RE: cold batteries?
The cold slows the chemical reaction that makes batteries what they are. A friend crashed a small plane that the radio used dry cells. Brand new cells but left out in his truck overnight and put in the radio at the field. When everything warmed up after the crash during the crash investigation, it came back to life. Charging cells does warm the batteries; I still use wall warts so they can be still plugged in before I load the car. I would be more worried about dry cells than rechargeable.