?