From fitness to health monitoring devices, wearables have become a big part of many consumer’s daily lives. And while current technology continues to improve, there are still many obstacles that must be overcome to enhance the overall user experience.
Battery life is one such problem that limits how wearables can be used due to the need to frequently recharged or replace the battery in these devices. Fortunately, recent advancements in lower power consumption technology are changing what’s possible for the future of wearable devices.
The Problem with Batteries
In the past five years, the number of connected devices in circulation has increased by over 20 billion. By 2020, it is estimated that over 50 billion devices will be in use. And while that’s exciting for the potential of wearables and the impact they will have over consumer’s lives, the need to replace billions of batteries every year and constantly charge throughout the day is a big problem that needs to be addressed.
One reason for this is the recent advancement in wearable technology. While older sports wrist wearables had very basic functions like a stopwatch, alarm, and calendar contained a battery that would last for up to three years, current models from Garmin and Suunto are much more complex wrist-based computers and need to be charged much more frequently.
High resolution color displays, activity trackers, heart rate monitoring, GPS tracking, and Bluetooth radio are just a few of the functions that require more battery power to operate. Though the battery life of high-end wearables has drastically improved recently, there is also more pressure within the industry to create smaller, thinner designs. Since batteries are what take up a majority of the space within a wearable, battery and chip size is commonly compromised in favor of sleeker designs.
When you factor in new functions such as cellular radios, new bio sensors, and additional sensor analysis constantly being added each year to these devices, there’s even more strain being placed on battery power to operate each of these additional features.
Understanding Possible Solutions
When you take a look at mobile computing improvements over a 10-year period, battery energy density has seen much less progress in terms of technology when you compare it to elements such as disk capacity, CPU speed, available RAM, and wireless transfer speed.
To begin understanding how battery technology can be progressed, it’s important to not only look at the energy being delivered to the system but also the components that are consuming energy. When power consumption from components such as display, processors, sensors, radio, and the power management system are totaled, it’s easy to see why there’s a big problem—particularly in use cases when you want clothing wearables to have enough battery power to last a year or more.
The good news is there has been some notable progress developing over the last few years. One area that’s helped drive the chip power down is Moore’s Law. Similar to the progress seen in the smartphone industry, Moore’s Law has been one of the strongest drivers of energy efficiency gains because it has allowed us to consistently decrease the size of the transistors.
This means you can fit more transistors on a chip, the cost per transistor goes down, and the overall performance improves. What’s commonly ignored though is that the decrease in transistor size means power consumption goes down as well. On top of that, because the transistor is faster the voltage can also be decreased. And since voltage is a primary energy knob in a system, huge energy gains are possible.
As a designer, lower power transistors mean a great deal of flexibility. Whether its performance, lower power, or less leakage, more choices mean greater freedom to design a device according to your needs. New transistor architectures are also being advanced, and because the structures themselves are much better than they’ve been in years past even lower power consumption is possible.
One of the other areas where we’ve seen incredible progress with circuit size is in dropping voltage. Sub-threshold design was first conceived 30 years ago, but Ambiq was the first to build a comprehensive platform. Conceptually, sub-threshold means that you never exceed the turn on voltage of the transistor. While it might not seem possible, the transistor can still operate in this sub-threshold region for a reduction in energy—though there are plenty of challenges that may exist and should be considered.
Where We’re Headed
Even though battery technology may be a bit slower, when it comes to processors much more progress has been made. Today, Ambiq’s Micros Apollo 2 is 29 times more efficient than the best in class processor in 2003 in terms of power consumption per unit of work. This progress will drive what wearables are capable of moving forward.
However, processors aren’t the only area where progress has been made. While radio power in the past was also a high-power consumption component, new low energy Bluetooth and ANT+ technology has shown remarkable improvements as well. When you consider duty cycling and some of the new application level approaches, the average power of wearables to maintain connection to a phone is able to get as low as the 10-microwatt range. This number has gone so low that radio is not even a factor in current wearables.
On the display side of things, there have been some interesting innovations as well. Electrophoretic displays are one that’s current being used in Amazon Kindles that is able to maintain its image even when power is removed. In the case of a wearable when the display needs to be updated every minute, the power consumption will remain very low while producing good quality images. Companies like Apple are rumored to working with emerging technology such like MicroLED displays that are extremely low-power displays and will be a dramatic improvement in terms of quality when compared to the LCD displays being used today.
New Use Cases
When power consumption gets low enough, additional capabilities of the wearable are possible. One example being tested in use cases is energy harvesting. While solar power and RF are definitely options, the new Matrix Power watch can actually harvest energy through body heat differential by using thermoelectric technology. The device still has a battery for those times when it’s not on the body and for backup situations, but how this existing technology is being used is a good example of what may be possible in the future.
Another interesting break through is with the potential for embedded coach analysis. Currently, wearables collect tons of data that is discarded because of the impracticalities involved with storage. Accelerometers, gyros, heart rate monitors, microphones, and other sensor fusion technology has the ability to provide huge amounts of analysis that isn’t currently being utilized to its full potential. As power needs drop and new use cases are introduced, a lot of the innovation you will begin to see in wearables is in sensor fusion. What we can record, analyze, and interpret for the user on the fly will continue to improve the overall user experience and help the individual understand how their body is responding to a variety of activities.
A current use case that builds on this is the intelligent wearable. Intelligent wearables involve building neural networks into devices so that they can be used for complex data analysis. Motion recognition, skill assessments, gait analysis, and emotion recognition are just a few of functions that are possible and may be included in devices in the future as power consumption needs continue to decrease and our use of sensor technology expands.
Valencell also conducted a webinar on this topic that you can see here:
If you have questions or would like further detail on any of this, please let us know at firstname.lastname@example.org.