FoxESS Community - Owners & Installers Forum

Hi.

I noticed last night that my battery was only charging at around 1kw per hour. Usually it’s the full 5kw per hour.

Now I see that my solar is producing 4kw but only charging my battery again at 1KW with the rest going to load plus export.

My charge current is set at 40A

Can anyone help please.

Thanks
Tash

This sounds as though it would be related to battery temp and de-rating.

Below 15 degrees I believe is where the battery will limit charge and discharge rates to protect battery from increased degradation/damage that can be caused from operating at full power while below nominal temp range.

I believe both web and mobile versions of Fox cloud show different figures for battery temp so they are not reliable, but the main thing to note here is that the de-rating is based on the lowest cell temp out of all the batteries. This is something that can only be seen when downloading all of the raw data as it lists both lowest cell temp and highest cell temp. If i am not mistaken, it will also show you the current battery max charge and discharge rates too which change dependent on cell temps.

Ah ok. Thanks.

My kit is in the attic so I should try to make it warmer but then it will be too hot in the summer.

I didn’t see the battery go below 18 degrees but I suppose there are tolerances.

I presume then that the home assistant modbus data fo the battery is the two items below that I should look at ?

Yes, it triggers off cell temp low - that’s the one to watch. A bit of kingspan insulation board around the batteries makes the world of difference (quite a few posts on here about that).

Thanks Both.

I took your advice and built an enclosure using kings span and whilst the attic has stayed at around 6 degrees, the battery temp has recovered and was able to charge at full rate.

I’ll remove it during the summer.

Thanks again.