Storage for portable devices

Keeping power on the move

By Morand Fachot

The number of portable consumer electronic devices used for entertainment, communication or computing has grown dramatically in recent decades. This growth has been made possible thanks to technological advances in the production of more powerful, energy-efficient and cheaper electronic components and devices. Another major driver has been significant improvement in battery technology itself, an important activity for several IEC TCs (Technical Committees).

Regency TR-1, the world's first commercially produced transistor radio (1954) Regency TR-1, the world's first commercially produced transistor radio (1954)

Music anytime, anywhere

The first widely popular electronic consumer product which didn't need to be plugged in was the transistor radio, which appeared in the mid-1950s. Although comparatively costly initially, its price subsequently dropped sharply, ensuring its rapid global adoption. One of the most significant factors in the radio’s success was undoubtedly its ability to operate outdoors or whilst on the move, because of its use of small batteries.

This made it very popular with young people everywhere and also in developing countries where access to power from the grid could be unpredictable. The radio’s portability was due to its use of transistors, which drew much less power than tubes and valves used in other radios at the time, making it possible to operate on batteries. Audio quality on small transistor radios was at best patchy. A new device that appeared in the early 1980s, the portable cassette player, was to change this. Greatly improved audio was delivered through lightweight headphones, making it a global success. Its operation was entirely reliant on small batteries. Successors to the portable cassette player now play digital audio and relay video content and are also dependent on batteries.

Walk and talk

The first portable devices that could be used to communicate from some distance while on the move were two-way radio transceivers. They were initially designed for the military during the Second World War and known, naturally, as "walkie-talkies". References to mobile telephony technology could be found occasionally in some science-fiction films before the first mobile phone was marketed in 1983 for a mere USD 4 000. It weighed a kilo and took some 10 hours to charge sufficiently to enable users to talk for 30 minutes. Today, mobile phones are ubiquitous, the fastest selling device ever, with global connections expected to reach 6 billion in mid-2012. Penetration rates of 130% in Europe and in excess of 50% in Africa allow billions of people to be connected without fixed lines as well as to access the Internet, data and multimedia content and, for the most advanced phones, other functions.

Computing on the move

In the late 1980s, portable computing was just emerging in the form of fairly heavy machines that cost thousands of dollars. Generally they had poor displays and a very short battery life. However, following the assumptions of the so-called "Moore's Law" which infers a doubling in semiconductors' performance every 18-24 months, the specifications of portable computers improved dramatically. The sale of what have come to be known as notebooks or laptops outstripped that of desktop machines in late 2008, thanks to falling prices, improved performance, the incorporation of sharper and less power-hungry graphic displays, and longer battery life. The arrival of so-called post-PC tablets in 2010 gave a new impetus to the portable computing market with sales of such devices expected to surge by 98% in 2012 to reach 119 million units, according to an April 2012 report by market research firm Gartner Inc.

Shared connection

With the availability of digital content, the features offered by these devices tend to converge: so-called smart phones can not only make calls, but also play audio and video content as well as accessing the Internet; the same applies to notebooks or tablets.

Countless other mobile electronic devices, such as portable navigation systems, gaming devices and digital cameras also rely on batteries for their operation. This is true too for industrial or home equipment such as cordless power tools or gardening appliances. With operation or talk time being a major selling argument, battery performance is very important. IEC TC 21: Secondary cells and batteries, and TC 35: Primary cells and batteries, prepare standards for all batteries. Primary batteries are non-rechargeable and must be disposed of once used; secondary batteries are rechargeable..

It's all about chemistry…

Since batteries are assemblies of electrochemical cells that convert stored chemical energy into electrical energy, their composition is of prime importance. It determines their performance, characteristics, applications and costs. Batteries used in portable devices are of the dry cell type.

Primary batteries are still the main source of energy in many portable devices – such as small transistor radios, or watches that draw relatively little current – in which they don't need replacing too often. They can generally be stored for a long time and have a low self-discharge rate.

Secondary batteries are needed in equipment that requires a lot of power: in power tools or connected devices with sharp displays, such as mobile phones, notebooks or tablets. They have lower power density and are more expensive than primary batteries, but are cheaper to use in the long run as they can be recharged.

TC work

International Standards for primary cells and batteries, in particular as regards "specifications, dimensions, performance and guidance on safety matters", are prepared by IEC TC 35, created in 1950.

Batteries are designated by a capital letter, with the letters R, F and S defining round, flat (layer built) and square cells, respectively. For certain types of cells, these letters are preceded by an additional letter which indicates their electrochemical system. Letters are followed by a number that gives the nominal cell dimensions and maximum battery dimensions.

TC 21 was established in 1931 "to prepare product standards for all secondary cells and batteries". Its SC (Subcommittee) 21A was set up in 1965 "to prepare product standards for all sealed and vented secondary cells and batteries containing alkaline or other non-acid electrolytes".

The dimension and designation of many types of primary batteries set by TC 35 has been adopted for a number of secondary battery types too. For instance so-called penlight or AA disposable or rechargeable batteries have IEC designations such as R6, LR6, HR6 or KR6 or others, depending on their electrochemical composition. However, many batteries for portable devices do not have standardized dimensions and are often built into the devices.

Both TCs work on standards based on the characteristics, test requirements and safety of the different kinds of battery.

Market prospects

The portable power sector will continue to expand at a healthy rate over the next few years, according to a June 2011 report by Pike Research, a market research and consulting firm on global clean technology. Global revenues are expected to grow from USD 20,3 billion in 2010 to USD 30,5 billion by 2015, a CAGR (compound annual growth rate) of 8,5% that will outpace that of the stationary and automotive battery sectors. The portable power segment will make up 55% of the global battery market, while the other two types account for the balance.

Most of this growth will come from the secondary battery market as TC 35 itself notes that "the primary battery industry is currently marked by relatively flat growth" as it "must increasingly compete with other power solutions, particularly portable secondary batteries".

No Moore's Law for batteries…

The spectacular growth of the mobile consumer electronic market will continue to be the main driver of the demand for more portable power. However, if Moore's Law concerns semiconductors, it has been noted for years that it doesn't apply to the performance of batteries which, while greatly improved in recent years, is still playing catch up in meeting the needs of ever more advanced portable devices. The solution will have to rely on even more efficient electronics and significant improvements in the performance of batteries.

Regency TR-1, the world's first commercially produced transistor radio (1954) Regency TR-1, the world's first commercially produced transistor radio (1954)
"Smartphone" of the latest generation (Photo: HTC) "Smartphone" of the latest generation (Photo: HTC)
Tablet computer (Photo: Samsung) Tablet computer (Photo: Samsung)