Battery technologies explained

With four battery technologies onstage and one waiting in the wings, there's sure to be a battery to suit your needs.

Although all batteries are not created equal, they all have the ability to turn chemical energy into electric current to power electronic devices--from tiny digital music players to big notebooks. As with the battery in a car, a chemical reaction inside a notebook's battery frees electrons to flow from the positive terminal to the negative terminal, creating enough current to run the device.

That was then
The old-timer of mobile battery technologies is the nickel-cadmium cell (NiCd), once the mainstay of laptop design. Unfortunately, NiCd cells can carry only enough power to run a system for about an hour, and they contain toxic cadmium which makes them hard to dispose of.

Despite their ability to be recharged about 1,000 times, nickel-cadmium cell batteries also suffer from something called "memory effects"; over time, they lose the ability to hold a complete charge. Luckily, lighter and more powerful battery designs have surpassed the NiCd, and today, NiCds are used mostly in toys and inexpensive cordless phones. About a decade ago, most notebook makers switched to nickel-metal-hydride batteries (NiMH). Not only can these batteries hold about 40 percent more power, they aren't as susceptible to memory problems as NiCds are, and they are more environmentally friendly. On the downside, you can recharge NiMHonly about 200 times versus 400 charge cycles for newer designs.

Chemistry	Peak watt-hours/number of recharges	Problems	Main use
Nickel-cadmium (NiCd)	80/1,000	Heavy for the power it holds, memory effects, contains toxic elements	Toys and cordless phones
Nickel-metal-hydride (NiMH)	120/200	Moderate weight for power, limited lifespan	Rechargeable batteries, older notebooks and mobile phones
Lithium-ion (Li-ion)	160/400	Hard to manufacture, expensive	Notebooks, handhelds and cameras
Lithium-ion polymer (Li-poly)	130/400	Hard to manufacture, expensive	Mobile phones and backup batteries
Fuel cell	N/A	Experimental, expensive	Space shuttle, power plants and automotive research

This is now
Today, the lithium-ion cell (also known as Li-ion), which holds roughly twice the capacity of a nickel-cadmium battery, rules the notebook battery roost. Used on most laptops, handhelds and mobile phones, lithium-ion technology can hold a lot of power, but its exotic materials make it expensive. Part of the credit for its success goes to a tiny controller chip embedded in each battery that adjusts how quickly the battery discharges and prevents it from overcharging.

Lithium polymer
Lithium-polymer (Li-poly) technology has already made its way into high-end mobile phones, handhelds and notebooks. Extremely light and malleable, these batteries are capable of providing nearly as much power as lithium-ion cells, but can also be shaped to fit into a device's hidden nooks and crannies.

Tags: Notebook, Sony Vaio, Laptop Computer, fuel cell, Sony Corp.