Batteries

Batteries are something of a conundrum. On the one hand, there is the continuing need for better batteries in mobile devices, longer last, storing more energy in a smaller space and with reduced weight. On the other hand, batteries can sometimes fail catastrophically. The higher the energy density (the more energy stored per gram or per unit volume) the greater the consequences of a catastrophic failure. In fact a bomb can be considered something of a battery, lots of energy stored in a compact space. Though the reaction that releases the energy is not reversible and it is hard, though not theoretically impossible to power a car with gunpowder (per Huygens), it is an efficient energy storage device. Today's batteries are less efficient but still share some properties with explosives, especially when they fail. With rechargeable batteries, dependent on a reversible chemical reaction, there is always the possibility that physical structures embodied in the two chemistries (anode and cathode)will bridge, resulting in a short. They can generate high temperatures, melting themselves, melting the device they are in, and potentially starting fires. This is a rare event, but, again, major increases in energy density would make a catastrophic battery failure much more consequential.

Of course, aside from better batteries, the best way to deal with battery life is to lower the energy drain. As the most energy intensive part of most mobile devices, the primary focus has been on the display and display related subsystems. Monumental progress has been made here and further progress continues to come. A second path has been to remove the mechanical components from the device, specifically the optical drive. Spinning up the drive, takes substantial energy. Further, as removable storage is more a form of communication, simply relying on the internet rather than a disc makes sense along several factors.

Battery improvements and reductions in power drain can carry battery life only so far. Most likely, in the future, there will be more ubiquitous application of wireless battery charging. However, wireless battery charging only gets rid of the power connector, not the need to access a wired power source. The original "One Laptop per Child" design had a hand crank to generate power as a wired source for the intended user set might be unavailable not just inconvenient. Of course, cars used to be hand cranked to get them started and watches had to be wound. There is another watch technology that might be relevant as well, energy harvesting. Self winding watches are less popular, as watch batteries have gotten better, but it is still viable. With improvements in micro-machining and 3D printing, energy harvesters can be mad very small and durable, I would think just the thing for a mobile device. As with better sunlight viewability, I expect someone will at least try marketing a device more adapted to actual usage models. Perhaps energy harvesting will not show up until the mobile market fully turns its attention to wearable computing.