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Batteries for portable ICT devices - TechWatch Alert
Dr Martin Cooper
photo credit: Motorola
Dr Martin Cooper of Motorola is said to have made the first US analogue mobile phone call on a larger prototype model in 1973. This is a re-enactment in 2007

Starting from bricks
The world’s first commercial cellular phone, the Motorola DynaTAC 8000X (Dynamic Adaptive Total Area Coverage), received approval from the United States Federal Communication Commission (FCC) in 1983. It was also known as the “brick phone” because of its dimensions (33 cm x 4 cm x 9 cm) and weight (0.9 kg). The battery of this “brick phone” offered half an hour of talk time, up to eight hours of standby time, and took 10 hours to recharge.
 
image
Photo credit: Motorola
Prototype direct methanol fuel cell (DMFC) battery. DMFC may be the energy technology of tomorrow

The world’s first commercial cellular phone, also known as the “brick phone”, offered a half an hour of talk time, up to eight hours of standby time, and took 10 hours to recharge. Batteries are still the weak link in mobile devices, but they have come a long way. The battery life of a 3G smartphone, for example, provides more than 10 hours of 2G talk time, five hours of 3G talk time, five hours of 3G Internet time, six hours of Wi-Fi Internet time, seven hours of video playback or 24 hours of audio playback, according to manufacturers. These improvements allow for all-day use, and you can leave the charger at home.

A year after the launch of the brick phone, some 300 000 people worldwide had mobile phone subscriptions. Today, more than 25 years later, this number has passed the 4.6 billion mark. Batteries are critical to the usefulness of portable information and communication technology (ICT) devices. With ever more users going mobile, manufacturers and governments are investing in research on clean, energy-efficient and longer-lasting batteries to cater for the power-hungry features of portable electronic devices. ITU’s latest TechWatch Alert* summarizes some of the key trends and developments in battery technologies for mobile devices.

Advances in processing power and new-generation communication links have increased mobility and driven the demand for mobile phones, laptops and other gadgets, including e-books, MP3 players and digital cameras. Hybrid electric cars, which rely on on-board battery packs, are the stars of many motor shows. This was evident at the 2010 Geneva International Motor Show, where ITU/ISO/IEC jointly organized “The Fully Networked Car@Geneva Motor Show”, held on 3–4 March 2010.

ITU estimates that, by the end of 2010, there will be 5 billion mobile subscriptions worldwide. Much of this growth is taking place in the developing world, where users often need to come up with creative alternatives to overcome the lack of ubiquitous power supplies. Some kiosks in rural areas not only recharge (prepaid) units, but also batteries. Fostering the development of batteries or devices that do not solely depend on electric power grids for recharging, as well as gradually improving and expanding the energy infrastructure, are therefore essential to connecting any user, anywhere, and to bridging the digital divide.

Market research suggests that the USD 71 billion-a-year worldwide battery market (with rechargeable batteries accounting for two-thirds) could grow by 4.8 per cent annually up to 2012.

Battery characteristics

Batteries have improved in terms of energy density, but the higher power requirements of devices have eaten up the benefits of better battery performance. The net result is that runtimes stay the same. The search is on for a safe, lightweight, small size and environmentally friendly battery, with high energy density, a long runtime and a long lifetime. The breakthrough has not yet happened, but existing technologies are being gradually improved and adapted to meet the requirements of particular devices or applications.

There is no standardized procedure to provide information on battery runtimes for different ICT devices. Manufacturers and advertisers state runtimes and lifetimes, but this information should be treated with caution because it depends on usage patterns, which may vary. For example, power management settings and the use of features (Wi-Fi, DVD drive) or applications can all affect runtimes and the lifetimes of batteries.

Current battery technologies

Lithium-ion (Li-ion) and nickel-metal-hydride (NiMH) batteries are most commonly used in portable electronic devices. Li-ion batteries usually offer a higher energy density than NiMH. Also, Li-ion batteries allow for a great number of charge/discharge cycles without memory effect, which ensures a long battery lifetime. It is estimated that Li-ion batteries lose up to 5 per cent of their charge per month through self-discharge, compared to up to 30 per cent loss per month in NiMH batteries.

Form and weight are important factors in the choice of batteries in portable devices. Li-ion batteries exist in a wide variety of shapes and sizes, and are relatively light, but NiMH has advantages over Li-ion, including lower cost, high current, and no need for processor-controlled protection circuits. NiMH batteries are often found in digital cameras. Lead-acid batteries are too heavy for mobile use, and nickel-cadmium (NiCd) batteries have been banned for sale in the European Union because of their toxic components.

New energy sources for mobile devices

The need to recharge batteries compromises the mobility and autonomy of the devices they power, so manufacturers are searching for better technologies.

If photovoltaic and fuel cell technologies could be miniaturized for use in portable electronic devices, they would extend autonomy between recharges. Fuel cells systems, in particular direct methanol fuel cells (DMFCs), may be the energy technology of tomorrow. Like conventional batteries, fuel cells produce energy through an electrochemical reaction. The main difference is that, as long as the fuel supply lasts, fuel cells are constantly being charged.

Current DMFCs produce a low level of power, but they can store high-energy content in a small space. This means that they can produce a small amount of power over a long period. This would make them optimal for consumer goods such as mobile phones, laptops and cameras. The main obstacles to this use include power handling, downsizing and cost. At present, fuel cells are generally found in environments where no combustion is possible, and where toxic exhausts cannot be tolerated, for example in space vehicles and submarines.

Nanotechnology is another promising area, because the properties of nano materials could help in the development of high-performance Li-ion batteries. But before being ready for use in consumer goods, further research is required to better understand the mechanisms of lithium storage in nano materials, and to achieve controlled, large-scale synthesis of nanostructures and kinetic transport on the interface between electrode and electrolyte.

An even more recent field of research focuses on tiny micro-batteries about half the size of a human cell. These could be stamped onto a variety of surfaces, and might one day power a range of miniature devices. Nanotechnology or cell-sized battery technology have the potential to open the way for new features and start a new era for mobility.

Chargers and charging

When replacing a mobile phone, the user is usually obliged also to replace its charger, which is often not even compatible with other products from the same manufacturer.

Unusable chargers represent unnecessary electronic waste, as well as being inconvenient. As part of its work on ICT and climate change, ITU’s Telecommunication Standardization Sector (ITU–T) is moving ahead with a technical standard for an energy-efficient one-charger-fits-all for mobile phones. Developed by ITU–T Study Group 5 on environment and climate change, Recommendation L.1000 (ex. L.adapter) on “Universal power adapter and charger solution for mobile terminals and other ICT devices” provides high-level requirements for a universal power adapter and charger. This will reduce the number of power adapters and chargers to be produced and recycled by widening their application to more devices and increasing their lifetime.

Wireless recharging is an area of research aimed at replacing chargers and cables. The idea is to power mobile devices on the fly, over distances up to several metres, using non-radiative electromagnetic coupling. The technology is already able to wirelessly power devices such as DECT handsets in the range of a few milliwatts up to kilowatts.

With all these promising new technologies, the future of energy and communication for all looks bright.

 

* TechWatch Alerts are prepared by ITU’s Telecommunication Standardization Bureau (TSB) to provide a brief but concise overview of emerging technologies and trends in the ICT field. The TechWatch Alert on “Batteries for portable ICT devices” was published in February 2010. The TSB is interested in your thoughts and feedback on its reports, and open to your proposals on topics for future Technology Watch publications. Please send your comments to tsbtechwatch@itu.int.

 

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