Batteries

A great deal of technology has been developed to extend battery life and improve power management in portable systems. However, battery life is still one of the most significant complaints about portable systems. Even though power management and batteries themselves have improved dramatically over the last few years, the power needed to run faster processors and external devices has increased, leaving battery life about the same. Actual battery life depends as much on how the computer is used as it does on power-management technology. Simply put, the more you ask the computer to do, the shorter the battery life. Today, battery life is still an issue with portable system users. Most systems use one of three types of batteries.

Nickel Cadmium Batteries

The oldest of the three technologies, nickel cadmium (NiCad) batteries are rarely used today. They have a short life and are sensitive to improper charging and discharging. After being charged, NiCad batteries hold a charge very well. How-ever, their life can be severely shortened if they are not fully discharged before recharging or if they are overcharged.

Nickel Metal Hydride Batteries

Nickel metal hydride (NiMH) batteries have a longer life than NiCad batteries (about 50 percent longer) and are less sensitive to improper charging and discharging. They are also more expensive than NiCad batteries and don't hold a charge as well when not used. They usually cannot be recharged as many times. They are, however, used in most portable systems, especially those at the lower end of the market.

Lithium Ion Batteries

Lithium ion batteries cannot be overcharged, hold a charge well when not in use, and last longer than the other two types of batteries. They are also proficient at handling the heavy-duty power requirements of today's higher-end portables. Because they are the most expensive of the three battery technologies, lithium ion batteries are usually found only in high-end systems. Unfortunately, these batteries can be used only in systems specifically designed for them.

CAUTION

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Never install a lithium ion battery in a system designed for a NiCad or NiMH battery. Doing so could result in a fire.

Buying a system with a lithium ion battery does not necessarily ensure a longer battery life. Some manufacturers take the opportunity to make the battery smaller because it is more powerful, thereby saving some space inside the computer while delivering the same performance as a NiCad or NiMH battery.