All too often I see a familiar scene. Someone pulls their nice laptop out of a carrying case, then they proceed to set the computer on top of the case from whence it was taken. They sit the case on a desk probably for the convenience of not having to put it away, and naturally, they rest their laptop right on top of it. Little do they realize, this can have a large impact on their battery life.
Why you ask? It has to do with ventilation. On nearly all laptop computers the vents, that keep the internals of the computer at a reasonable temperature, are focused on the bottom and sides of the computer. The majority of computers have fans which create good air circulation, and allow heat to escape from through vents. The fans themselves turn on when the laptop needs to cool down, and in doing so, they draw a significant amount of power from the battery. In the end, if you can help it, you want to have your computer as best ventilated as possible, to reduce the amount of time that the fans are running.
Setting your computer on top of a case is most certainly going to create an environment with poor air-flow. In fact, most cases will readily store heat, making problems even worse — imagine putting your computer on a hot plate your fans will be running all day drawing precious power from the battery.
If a case is a bad place to set a computer, then what do you suggest? Any hard surface will do the trick better than a heat-sponge like soft fabric because it won’t block the vents as much. Most laptops are raised a few millimeters from the surface that they sit on through the use of small pads on the bottom of the laptop, often in the corners. If you sit your computer on a soft surface, the pads won’t create that vital space needed for good air circulation, and instead you’ll only perpetuate the issue. If you want to squeeze the most juice out of your laptop’s battery, find a hard, flat surface to use your computer to keep the fans running at a minimum.