A lithium-ion battery can usually last for between 300 and 500 recharging cycles, depending on how it’s maintained during its lifetime. You'll get the most out of the one in your cell phone if you avoid exposing it to high temperatures—the inside of your car on a hot summer day, for example—and if you use about 60 percent of the charge before you plug it in.

Lithium-ions are unlike rechargeable nickel-cadmium batteries, which are most efficient when completely spent before being recharged.

Frequently allowing your phone battery to completely discharge puts a strain on the battery and reduces its life span. On the other hand, short discharges and immediate recharges often cause problems with the accuracy of the battery's fuel gauge and its ability to report the battery's actual charge. Furthermore, consistently leaving your phone plugged into the charger after the battery is full wastes energy.

Lithium-ion batteries typically last for only two to three years. Heat and improper charging speed this aging process. For example, a full battery stored in a warm environment for one year will operate at just 65 percent of capacity once it’s put to use again. A battery stored with a 40 percent charge at room temperature will maintain 96 percent of its capacity after one year.

A rechargeable battery has its deepest impact on the environment when it finally reaches the end of its life and becomes part of the hazardous-waste stream. Based on current cell phone sales figures, it's estimated that Americans dispose of more than 60 million pounds of cell phone batteries per year. Understanding how to prolong the life of these relatively expensive and toxic batteries helps slow their rate of disposal, which is good for the pocketbook as well as for the environment.