I live in the polar vortex and so walking outside I’ve had a full phone battery go dead in under twenty minutes. We’re talking idk ≈ -40F. When it’s warmed up again there it is suddenly at 60%. I don’t expect to understand well because I know little about batteries, but what’s the deal? And how is it that once it’s warmed it is not only fully functional but has retained charge? At what temperature does this effect begin to take hold?