Why Do Batteries Discharge More Quickly in Cold Weather?

By Anne Marie Helmenstine, Ph.D., About.com

Answer: The electric current generated by a battery is produced when a connection is made between its positive and negative terminals. When the terminals are connected, a chemical reaction is initiated that generates electrons to supply the current of the battery. Lowering the temperature causes chemical reactions to proceed more slowly, so if a battery is used at a low temperature then less current is produced than at a higher temperature. As the batteries run down they quickly reach the point where they cannot deliver enough current to keep up with the demand. If the battery is warmed up again it will operate normally.

One solution to this problem is to make certain batteries are warm just prior to use. Preheating batteries is not unusual for certain situations. If the battery is already warm and insulated, it may make sense to use the battery's own power to operate a heating coil. It is reasonable to have batteries warm for use, but the discharge curve for most batteries is more dependent on battery design and chemistry than on temperature. This means that if the current drawn by the equipment is low in relation to the power rating of the cell, then the effect of temperature may be negligible.

On the other hand, when a battery is not in use, it will slowly lose its charge as a result of leakage between the terminals. This chemical reaction is also temperature dependent, so unused batteries will lose their charge more slowly at cooler temperatures than at warmer temperatures. For example, certain rechargeable batteries may go flat in approximately two weeks at normal room temperature, but may last more than twice as long if refrigerated.

From: about.com