Foxess Modbus and FoxCloud Different Temps

Dazlindazza · October 15, 2024, 10:58pm

I’ve recently installed a modbus to my FoxESS H1 inverter, which was much easier than I thought and as far as I could tell, receiving all the correct data.

The other day I had an email from the installer reminding me that as the weather gets colder the EP battery charge rate slows and stops completely at 0° stops completely. Their suggestion was to keep an eye on the battery temp and if the weather is going to be cold set it to charge from grid for a period overnight.

So… my plan is to set up some automations so that when the battery temp gets low to charge from grid until the temp increases again to save me having to worry about keeping an eye on it. This is when I noticed that the battery temp via modbus seemed higher than expected considering the weather is quite chilly, so i had a look at the Foxcloud app which shows completely different values. As I write this, the modbus data says battery is 26.4° where as the Foxcloud app is saying 15.1°

Comparing the other temp values, I noticed they seemed to be different too. I’m well aware the cloud data is delayed where as modbus real time but that still doesn’t explain the big difference.

Has anyone experienced something similar or got any suggestions?

Thanks in advance

roysilva · December 2, 2024, 11:45am

Hi Darryl,
I too notice this. Mine is just cloud integration and it reports 10c higher than what the app reports.
By the way could you please let me know how you did the Modbus integration and what hardware you used.
Many thanks in advance.

williamjeccles · December 8, 2024, 8:54am

Fox cloud uses the bms temp as the “battery temp” and the bms internals are often much warmer than the battery.

The Fox V2 mobile app reports the coldest cell as will the modbus integration.

Dazlindazza · January 10, 2025, 8:11pm

Hi Roy,
So sorry for the mega delay - I didn’t receive any emails to say I had replies so assumed no one had and this is the first time I’ve logged in since only to discover I did indeed have replies!

Anyway, I did quite a bit of research before getting the modbus and in the end went for this module: Hyuduo Rs485 To Wifi Serial Server, Rj45 Interface, External Antenna, Support For Modbustcp,Module: Amazon.co.uk: Computers & Accessories.

I then just followed the very detailed instructions from Github here: Elfin EW11 · nathanmarlor/foxess_modbus Wiki · GitHub.

I was somewhat daunted about it all so asked a load of questions to the great community on here who put my mind at rest so ordered the module. I did as suggested in the above link and used a USB cable to power the unit - it was just one of the many iphone charge cables I have, I cut off the lightning adaptor end that plugs in to the phone, stripped it back exposing 4 wires. The colours of mine were different to those shown in the link but a quick google gave me the info on which was + & - which I just connected as per the Github guide.

I powered off and isolated my inverter / battery etc and connected the signal wires as shown here: Modbus Wiring Guide · nathanmarlor/foxess_modbus Wiki · GitHub.

I think in the guide, Nathan used a length of USB cable as the signal wires between the inverter and the modbus, but the cores in the USB I used were really thin and worried they might break so just used a length of speaker cable I had in the garage which worked perfectly and certainly more robust.

I then setup the modbus device as show in the above guides before finally adding the foxess modbus integration to Home assistant. It asks for the IP of the modbus device and thats it, all the sensors etc are then added.

I realise after reading my reply, you might feel a bit daunted but honestly from no modbus to it being installed with all the sensors shown in home assistant took me 15 mins. I already had a display in my front room showing my CCTV so created a custom dashboard integrating my solar and CCTV in to one dashboard. Will try to upload a photo. Will also try to upload all the sensors the modbus allows access to, which of course allows endless opportunities for settng up automations which is why I mainly wanted it.

I expect after such a delay you probably worked out by now how to set it up on your own but thought the least I can do is respond anyway