1. Cold slows the chemistry
Low temperatures slow the reactions inside a battery, so it can deliver less current. A battery may seem flat, then recover once it warms up.
2. Alkaline and NiMH suffer most
Alkaline cells lose a lot of their capacity in the cold, and NiMH rechargeables lose output too. Lithium cells cope much better, which is why they’re popular for outdoor gear.
3. Keep devices warm
Carry a torch or remote in an inside pocket, not on a cold car seat. A battery that has gone flat in the cold may work again after a few minutes in your hand.
4. Don’t heat them quickly
Never warm a battery in an oven, near a fire or on a radiator. Heat is as dangerous as cold for a battery, and it can make it leak or swell.