My tip in the flat, reason winter half-year.
I have tried to insulate the battery together with the WR.... over night everything cools down and then the battery no longer charges until it has 5 degrees plus again because of its own protection.
There are flat cables from Ecoflow here on Digitec that you can clamp in the window. Then the battery and inverter in the flat.
Per panel you need 1 such cable is always plus and minus together
EcoFlow MC4 cable