From Dewalt.com
The temperature ranges we recommend for our Nickel Cadmium and Lithium Ion batteries are as follows:
Optimal Charging Range: 0C to 40C (32F to 105F)
Optimal Usage Range: -10C to 45C (15F to 115F)
Optimal Long Term Storage (on the shelf): 10C to 30C (50F to 85F)
Outside of these ranges, no damage is done; however, performance might be impacted as the chemical reactions slow down in extreme high and low temperatures.
At -20C (-4F) inside the battery, our chargers will suspend charging to protect the batteries. Between 0C and -20C, the charger will look at a variety of battery diagnosis factors plus temperature to determine whether to charge. In all cases, as soon as the battery heats up slightly, charging resumes.
We would recommend, when using the battery in cold climates put the battery on charge first thing or do a couple quick applications to get it warmed up. Best practice, whenever possible, try not to store them overnight in vehicles when the temperature really drops.
Yes, this is their optimal temperature range, i have tested packs that are colder than that is they still work; the hitachi DS 14DFL would not even work at that temp, let alone finish any application.
I see you have done a lot of testing before, so try it out yourself, place a fully charged pack in your freezer for about 3hrs and then see if you can complete any applications
