No need to add battery -- if they can eliminate fans, they can make it smaller, lighter, and have longer battery life.
First, the fans use power. Eliminate the fans, and you aren't using as much power. Which means you automatically get longer battery life when you eliminate the fans.
Second, the fans exist to dissipate heat from the processor. The only way to eliminate the fans is to find a way to have the processor generate less heat. And the only way to have the processor generate less heat is to have it use less power. And if it's using less power, then your battery life is lasting longer.
If they can get rid of the fans, then by definition they can also make it smaller, lighter, and still have longer battery life.
06-02-2015 03:19 PM