Originally Posted by
rumrunn6
auto batteries aside. I wonder if a bike light battery, best practice, would be to let a very cold battery warm up inside a little while before plugging it in
Probably a good idea, since the charger may be designed to operate at its best within a certain temperature range. If it's a lithium battery, it may have a built-in temperature sensor (typically a third terminal) that the charger uses to help control the charging process and prevent thermal runaway.
I wonder if it makes sense to just have two batteries, and use them on alternate days.