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Why your smartphone battery doesn't last

Lithium ion batteries are nearing the limits of their possible power capacity.

If your awesome new smartphone is to have any hope of lasting longer than a day on one charge, it's going to need more power than a typical lithium ion battery can deliver.

Used to be, you could forget your feature phone’s charger at home, go on a long-weekend vacation, and--assuming that you didn’t use it to play hours of Snake--still come home with enough battery life left on it to call a cab.

Today, though, we’re wedded to our chargers, and glare hawkishly at people who hog airport and coffee-shop outlets for too long. Switching over to superfast 4G networks, as many smartphones will in 2011, is only going to exacerbate this problem; and reports already indicate that 4G devices tend to have pitiful battery life. In fact, the power requirements of the technology being built into mobile devices is growing at twice the pace of battery-capacity increases, according to one Verizon executive.

But catching up with mobile power requirements won’t be quick or easy for the battery industry, and continuing difficulty may discourage public adoption of new 4G devices. Unfortunately, the problem isn't a simple matter of mobile battery R&D falling behind. It extends to the chemical nature of batteries, the way research and development is funded in the global market for mobile tech, and the many different demands users place on our phones and tablets.

Constrained by Chemistry

Battery technology and smartphone technology are at two very different stages in their lifespans. “Unlike smartphones, battery technology has been evolving for over a century, and is much further down the development curve, meaning that improvements in battery technology, while steady, no longer happen at the breakneck speed of younger technology like smartphones,” says Keith Nowak of phone and tablet maker HTC.

But aside from tiny incremental improvements in solid-electrolyte efficiency, lithium ion polymer batteries for handheld tech products haven't changed drastically in more than 15 years. Almost all of the batteries that power today's smartphones and tablets run on some variant of the lithium ion polymer battery--a cell in which the anode and the cathode are packaged with a solid, gel-like electrolyte (the substance that makes the battery conduct electricity). This solid-electrolyte design was developed commercially in 1996 as manufacturers sought a sturdier battery for mobile tech products. Previously, cell phones had run on lithium ion batteries with liquid electrolytes, which were bulky and relatively unstable.

Today, battery researchers continue to increase the capacity of lithium ion polymer batteries. Since a battery’s power comes from its transfer of electric-charge-bearing electrons between the anode and the cathode, battery researchers focus primarily on optimizing the multitude of mini-transfers. “A lot of chemical reactions can take on a life of their own, and battery scientists try to control that,” said Irving Echavarria of Gold Peak Industries, a company that manufactures all types of consumer batteries, including lithium ion variations. Echavarria estimates that 80 percent of the processes in a battery can be accurately harnessed. And the smaller the battery’s window of errant chemical reactions, the more efficiently the battery will provide power. Battery makers continue to achieve capacity gains by pushing closer to that 80 percent efficiency limit.

But the incremental advances in efficiency aren’t keeping pace with the increasing energy demands of smartphones and other mobile devices. Frustrated by the chemical and physical limits of batteries, developers who want to get longer run times out of smartphone batteries must either add active material to the battery by making the inactive parts of the battery smaller (a technique that has already reached limits of its own) or move from lithium ion polymer to a different, as yet not fully researched material.

Venkat Srinivasan, a battery technology researcher at the Lawrence Berkeley National Laboratory in Berkeley, California, notes that, “the physics that dictates evolution in batteries is different from the physics that dictates evolution in smartphone electronics.” It seems that batteries are doomed to drag along behind the wagon train until a Eureka moment happens occurs with a better material.

New Ideas Coming, Slowly

Small signs of innovation are visible on the battery-life horizon. The unanswered questions are how quickly they’ll emerge, and whether the technology involved will be scalable to serve the entire mobile world.

Lithium ion research continues in the R&D labs of many consumer-battery makers. And university labs across the country have churned out paper after paper on the possibilities of graphene, a single-atom-thick sheet of graphite that has the potential to store and transmit energy (though any use of graphene for consumer batteries is still a long way off). But the U.S. government (like many other national governments) has provided almost no funding for consumer battery research, instead putting money into research for vehicle and military-use batteries.

