Apps, Thin Designs, Sensors Among Factors Straining Smartphone Battery Design

Larger screen sizes, thinner handset designs that limit battery size, higher processor power, HD graphics, a growing number of sensors and longer waking hours for smartphones are contributing to battery drain that can compromise the smartphone experience, Spencer said. Without advances in power efficiency and industry standards, an already challenged situation will be compounded, he said.

While mobile devices revolve around user-generated use, “soon we'll be moving into a much more immersive computing experience,” in which devices will know users’ location as well as their context, Spencer said. Devices will be aware of a user’s personal choices and will “prompt and anticipate usage,” he said. Beyond that, devices will be even more integrated into our lives through more sensors and integration of big data, he said, and that will require devices to be “always on,” requiring more power.

Wearables are an example of a growing industry category dependent on efficient portable power, Spencer said. They have to be small and always on while being able to subtly integrate into a user’s daily life.

"People want wearables to be almost invisible, and that puts pressure on battery size,” he said. The old habit of charging a device overnight when it’s not in use is no longer relevant, Spencer said. Sleep and heart-rate monitors have to be worn and working at all times, he said. Those kinds of devices now have a battery life of two to three days, but the charge life needs to extend to two to three weeks or even a month to fit the use case. “That’s simply not possible” without major advances in battery technology, Spencer said.

Some 50 percent of wearables “end up being largely unused,” due to battery charging challenges, Spencer said, and that threatens growth in one of the hottest consumer electronics categories. “If we're not careful, the next wave of innovation -- the wearable -- will end up in a drawer along with the Bluetooth headset,” he said.

Even the measurement of battery life as it relates to mobile devices is outdated, Spencer said. Smartphone batteries are rated by talk and standby time, which Spencer called “completely redundant metrics” because voice “isn’t really why you buy your smartphone anymore.” He cited a “huge shift” from a voice- and text-based mobile phone world to one that’s dominated by integrated chipsets and processors. Standby time “doesn’t exist because your phone is always chatting with the network,” he said. “There’s no such thing as standby time” anymore, he said. He said the industry needs to develop new metrics that better represent today’s smartphones and how consumers use them.

Worldwide data usage on smartphones will continue to grow as higher capacity networks emerge. ABI predicts mobile data usage will jump by six times during the period, driven by faster 4G networks and smartphone growth. Smartphone penetration among mobile subscribers worldwide is 24 percent, according to ABI, and that potential will continue to drive mobile data, he said. Counting tablets, smartphones, PCs and connected devices in the Internet of Things, ABI estimates there are 10 billion connected devices in the market, and the number is expected to touch 30 billion by the end of the decade.

Spencer called the app ecosystem a “phenomenon of our time” that has driven up data usage and diversity of data usage. According to ABI, the installed base of smartphones worldwide is 1.7 billion, the typical number of apps on each phone numbers 25-40 and in a standard day, smartphone owners launch eight apps, “some of which are never turned off,” Spencer said. He referred to the number of times those apps “ping” networks per hour checking for updates depending on how the app is configured “and how chatty it is.” If an app pings a network every 30 seconds for updates that’s more than 100 times an hour, he noted, and that frequency isn’t likely to abate as app developers want to continually engage the eyeballs of the consumer throughout the day.

Background phone activity is another area affecting battery life, Spencer said, recounting his own accrual of data charges when he travels abroad. His phone is “just sitting in my pocket,” and he gets text messages alerting him to a data overage charge due to “constant network signaling activity” in the background.

On the hardware side, thinner handsets -- as shallow as 6 mm in some designs -- require thinner batteries and that limits battery life, Spencer said. A key variable in battery efficiency is processing power, which continues to increase in what he called an “arms race.” The cutting edge of processing for smartphones is at eight-core designs, and Apple set a power target of 64-bit processing in the iPhone 5, he said. Higher processing power has enabled better quality graphics, another drain on battery life even with the implementation of architectures designed to maximize battery usage, he said.

Display size and pixel density have grown in the smartphone era and with premium phones from most handset makers now at five inches, with Apple likely to increase to that size with the iPhone 6, Spencer said. Globally, the average screen size for smartphones has moved from 4.2 inches in 2013 to 4.4 inches this year and both resolution and size have a “big impact on battery drain,” he said. The retina display phase was a step up in resolution and 4K screens for smartphones are on the horizon, he said.

User storage and RAM are on a growth curve, too, as a result of faster 4G networks that are enabling HD video, gaming and imaging, all of which contribute to battery drain, Spencer said. Cameras have been a major area of competition for handset makers with the Nokia Lumia 1020 setting an image size bar of 41 megapixels. Larger megapixel image sensors on a smartphone are about “more than just a lens and megapixels,” he said. Both the hardware accelerators used for cameras and the embedded image optimization software increasingly used in smartphones are also taxing power sources, he said.

The sheer number of sensors to enable apps for health monitoring, navigation, weather and more uses also demand their share of the smartphone power reserve. Spencer cited the Samsung Galaxy S5 as the current benchmark for smartphone sensors with nine: accelerometer, gyroscope, proximity sensors, compass, barometer, temperature, humidity, gesture and a heart rate monitor. “It’s extraordinary what’s packed into these devices,” he said.

While hardware and software power demands for smartphones have soared and batteries have shrunk to accommodate thinner designs, advances in battery technology haven’t kept up -- only doubling in battery life in the past seven years, Spencer said. Current battery design is “very much coming to the end of its growth cycle because it’s reaching its limits in technical and physical options,” he said. Larger screen sizes have enabled larger batteries but there’s a limit to that growth because a smartphone has to be “pocketable and comfortable in the hand,” he said. “You can no longer expect screen size to boost battery power,” he said. Technically, he said, there’s a limit to the number of lithium ions that can fit in a graphite-based anode, which is the industry standard for battery design. “We can’t expect even 10 percent growth in battery life with current technology,” he said.

Next-gen battery designs are in development, but they're not short-term solutions, Spencer said. Technologies in development using silicon could increase battery life by 40 percent and provide much faster charging. Charging technologies, too, are due for a shake-up, he said. Wireless charging could be “interesting” and “a help” to overall portable device power needs, he said, but added, “you don’t want to have to be charging all the time.”