Get the most from a single charge

Ever run out of battery power in the middle of an important meeting or a long flight? Even with advances in battery technology, your mobile PC can last only so long on a single charge. The trick is to squeeze the most out of the power that's available.

Chances are, you already have ways to make sure your mobile PC always has power. Maybe you carry an extra battery or your power cord so you can recharge your mobile PC whenever a power plug is handy (always consult your manufacturer's instructions for the best way to recharge your battery).

When those strategies fail, here are some other ways to help stretch your computer's battery life.

Choose a power plan that saves power. A power plan is a collection of hardware and system settings that control how your mobile PC manages power. Windows Vista has three default plans:

  • Balanced. Offers full performance when you need it, but conserves power when the computer is idle.

  • Power saver. The best choice for extending battery life. The cost? Slower performance.

  • High performance. Maximizes system performance at the expense of battery life.

To change your power plan

  1. Click the battery meter icon, located in the notification area on the Windows taskbar.

  2. Select one of the three default power plans: Balanced, Power saver, or High performance.

You can also create your own custom power saver plans. For more information, see Power plans: frequently asked questions.

Reduce display brightness. The display can use more power than any other computer hardware—even more than your hard disk and central processing unit (CPU). Some mobile PCs have a dedicated button or dial to change the display brightness (check the information that came with your computer or visit the manufacturer's website). You can also often adjust the display brightness from Windows Mobility Center. Windows Mobility Center is available in Windows Vista Home Basic, Windows Vista Home Premium, Windows Vista Enterprise, Windows Vista Business, and Windows Vista Ultimate. For more information, search for “Windows Mobility Center” in Help and Support.

Shorten the length of time before Windows turns off the display. When you're not using the mobile PC—even for brief periods of time—you can save power by having Windows turn off the display after a period of inactivity.

To choose when Windows turns off the display

  1. Open Power Options by clicking the Start button Picture of the Start button, clicking Control Panel, clicking System and Maintenance, and then clicking Power Options.

  2. On the Select a power plan page, in the task pane, click Choose when to turn off the display.

  3. On the Change settings for the plan page, next to Turn off the display, choose the display and sleep settings that you want to use when your mobile PC is running on battery and when it's plugged in.

  4. Click Save changes.

Turn off or remove devices that you aren't using. Many universal serial bus (USB) devices use power just by being connected. If you use a USB mouse, you can save power by disconnecting the mouse and using a touch pad or tablet pen. If you use a USB flash drive, unplug it when you're not using it.

Turn off PC cards and integrated wireless devices. These devices also use power. If you don't need them while you work, turn them off.

Think of your mobile PC as a car and the battery meter as the car's fuel gauge. The faster you drive, the more fuel your car's engine consumes, and the fewer miles you can travel on a tank of fuel. Similarly, doing things on your mobile PC that require lots of power drains the battery faster, so you won't be able to use your mobile PC as long.

How accurate is the battery meter?

The battery meter is not completely accurate at every moment. A mobile PC's power consumption varies, depending on what you're doing and how long you spend doing it (for example, watching a DVD consumes more power than reading and writing e‑mail). Therefore, the battery meter can lag in reporting the charge and the estimated time remaining. Also, as a battery ages, a full charge is represented as less than 100 percent, and older batteries can drain faster than newer ones.

The accuracy of what the battery meter reports—what percentage of a full charge remains and how long you can use your mobile PC before you must plug it in or replace the battery—depends on several factors. Most of these factors fall into the following two categories:

What you use the mobile PC for. Because some activities drain the battery faster than others, alternating between activities that have significantly different power requirements changes the rate at which your mobile PC uses battery power. This can vary the estimate of how much battery charge remains. The time remaining on the battery meter depends on what you're currently doing, and is likely to change depending on what you do next.

Battery hardware and sensor circuitry. Most mobile PCs use lithium-ion (Li-ion) batteries. Like most batteries, lithium-ion batteries gradually lose their capacity to store energy as they age, whether or not you charge them. Over time, this change in storage capacity significantly affects the accuracy of the battery meter.


  • If you frequently drain and then recharge a lithium-ion battery, it can quickly lose its ability to hold a charge. The practice of completely draining and then fully charging a battery is advice that applied to nickel cadmium (NiCd) batteries and, to a lesser extent, nickel metal hydride (NiMH) batteries. Lithium-ion batteries last longer if you charge them often, a little at a time, to maintain a minimum charge of about 40 percent capacity.

Other factors that influence the accuracy of the information on the battery meter are the circuitry that measures variations in battery temperature and power consumption, and the equations that the circuitry uses to estimate the remaining charge and time. Newer, "smart" batteries are equipped with circuitry that calculates these measurements and reports the information to the battery meter. Older batteries use less sophisticated circuitry and might be less accurate.

If your mobile PC battery can no longer hold a charge, or if you find yourself recharging it several times a day, consider replacing the battery.

These tips can help you get the most use from a single battery charge and avoid the inconvenience of a dead battery.