The kind of batteries that we're talking about simply do not operate outside of the 0-35 degree Celsius temperature range. It will never be "ICE to charge batteries" because the batteries will not cycle in those conditions. North of 16C is optimal. The limitation is the chemistry.
If you look at the temperature variance across the planet, you'll realize that there's vast numbers of people for whom batteries are never going to be an option.
If you look at the temperature variance across the planet, you'll realize that there's vast numbers of people for whom batteries are never going to be an option.