FoxESS Community - Owners & Installers Forum

Hi all,

Amongst the many cycles governing our world the Stupid Question cycle is, for me, the most prominent.

Today's example:

I have had the Battery warmup function enabled by Fox and so I can now see in the app (under quick settings - see attached image) a line which when clicked upon takes me to the next page (next image) which seems to say to me that I enabled the warmup starting at 4 degrees C and ending at 12 degrees C with the time period set from 00:00 to 08:00 enabled (why does Fox think it's low price - it really depends on the tariff doesn't it?).

I have set other limits - like 8 degrees lower limit - but it doesn't seem to work, in that I would expect to see a gradual warmup occur?

As ever, very grateful for replies showing how I'm not really understanding how this works and indications as to what is really going on.

Postscript - the other thing is that this ability to enable/disable only appears in the app and not in the web version.

Best regards,

Derrick.

Here is a video you can look at to show the system when it is working, you will see a clear animation.
viewtopic.php?p=10871#p10871

Fox won't know what is your cheap tariff, but you set this yourself if you have off peak(s) period(s) once or more times per day. If you don't have offpeak, or wish to have it heat at any time in the 24hr, then you adjust accordingly (00:00 to 23:59)

The heater function will only work if you have a minimum firmware version, so you can find this in your App by going to devices, battery and clicking on the serial number.

And yes for now the heater function has not been added to the website version, it would be nice if there was there for full functions.

Hi MB,

Very curious - the version of my BMS firmware is (see attached) 1.011 and this is the message I received from service.uk@myfoxess.zohodes.eu: "Hello,

The low temperature has restricted the battery behavior, and I have upgraded the system to the latest version and turn on the warm up function for you.

Best regards,
Dovis"

So I'm puzzled as to why it won't come out of Standby. It certainly doesn't animate as shown in your very helpful video.

My wife calls this situation as "The Steed Effect".

Best regards,

Derrick.

You would need to set your start temperature above the current value, so if the temperature is 7.7°C, you have to move your top slider to say 9°C.

Next you need to have some PV generation, say about a kW should do it, or you need to adjust your off peak grid time to 24hrs. This will at least test that it is working.

I don't think you will need to restart your whole system, but then again this is Fox, and bugs are free and plentiful.

Hi MB,

Well, I did as you recommended and something curious occurred last (post midnight morning actually) - during a period from 01:59 to 02:25 the grid provided and the battery drew just over .5kW and at 5:44 (Cat checking I'm not dead) I checked with the app and the battery temp was 12.5 degrees C. When I arose later, around 07:15 it had fallen to 9.1 degrees C.

And when I checked with the desktop dashboard at 09:31 it showed that the battery was in warmup mode and the temp was 12 degrees C. And when I checked the app I could see the animation similar to the videa you supplied. So, it seems to be working but I'm confused - last night's warmup occurred during the period I set 23:00 to 07:00, but why is it warming up outside that period? I suspect that it's Fox's weird working of time periods in that it reads what I've set as all day because it can't cross the midnight line.

All in all, it seems to be working - in a weird way.

Best regards,

Derrick.

MaterialBarracuda48 wrote: ↑Mon Feb 16, 2026 2:08 pm Next you need to have some PV generation, say about a kW should do it, or you need to adjust your off peak grid time to 24hrs. This will at least test that it is working.

Sysiphus wrote: ↑Tue Feb 17, 2026 9:56 am SNIP SNIP

last night's warmup occurred during the period I set 23:00 to 07:00, but why is it warming up outside that period? I suspect that it's Fox's weird working of time periods in that it reads what I've set as all day because it can't cross the midnight line.

Morning Derrick,

I gave a clue in an above post I quoted.
There are supposed to be 3 ways to heat the battery up.
1. Grid charging, as you have set now
2. PV generation, so if you make I think around 1kW of power, then it can use this to heat
3. Self-use, if SoC is above 40% (IIRC) then it is supposed to be able to use it's own power to heat

I have never see the 3rd way work, but then my battery has not heated in ages. I have seen 1&2 working just fine myself.

Glad that you got some action out of the heater, and animation to verify.


EDIT: In 2. PV generation; the 1kW of solar to heat, might actually be lower, but it does need some PV available to wake up the heater function