The rechargeable batteries used in some older laptops suffer from a problem known as the memory effect. This means that the capacity of the battery becomes artificially reduced, in turn cutting operating time. Recalibrating can restore the ability of the battery to carry a full charge.
Check if your model has a recalibration program from Dell. The Inspiron 5000, 7000 and 7500 models can use a program named I75BRCA0.EXE while the Latitude LM and Inspiron 3000 and 3200 models can use a program called BATRECAL.EXE.
Make sure your laptop is connected to the Internet. Download the appropriate program from the Dell Download site (See Resources).
Close all other applications, make sure you have plugged your laptop into the mains, then run the recalibration program. It can take some time, so it may be sensible to run it overnight.
Check if your model has a recalibration utility built-in. The Latitude LS, L400 and X200 and the Inspiron 2100 models have the utility.
Restart the system and press the "F2" key when you see a message reading "Press F2 to enter Setup." If your laptop loads up Windows, restart again and continually tap the "F2" key during the boot process until your get to the BIOS screen.
Press the right arrow key to access the Power page of the BIOS menu. Press the down arrow key to select either "Run Battery Learning" or "Battery auto-learning", whichever is listed. Press the minus key while the option is highlighted to start the recalibration. Follow the on-screen instructions to complete the process.
Fully charge your laptop by plugging it into the mains and waiting until the battery indicator shows full. Keep you laptop turned off to speed up the process.
Unplug the laptop from the mains and use it until it is completely out of power and automatically shuts off. Be careful not to work on any important projects when the battery is close to running out. Increase the contrast on your screen and play videos if you want to speed up the process of draining the battery.
Plug the laptop back into the mains but don't turn it on. Wait until the battery indicator is full.
Many newer Dell laptops have batteries that don't suffer from a memory effect. If you have battery life problems on a newer model, or if the recalibration method does not work, you may have another problem with the battery and it could need replacing.
Do not use a recalibration program that isn't designed for your model. This could invalidate the warranty on your laptop.