Outside of actual machine performance, battery life of a laptop is a huge selling point. After all, what is the machine worth if it lasts less than an hour off the charger? One way to increase the battery life of your notebook is to simply well, increase the size of the battery itself. However, size isn't the only factor when it comes to buying a new battery.

The first thing you should look at is actually not the laptop's battery. Take stock of your machine. Are you using a netbook, a notebook, or a desktop replacement PC? A netbook will usually have a fairly miniature screen, approximately 10 inches. A notebook will have a 14-15 inch screen, and entertainment notebooks or desktop replacement PCs will generally have 17 inch or larger screens. This is not conclusive, as the type is more defined by specifications and hardware, but it is a good general rule as it applies to power consumption. Smaller screens take less electricity to power, and a smaller machine also generally has smaller, less energy demanding hardware. A netbook battery like the Toshiba NB205 6 cell battery can last three times as long on the same capacity battery in a standard notebook under the right conditions; this is mainly due to the scaling down of the parts in the Toshiba NB205 versus that of a full sized notebook. Some entertainment notebooks and the like are not made to function for extended periods on batteries, rather they are meant to spend most of their time on their adapters, only functioning on backup power rarely as needed.

Once you know what you're working with, assess where you need to take it. If you're just typing papers for school on the machine, chances are you can find an outlet in your library or somewhere at home or on campus. However if you're taking notes throughout all your classes, you may have less reliable access to outlets, and you will potentially be on battery power for a few hours at a time.

When purchasing an upgraded or replacement battery for your machine, the cells will be what indicate potential longevity. Three cell batteries aren't widely used as they last for nearly negligible amounts of time off AC power. Six cell batteries and nine cell batteries are progressively more expensive, but they will power your machine two and three times longer than a three cell battery, respectively. They are also the most common sizes of battery purchased by consumers. Twelve cell batteries are available for heavy users, but can become sizably more expensive than others.

Keep in mind also that nine and twelve cell parts become progressively larger, adding bulk and weight to your machine and making it that much less portable or easy to take with you on the go. In these cases, you may want to consider simply carrying a second battery. Whichever choice you make on your laptop battery purchase, use a knowledgeable and high quality laptop battery supplier to be sure you get a fully compatible battery.