Laptop computers have widely varying run times, with some lasting only a few hours while others can run all day. If your PC loses power in under an hour, however, you probably need to replace the battery. Starting with Windows 7, the system will notify you when your battery’s lifespan goes under 40 percent of its original strength, indicating a need for replacement. All batteries go bad eventually, but taking preventative action can keep yours running longer.

Battery Lifespan

All rechargeable batteries lose their capacity to hold a charge over time. This loss in power occurs gradually, so you may not notice it at first, but within a few years after buying your laptop, you may start to see your computer losing power very quickly. Unfortunately, you can’t repair an old battery -- if you need your computer to last longer, you will need to buy a new battery.

Preserving Your Battery’s Health

Taking care of your battery can prolong its lifespan. Heat plays a major factor in causing a battery to lose its ability to hold a charge. If your laptop gets hot during use, take out your battery when running on AC power to prevent the battery from overheating. You should also make sure to use the battery regularly: run the battery through a full charge cycle at least once a month to keep it in good shape.

Battery Calibration

If your computer dies suddenly when your battery seems to have power left, you may need to recalibrate the battery meter. Many laptop manufacturers include a calibration tool, so check your computer’s manual for specific directions. If your computer doesn’t have such a tool, you can calibrate the battery manually by charging the battery completely, setting Windows not to sleep due to inactivity and then leaving the PC running until it shuts down automatically.

Other Causes of Battery Drain

Aside from actual problems with your battery, your laptop may shut down faster than expected if you run power-intensive programs. Computer games, for example, require much more power than browsing the Web or typing a document. You can also reduce power use by turning down the screen brightness and by not using your disc drive. If your laptop has both integrated and discrete graphics processors, use integrated graphics whenever possible to save power.