Laptops have many components, and though they are all designed to use as little power as possible, some still require a large amount of power. The component that requires the most power is the display monitor, followed by the hard drive. This is the reason power settings center around dimming and turning off the display and shutting down the hard drive when not in use.
Another major factor that affects laptop battery life is temperature. Lithium-ion batteries, the most common type of laptop battery, are susceptible to problems caused by extreme heat. Excess heat can cause the batteries to malfunction, have a shorter battery life, lose capacity, or in the most extreme cases, catch fire or explode. Leaving a laptop in a hot car or keeping it in an area with poor ventilation, therefore, is not recommended.
When it comes to laptop battery life, one of the largest factors to affect it is the laptop design itself. For example, laptops and notebooks designed for high-end video editing or other processor-intensive tasks will use more battery power than small netbooks designed for web surfing and email. Laptops that consume the most power will need to recharge the battery more often, shortening its laptop battery life. Also, the physical design of the laptop can affect laptop battery life. Laptops that are designed to stay cooler when running will also keep the battery cooler, and as mentioned above, heat is the enemy of a notebook or laptop battery.
Lastly, all laptop batteries have a limited life. Even a battery that sits on the shelf will begin to degrade. Having to replace a laptop battery at some point is inevitable, but make sure to recycle any old laptop batteries, and keep them from ending up in a landfill, where they can leak toxic chemicals into the air or water.