Fitness trackers, smartwatches, and other forms of wearable technology are fun to learn about, fun to experiment with, but less fun to actually wear on a daily basis. The biggest problem? Aside from a well-executed few, most wearable devices — smartwatches particularly — don’t have batteries that are powerful enough to make them both useful and long-lasting. Without better battery technology, wearable devices may never mature beyond a passing trend.
Larry Burgess reports for ReadWrite that batteries are one of the biggest hurdles in the way of the advancement of wearable devices. And nowhere is that more visible than in the current state of smartwatches, which seem to have a lot of promise. Smartwatches have yet to find their killer app (or gain the battery life to enable users to rely on apps, or simply wear them for more than a day or two without recharging). They also have yet to find a form factor appropriate for small wrists or those looking for a device that looks more like a traditional watch than a piece of technology. While battery technology continues to improve slowly, batteries are still a significant constraint as manufacturers try to make wearables with longer battery life and less obtrusive form factors.
As the number and variety of wearable devices increases, the demand for smaller and longer-lasting devices, as well as higher device intelligence, should drive the development of better battery technology. Burgess notes, “If we don’t continuously improve our batteries, the wearable industry will power down.” He notes that energy efficiency and improved energy sources are the highest priority in maintaining the growth of the wearables market, and that concern has led to the development of a number of alternative energy sources, which enable manufacturers to improve on the battery size, shape, capacity, and reliability of conventional batteries.
The starting point is lithium-ion batteries, which are ubiquitous in a huge variety of different devices. Their capacity decreases as the size of the battery decreases, and most of them are disposable, so they’re using in small devices — like hearing aids, remote car keys, doorbells, and some of the earliest wearable devices. Burgess reports that they’ll continue to be used in wearable devices where convenient battery replacement is an important feature.
Thin-film batteries use similar lithium-ion technology, and they’re used in smartphones and other handheld devices because they’re rechargeable and their form factor is better-suited to low-profile packages. Since volume determines the energy capacity of the battery, thin-film batteries take up more space than a coin cell battery. But they’re well-suited for flat wearable devices, like those that could be integrated into outerwear, or remote measurement devices that are placed in walls or furniture. Pouch batteries, in turn, are lithium-ion batteries in a pouch of plastic or polymer, and a wide variety of shapes and thicknesses are possible with that type of battery.
Graphene batteries are built on a form of carbon that Burgess says “may be the wave of the future.” They have high energy density and high storage capacity. But currently, they are much more expensive than other battery types, and have to be deployed widely so far. Supercapacitors have low charge leakage and high capacitance, and can be used as an energy source for low-current-drain wearables. Another much-hyped alternative energy source is energy harvesting, which can be used to recharge batteries or supercapacitors in wearables. The energy categories that can be converted to electrical energy include kinetic, thermal, piezoelectric, and even radio waves.
In the meantime, before alternative energy sources are ready for widespread use, some wearables and smartwatches — mainly those without power-intensive screens and an endless assortment of apps — have passable, even commendable battery life. But some users, or perhaps a different set of users, prefer a device like the Apple Watch to one of Pebble’s smarwatches. And it’s the Apple Watches of the wearables world that are trying to do more than current battery technology is really able to support.
A major complaint related to the Apple Watch has been that, even with minimal usage, its battery isn’t able to last through more than a day. Add in anything more than moderate app usage, and the smartwatch struggles to get through the work day. While Moore’s Law makes devices better at conserving battery power, battery technology itself doesn’t keep pace with Moore’s Law in the slow march toward increasing capacity.