I apologise if this topic has been covered before but I could only find the standard advice of keeping batteries warm and swapping them out which is what I normally do in winter conditions.
However, next March I am on an extended trip into Northern Norway, about 300km North of the Arctic Circle. Temperatures could easily drop to -40° (Centigrade or Farenheit, this is the point that they are the same.)
We will be snow shoeing, bivouacking and using snow holes for sleeping. Battery charging facilities will simply not be an option and practically there is a limit to the number of batteries that I can permanently carry under my jacket.
Obviously the batteries perform better when they are warm but what I do not know is whether they actually lose charge when chilled or can I store some in my unheated sled/pulk and just bring a few up to heat each day, under my clothing, before swapping them over?
If anyone has had experience of this kind of situation I would greatly appreciate some advice.