FoxESS Community - Owners & Installers Forum

Last couple of days when the battery gets to 50% the Inverter starts charging it from grid,for the past 9 months since I've had the system it's not done this till battery gets to 10%
Can anyone help why this would happen all of a sudden?

Odds are very high that your 'Min Cell Temp' was so low that it charged from the grid to keep warm (was a post just yesterday, and last year on same subject) viewtopic.php?p=19548#p19548

You can look at the v2 website to get some details from your inverter for the overnight temperatures.
https://www.foxesscloud.com/v2/login

It was -4 last night,first frost of the year so might well be that,thanks.

Find out if you can the Min Cell Temp, then you will know the answer for sure, bonus points if you post a picture

Also, I do see that you have heating enabled in the App, if you can post your settings and battery type & firmware version, then these can be checked. For example, the EP battery IIRC needs version 1.009 to actually fire the heater, mine came with 1.004 and the App showed heater was 'On' but it never warmed up.

Looks like it's version 1.007 but not sure how to update the firmware

Nuts! Well this is installer/Fox to upgrade this.

email your inverter SN to service.uk@fox-ess.com, ask for battery FW upgrade to enable heater to function correctly.
There's a possibility that your inverter might need upgrade too so that it can support this, so maybe if it needs it, ask for this also, give them battery SN(s) also just in case.

Hi,yes I emailed them all the details earlier this morning including screenshots but not yet heard back, thanks again

It will be sorted Mon or Tue at the latest, not sure they do work over the weekend.
Did you manage to find out the overnight temperature of the battery from the v2 website?

Sorry no,not that clever

Spud wrote: ↑Sat Nov 14, 2026 1:51 pm Sorry no, not that clever

I believe in you, if you want to give it a go...


Login to the v2 website -> Devices (on the left side) -> Click on your Inverter and then you will see the filter choice in the above image.

You can only filter 2 items, so I would go with 'GridComsumption Power (kW)' & 'Min. Cell Temp. (°C)' so you can see it pulling grid energy when the temperature = x °C

Don't worry if you can't create a picture, but this helps anyone else following the thread.

Shows minimum battery temp at 8.1°
So would this indicate when battery gets to 50% it will start pulling from grid as it's at 3° here now and battery is at 75%?

If you can filter the values specified from the inverter, you can see when it started to do low temp charging, armed with this time, you can change a filter item to SoC, and when you locate the time it began to charge it will show you. It could be worth while checking out a few values in the filters to get an idea on things.

There is also some good information here https://fox-ess.tech/foxess-batteries-i ... batteries/
Despite saying this information is for non-heated in the link, this low temperature logic applies to heated also (AFAIK) from what has happened to you and others with cold batteries with heater element.

"Power Reserve Mode (PRM) activates when the minimum cell temperature is <3°C and the SOC is <60%, the system deploys protection measures (low-temperature power reserve mode), and the current limit value of discharge is temporarily reduced to 0, and the discharge is prohibited; when the SOC is >=65% or the minimum cell temperature increases to 5°C and above, the system exits the low-temperature power reserve mode, and the discharge is restored to normal. This is a protective mechanism for battery health and will clear when the temperature rises.

Please note, for EP5 and EP11 batteries, it is possible to alter the logic outlined above to reduce the SOC threshold deployed in PRM in certain instances. This would require special firmware which can be applied on a case by case basis."

Thanks once again for your help and advice,think I might just wait till Fox support get back to me with hopefully a firmware update as I don't really want to alter to much in values and settings

You won't be changing settings, just finding out what temperature charging kicked in, and then you can check the SoC that you wanted to know.

So in essence, you can answer your earlier question if you look up the data, especially now you know where to look.