Inverter Self-Power consumption / efficiency

[half.price]

Hi all

Not sure, if this question has been posted already, but I do face a serious situation, making full setup questionable

I do have an H3 Foxx inverter, 6,5 kWp Solar and 8,5 kWh battery setup.

Inverter is described with 95% or more efficiency, but real data do show something very different.
Please check this examples:


Inverter does consume minimum 150 Watt and up to 300 Watt, depending situation

Ok over day with sunny weather. PV does give for example 4kWp, battery 100%, inverter output 3,8kWp. Loss of 200-300 Watt.
Strange at night. PV zero input, battery first discharging, house demanding (inverter outout) at 300 watt, but battery discharging with 500 Watt. So inverter using 200 Watt

And even stranger!!!!
At night, battery empty (at 10%), house usage 300 Watt BUT inverter still consuming 150 Watt!!! So grid consumption is at 450 Watt!!!

Why the hell??
This is far away from calling it 95% efficiency at all, as inverter itself does empty my battery over night

Is this as designed?

Any idea? Any input? Any setting I can take?
I would assume, inverter should go to Standby, using 5 watt, if battery is empty and PV does not bring anything.

[calum]

https://github.com/nathanmarlor/foxess_ ... ssions/419

Short version: yes, it's your inverter, no there isn't much you can do about it.

[m15k]

This is really annoying. It seems to depend also on the battery size. At night: 0 Solar, 10% SOC, my FoxEss draws 330W...

[alistair.miller]

I am not sure if this will help but it could be worth making sure your system is using the latest versions.

I found our system using around 90 watts but since getting an update a few months ago the usage is more like 27watts.

[m15k]

I am not sure if this will help but it could be worth making sure your system is using the latest versions.

I found our system using around 90 watts but since getting an update a few months ago the usage is more like 27watts.

Can you post your firmware versions? Can the firmware be updated manually?

I'm running on:

Master Version: 1.83
Slave Version: 1.02
Manager Version: 1.43

[alistair.miller]

Ours is a h1 inverter so I'm not sure versions will be of much help, versions being:

Master Version 1.63
Slave Version 1.02
Manager Version 1.68

But the updates have helped so it's possible any newer update may also improve your system.

There are a few on here with a vast amount of knowledge who can offer more advice than I could ever do.

Updates for us, we have to ask FoxESS support each time although the preference is your installer keeps you updated. I don't think there is a way for end users to do it.

[m15k]

I wonder what the inverter is doing with that amount of power. From my knowledge it started to draw that much power when the batteries were installed.

[alistair.miller]

When we started off with an 8kw battery system it always seemed our system used around 40watts extra an hour for a house load of 200 watts or less. When we took the battery size to 28kw this jumped to over 90 watts extra being used.

We downsized to 20kw and that number changed to around 50 watts. Since an update or two ago this now seems to be around 20 - 30 watts so for the h1 and cubes they seemed to have improved the system.

I remember a FoxESS tech support mentioning some of the usage / loss will be down to the inverter matching the battery valts to the mains valts. Although some of what was said went over my head.

We have a family member with the same set up but they have a 16kw battery which works out at 240 volts and they seem to use / loose much less than we do, with ours being around 300 volts and our mains being around 243 volts so I guess some of what he said must be true.

Temperature and the amount of power being converted from dc to ac changes the amount it uses of course which can result in a few 100 watts being lost when converting several kws.

We only use the fox app which isn't 100% correct in the data it shows so I take it as a guide only. It never matches our smart meter.

[calum]

The inverter has to keep the necessary power electronics ready to provide multiple kilowatts of AC power at a literal moments notice. Think about if you turn on the oven, or boil a kettle, or turn on a hairdryer, or possible several of these things at once. Doing that is not 'free', energetically speaking; there are some inefficiencies, and those inefficiencies are greatest, proportionally, at low loads.

