Photovoltaic system offer for our single-family house

The basement is ideal for the battery, if only because of the year-round temperatures there. Mine is there too. I wouldn't want it in the garage; it can get very cold there in winter.

BYD specifies -10 degrees as the minimum temperature the storage system can withstand … we will insulate it further

BYD states -10 degrees as the temperature the storage can withstand …

right, "withstand". If it gets colder, you either take it down or hope for the effect of insulation? Incidentally, BYD's statement only applies with the footnote "from -10°C to +5°C the performance is limited" - whatever that means in detail.

So I don't think my garage will drop significantly below 0 degrees … even in the garden shed without heating in winter the olive tree survives

If necessary, install frost guards. Although I do not know to what extent d is considered a fireplace.

Exactly in Swabian, just google "Explosion hazard: energy storage from photovoltaic systems as a ticking time bomb in single-family homes” :)

If necessary, install frost guards. Although I don't know to what extent d counts as a heating appliance.

Heating appliances are defined for us as oil, gas, pellet (or firewood etc.) Heat pumps or frost guards (electric) are not considered heating appliances.