It’s Not Just the Battery, Though

Designing a mobile device is no longer just about perfecting its computing power, design, and user interface; it’s about doing all those things with far less power. At some point, consumers’ desire for faster data plans and monster multitasking capabilities will be overtaken by the simple need for a device that can remain in operation for at least one full workday.

Smartphone screens are getting larger and supporting higher resolutions, both of which suck power like crazy. Lowering your screen's brightness might help eke a few extra minutes out of your battery, but Apple, HTC, Motorola, and other major phone manufacturers are unlikely to move to smaller or duller screens anytime soon. Nevertheless, some (including Samsung and LG Electronics) are focusing on making new types of displays that are no dimmer but use less power.

Another major power drain relates to increasingly complex apps, which impose ever-steeper processing requirements. Most smartphones contain Bluetooth, Wi-Fi, and GPS radios inside, and in many instances these components operate simultaneously. The GPS radio, in particular, is a notorious battery killer: You can see the battery bar getting shorter as you run your navigation app. Newer phones add a 4G radio chipset, which requires a lot more processing power to decode far greater amounts of data encoded in the LTE wireless spectrum. On top of all that, new 4G phones have two different chip sets, to connect with a 4G spectrum and with the carrier’s older 3G network. As a result, you can count on your battery to deliver only about a day of juice to your phone, if you're lucky.

One consequence of runaway power consumption is that the makers of mobile processors are feeling a lot of pressure to produce more-efficient chips for phones.

James Bruce, an executive at ARM, which develops and licenses processors for almost all mobile devices in the world, explains that phone hardware is much more battery-efficient today than it was when phones lasted longer, but "the difference between a Nokia [feature phone] and a smartphone today is that there just wasn’t enough there for people to keep using their phones all day."

Dual Cores Will Help

The dual-core processors (made by ARM) that have shown up in a few 2011 smartphones (auch as the HTC Droid Bionic and the Motorola Atrix 4G) may offer some hope. According to Bruce, "dual-core” phones can delegate simple tasks to one core, while directing more-complex (and more-power-hungry) tasks to the other core. As Bruce explains, if the phone is doing only simple tasks--such as sending text messages or running the calculator--on one core, the other core can power down, thereby saving battery life.

The idea that more cores could be the secret to using less battery power may seem a little counterintuitive, but ARM isn’t the only company trying to solve the problem of too-short battery life in that way.

At the beginning of May, a company called Adapteva announced their new "Epiphany Microprocessor," which they hope to place in smartphones and tablets alongside ARM dual-core processors.

Adapteva’s new processor can accommodate up to 64 cores on a smartphone chip. While planting a 64-core chip in a smartphone sounds like the opposite of a power-saving measure, Andreas Olofsson, CEO and founder of the company, says that most smartphones today run a scaled-down, power-hungry version of a desktop processor to connect to the Internet, run games, and play music.

The Epiphany processor, on the other hand, is a chip optimized for performing specific parts of general commands in tandem with the phone’s CPU (which does all of the phone’s general processing). The processor can streamline the offline duties of the phone to make gesture and facial recognition faster, for example. Olofsson says that this design could "put the power of a laptop in a smartphone today."

It’s the Apps

Smartphone apps are the final culprit in our rogues' gallery of smartphone battery killers (with the physical limits of batteries ranking as the first culprit). An app's power usage is one of the things Apple examines when deciding whether to approve an app for sale at the App Store. “[Apple] wouldn't let you intentionally ruin battery life, like if you were running a game that didn't require GPS, they would reject the app if it was pinging a GPS signal every 10 seconds,” says Cameron Vanga, a developer with iPhone app maker 9magnets.

Though the Android app market might harbor a larger number of potential power-sucking apps, more-established developers usually make an effort not to use more battery life than they need to get the app to function properly, for fear of receiving low ratings or having users delete the app. “Beyond maybe GPS applications, most users are good at correlating which apps are going to kill battery,” Vanga notes.

Most smartphone users are okay with taking their phones out for the day and then plugging them in to a charger each night, but battery makers are going to have to step up soon to deal with the voracious appetites of the miniature computers that everyone is relying on more and more every day. If innovation in battery technology doesn’t pick it up a little, the breakneck speed at which mobile tech innovation has been racing along could come crashing to a halt against a usability wall.

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