The option of picking up your computer and taking it with you is appealing, and laptops have come to be the computer of choice for many consumers. Laptops use little power, but what they do use you must carry with you in the form of a battery. Unfortunately, even the best batteries wear out over time, and if you make heavy use of your portable computer you might need to upgrade. There are several factors to consider before you make your purchase.
Modern laptops use lithium-ion batteries, which offer an outstanding power-to-weight ratio and fewer problems than older technologies. They're measured in milliamp-hours, or MaH, with large numbers being best. For example, if your laptop draws one amp, a 2,000 MaH battery would last for two hours and a 5,000 MaH battery would last for five. The real-world math is seldom that simple, because your laptop's power requirements vary with screen size, wireless Internet usage, DVD usage, the power of your graphics card and many other factors.
Battery Life vs. Size
Most current laptop computers are designed to provide four to five hours of battery life under normal usage, so comparing their standard batteries provides a rule of thumb for power consumption. A laptop that includes a 2,200 MaH battery probably uses less than a laptop with a 3,300 MaH battery. That's important, because higher-power batteries typically weigh more. Each battery is made up of individual cells joined together in the power pack, so extended batteries use more or larger cells and add to your weight. The largest of all are "sheet batteries," which attach to the bottom of your computer and match its size.
Assessing Your Needs
Before you make a purchase, give serious thought to your laptop and how you use it. The larger your screen, the more powerful a battery you'll need to run it. Laptops with potent graphics processors and CPUs also consume more electricity, especially when used for demanding applications such as gaming or video processing. If you seldom use your laptop's battery for more than an hour or two, most batteries will serve your purpose. If you need maximum battery life, sheet batteries can provide 12 to 20 hours' use. They can also be added and removed -- "hot-swapped" -- while you're working, theoretically providing infinite battery life.
Deciding on a battery is always a balancing act. On one hand, the more powerful a battery you have, the longer you can be portable. On the other hand, the added weight cuts into your portability, and can be downright burdensome. Most laptops have multiple power-saving features, and using them intelligently might mean a lower-powered battery would be adequate. Batteries from third-parties can be much more affordable than those from your laptop's manufacturer, potentially removing price as an obstacle. If in doubt, talk to staff at a computer store or battery-savvy retailer such as Radio Shack, or consult online portable-computing forums and websites for reviews and advice.
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