In Canada, the CF is working on rebuilding their expertise in HF radio, as they realized that in case of large scale conflict, satellite systems aren't going to be dependable.
https://en.wikipedia.org/wiki/Canadian_Forces_Affiliate_Radi...
Yes, sorry, I was in a rush and didn't explain enough. For our usage, the cabin isn't occupied during the winter, and can drop below 0*C occasionally. The solar system is turned off though, so we don't worry about it.
If you're permanently there, it shouldn't be a concern. Sounds like modern BMS can disable charging at low temperatures so maybe not a worry for you at all if you're buying new batteries.