Certainly the firmware that controls the power electronics can be made more efficient, and this is a good reason to keep up with firmware versions from Fox, there have been very noticeable efficiency gains vs the earliest firmware versions. But there are also limits to those improvements, as you approach the limits that the physical electronics are capable of.

As an aside, the Foxess app / website can never be very accurate, as it only samples what's going on every five minutes to give you an idea of what is going on with power flow between the various components. If you want more accurate readings and data, you need to connect to the modbus interface of the inverter with NodeRed, Home Assistant or whatever.

[tommyhechtel]

Hello.
I understand the inverter needs a certain energy consumption of 200W or more for AC/DC transformation and to be ready to provide instantly a high amount of energy from PV or battery.

What I do not understand is why the inverter also uses 200W with battery on min SOC and no PV input (at night).
I would think then the inverter goes to "cold standby" and just uses about 15W while the complete load is directly taken from grid without any need for AC/DC transformation or charge/discharge of battery.

In winter times with 16h without PV input and empty battery this means a difference of 3 kWh every night.

[calum]

Hello.
I understand the inverter needs a certain energy consumption of 200W or more for AC/DC transformation and to be ready to provide instantly a high amount of energy from PV or battery.

What I do not understand is why the inverter also uses 200W with battery on min SOC and no PV input (at night).
I would think then the inverter goes to "cold standby" and just uses about 15W while the complete load is directly taken from grid without any need for AC/DC transformation or charge/discharge of battery.

In winter times with 16h without PV input and empty battery this means a difference of 3 kWh every night.

The thing is, the system doesn't "know" where it is, or when the sun will come up, or any of that - it is engineered to be ready at all times, in case needed.

I imagine it would be possible to have a low power mode that would wake up the main power circuits when they are needed, to deal with the circumstances you describe - particularly if the system had a way to know when to expect sunrise and sunset. Presumably the cost increase, in both hardware and engineering, is prohibitive in a very competitive and price-sensitive market.

Unfortunately this is the hidden price for home solar and batteries - they are always using a bit of power in the background.

[tommyhechtel]

I am not a specialist on electronics or software at all, but is this really so much impacting the hardware solution?
Couldn't this be solved by software logic, maybe similar to

In case Battery state at min SOC and:
1. PV input < x V for > 10 min => System standby (inverter inactive, no interaction with battery, "cold" standby consumption)
2. PV input > x V for > 10 s => System wakeup (inverter active, interaction with battery, "warm" standby consumption)

Instead of PV voltage level also the sunrise and sunset time based on location could be used in combination with SOC to determine cold standby phases. Or just let the user input those information in the app.

Don't get me wrong, probably this is not possible for certain reasons. If it would be so easy for sure it would be implemented already from the beginning.
I just try to get a better understanding of the "standby" power consumption when all loads are 100% covered by grid.

In my case it looks like the battery is constantly charged and discharged 1-2% over min SOC at night since firmware update (1.69/1.03/1.87).
So "expensive" grid energy is used to charge battery just to push most of it back to grid then for almost no money. And this of course + 200 W inverter consumption.
For sure not a very big commercial impact, but not really following my expectations about the high efficiency that is promised for FOX ESS inverters.

Ticket is raised and closed already with the feedback that next update should improve the situation. Fingers crossed

[v1lad]

HI All !
I faced the same situation after this morning's update. My inverter is now consistently drawing 150W from the grid at night with the battery at minimum ( 10% ).
Update was from 1.56 to 1.71.

I have found solution: Factory Reset, after you need just set up safety standard / country code and date / time.
The consumption dropped from 150W to 7W.

P.S. I got happy too early. In the morning, the problem returned. The inverter started consuming 150W again.

P.P.S Support made downgrade for me
Master : 1.69
Slave: 1.03
Management : 1.71
And seems the reason was downgrade Master from 1.90 to 1.69.

after the downgrade, the inverter consumption dropped from 150W to 40W in active mode.