Like all rechargeable battery packs, laptop batteries eventually lose their ability to hold a full charge. Although it's not possible to make a battery pack perform like new again (unless the cells are replaced), it is possible to improve cell performance by reconditioning or calibrating some laptop battery packs.
Insert the battery into the laptop. Plug in the laptop and allow the battery to fully charge. Restart the computer.
Disable hibernation temporarily. In Windows XP, for example, click Start, then "Control Panel," then "Power Options." Select the "Hibernate" tab, then uncheck "Enable Hibernation." Click "OK" to save the settings.
Change settings to discharge the battery. Click on "Control Panel," "Performance and Maintenance," "Power Options" and then "Power Schemes." Make a note of the settings under the "Plugged In" and "Running on Batteries" columns so you can reset them later.
Set all six options to "Never" from the drop-down lists. Click "OK" to save the settings and disable power management.
Unplug the laptop, but do not turn it off. Run the laptop until the battery is completely discharged (the Power/Standby light will blink) and the laptop shuts down.
Plug the laptop back in, allow it to fully charge again, then restart the computer. Enable hibernation and enter your original performance settings in "Power Schemes."
The battery pack will charge faster if you are not using the laptop. Turn the computer off for best results. Also, clean the metal contacts on the battery with a soft cloth to improve power transfer.
Do not calibrate lithium-ion batteries. Other types of laptop batteries, such as NiMH and NiCad, should not be calibrated more than once a month to avoid damage to the circuitry.