Infoworld published 10 power-saving myths debunked. I admit that I assumed this myth was true.
Myth No. 7: Notebook batteries just wear out. There’s not much you can do to make them last longer.
Fact: Many laptops with nickel-cadmium batteries come with a battery-reconditioning utility that drains the battery fully, then brings it back to a full charge. Laptops with lithium-ion batteries aren’t afflicted with the same memory problem as those powered by NiCad batteries. However, unlike NiCad batteries, lithium batteries prefer to be only partially discharged: Running them all the way down will shorten their life span. The calibration utility for lithium batteries actually just re-calibrates the capacity measurement to reflect the loss of capacity over time; it doesn’t affect actual battery life. Battery life for either type of battery can be prolonged greatly by removing the battery when the unit is plugged into AC power. This approach is recommended if your laptop supports it and power outages are infrequent in your area.
Since my last laptop battery cost well over $100, I will certainly be pulling the battery out of the machine when it is on AC power. Since most cell phones use lithium-ion batteries, I presume that the advice about not letting them run all the way down applies to cell phones as well as to laptops.
