Laptop computers allow us to remain connected to our friends, family, and entertainment on the go, without being tethered to the wall, as is the case with desktop PCs. To enable this, every laptop has an internal battery that must be charged in order to keep the computer running.

Standard Laptop Battery Charging

Every laptop computer includes a power adapter---a small plastic box with cables extending from it. One cable should be connected to a power outlet, while the other is connected to the back or side of the laptop. While the battery is charging, an indicator on the bottom (Windows) or top (Macintosh) of the screen will show the current charge level of the battery. When the battery is full, the adapter will stop charging it to prevent damage. Depending on the size of the battery and specifications of the laptop, a fully-charged battery will provide approximately two to five hours of power after the power adapter is disconnected. Many laptop batteries are removable, and can be taken out of the laptop using a plastic release switch on the bottom of the unit. This allows the battery to be changed and replaced with a space, which can be an enormous benefit when a great deal of time is spent away from a power outlet. A spare battery can be purchased from the manufacturer of the laptop.

Alternative Charging Methods

It is worthwhile to consider an alternative method for charging the battery in a laptop if the computer is frequently used for long periods without access to power. Solar panels have been adapted for use with laptops, and can be purchased from companies that specialize in alternative sources of power. Laptop solar chargers are only useful in areas that receive plenty of sunlight. Additionally, it is rare for a solar charger to be able to power a laptop fully. More often, a solar charger will merely extend the amount of time in which a laptop can run before the battery dies. An external battery pack may be a more versatile method for keeping a laptop charged. An external laptop battery can be charged from any wall outlet, separately from the laptop itself. When the laptop's battery is close to dying, the external battery can be plugged in. An external laptop battery both powers the laptop and charges the internal battery, adding several hours to the laptop's battery life.

Source:

Power to the People: CNET's Guide to Laptop Batteries

Universal Laptop Batteries

Voltaic Generator Solar Laptop Charger