What makes laptops stand apart, is their portability and ease of use, compared to desktop computers. The one thing that makes portable operation possible, is their rechargeable battery.
When the battery charging doesn't work, the laptop is no longer portable. It must function like a tethered desktop computer, if the battery doesn't get charged properly.
Most of today's laptop computers are loaded with a lithium ion battery, that provides an average life of about five hours. How long the charge on a battery will last is entirely determined by the kind of applications you are using it for. To charge the battery, an AC adapter, with specific voltage settings is required, which is supplied with the laptop.
There is an elaborate internal mechanism that controls and monitors the internal charging of the battery. At the computer operating system level, there are software programs that monitor the status of the battery and communicate it to the user. Let us have a look at ways in which the problem of a plugged in, but not charging notebook can be solved.
Fixing the Charging Problem
AC Adapter Problems
If the AC adapter is not working properly, then the charging won't occur at all. An AC adapter, with lower than required voltage settings, will not be able to charge the battery. See to it that the adapter matches the battery's requisite settings. A loose wire or internal breakdown may render the adapter useless. Replacing it might solve your problem.
Power Management Software Problem
Sometimes, the problem is merely with the software. This is the classic case, when the laptop charges when switched off, but doesn't, when the computer has booted. The software may have gotten corrupted, which might be causing the problem.
In such a case, go to the device manager section and uninstall the power management software. In case of Windows XP, uninstall 'Microsoft ACPI Compliant Control Method Battery listing' from the device manager section.
Take care that you do not install any other AC adapter driver software. Then go for a 'hardware scan', which will automatically identify the battery and reinstall the latest version of the driver again. That will restore the charging facility of your laptop.
Internal Charging Circuitry Problem
If neither the AC adapter, nor the power management software has a problem, then the problem may be with the internal charging circuitry of the laptop. In this case, there is little you can do, other than send the laptop to the manufacturer's service center.
There remains another possibility which is a bad or dead battery. Run a test. If your laptop is quite old, this could be one of the most likely reasons. Get the battery checked from the manufacturer and check if it has exceeded its predicted recharge cycle limit. It is important that you get the dead battery replaced immediately, with a new one.
If no troubleshooting methods works, it is best to send your laptop over for servicing, with a manufacturing company's service center. If you open up the laptop on your own, the warranty stands void, which means that you have to spend out of your own pocket. So, unless it is a software level problem, it is best that you let professionals handle it for you.