People are facing the battery problem on laptops. It's also expensive to get new battery time to time. So it's better if you use these tips to help your laptop's battery power last longer.
Laptop Battery TIPS
1. Unplug external devices such as a USB mouse or an external drive. Eject the external devices like pen drive, DVD, Hard disk etc. if not in use.
2. Turn the volume level down, or mute it, if you do not plan to use it.
3. Reduce the LCD's brightness level. If you use your laptop in a well lit area or outdoors on a sunny day, try setting it at two or three bars.
4. Disable Bluetooth. If you don't use this device, you can safely disable it to avoid draining your Dell Inspiron 1545 Battery.
5. Learn to single-task. PC memory that is in-use takes more power to hold data. Also, using more memory might mean using more swap or virtual memory space on your laptop's hard drive. All of this puts an additional drain on your hp laptop battery. Instead of leaving multiple applications and windows open, use only what you need at any given time. If your laptop has plenty of memory, then keep multiple applications open to avoid loading repeatedly from the hard drive. Close all the applications that run in the background on your computer like your PDA syncing software or USB hard drive backup software.
6. Run simple applications that don't use much RAM, disk drive or processing power. Need to write a letter? Use a basic text editor rather than the processor and RAM heavy Microsoft Word. Graphics heavy applications like games or movie watching are especially hard on the HP COMPAQ NC6400 Battery.
7. Avoid extreme temperatures. Batteries rely on basic chemistry and will die faster at extreme temperatures. Try to charge and use the battery at room temperatures. 
8. Use the power management settings on your computer that come built in. On Windows xp, click "Power Options" in your control panel. On a Mac, look for "Energy Saver" in System Preferences.
9. Switch off the wireless card if you do not plan to access your network or Internet connection. For Mac laptops, there is a button for powering on and off your wireless device is found on the toolbar at top.
10. Shut down or hibernate the laptop rather than using standby HP Pavilion dv2000 Battery, if you plan on not using it for a while. Standby continues to drain energy to keep your laptop ready to go when you open the cover.