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You are here: Home > Current Topics > At your Leisure > 25 September 2006 |
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It's late. All bar the night lights are off in the house. Nature calls. Keen to avoid waking anyone up, you tiptoe to the bathroom. Ten seconds later you're chewing the carpet, brought down by a trailing cable, connecting an iPod or phone to a socket. As you lie there, spitting fibres you think: 'why do these things always seem to need charging?' and 'that's been attached for hours - surely it's charged by now?!' People's dependence on these devices - mobile communication and entertainment gadgets - makes this scenario ever more likely. In this At Your Leisure, we look into the question of how manufacturers ensure that our mobile phones, iPods and laptops have adequate power. What dangers lie in making sure that these devices have adequate batteries included? In mid-late summer 2006, Apple Computers and Dell Computers recalled around six million laptop batteries amid fears that the batteries, made by Sony, were liable to explode. What with our growing desire for longer-life battery power, growing numbers of features in our devices and the sheer proliferation of different devices; is battery failure and physical danger almost certain to increase in future? How long will it be before someone gets badly injured or worse as a result of charging their phone, iPod or laptop? What are manufacturers doing to avoid such disastrous results? |
Firstly, let's look into the battery units commonly used in mobile devices.
For many years portable equipment relied on a power supply known as the nickel-cadmium battery. This was invented in 1899 by a Swedish scientist called Waldmar Jungner. As research into improving the battery went on, a sealed unit battery was developed. But the chemistry in this battery type does not suit today's consumer demand. For a start, nickel-cadmium batteries mustn't be left in charging units for long periods. Also, if the battery is not fully run down (discharged) regularly, large crystals form on its cell plates and the battery loses performance. Energy density levels are not as high as with modern power solutions.
A very recognisable sight - an AA battery. Copyright: Alicia Solario, from stock.xchng.
So while, with some precautions, nickel-cadmium batteries are durable and low-cost, manufacturers began to look for alternative power sources for today's devices. They have looked for a battery that can store more energy at a time (removing the need for frequent recharging) and they have sought to use less toxic metals, as environmental concerns have grown.
In the early 1990s, lithium-ion (also known as li-ion) batteries have emerged as the fastest growing solution for portable devices. Lithium batteries have been developed since the early part of the 20th Century. Lithium was a promising material. It has the following benefits:
So, lightness, good charging and high energy storage capability - sounds ideal for today's smartphones, iPods and laptops? Well, yes, but...
Lithium batteries that you can recharge proved difficult to develop. For a start, lithium metal is highly unstable and could behave dangerously when charging. So the manufacturers tried a non-metallic lithium battery to see if this would be safer for everyday use. So the lithium-ion battery was developed and whilst its energy density potential is slightly worse than with lithium metal, it was thought to be very safe.
Sony Corporation brought to market the first lithium-ion battery in 1991 and since then, the li-ion battery has swept all before it in powering our energy-hungry lifestyles.
To summarise, the li-ion battery has the following benefits:
Crucially, however, in light of the news about safety fears, li-ion batteries have their drawbacks:
Most experts agree that we should not be worried about li-ion battery safety. The recall of 6 million Sony batteries was triggered by a failure rate of one in 200 000. But some commentators believe that we'll risk almost anything in our thirst for more 'juice' in our mobile devices.
Mobile phones now act as diaries, cameras, videos, even games consoles! Now, if they could make a decent cup of tea, then we'd be talking... Copyright: John Lee, from stock.xchng.
What can your mobile phone do? The one on the desk in front of me has the following functions:
How many of these functions will lie dormant over the phone's life is anyone's guess, but phone manufacturers believe we demand them. Use any of them for a long while - a long call, for instance; or a protracted games session - and the battery will run down frighteningly fast.
The widespread nature of li-ion batteries in mobile phones, digital cameras, laptops and other devices, makes concerns over safety a very hot topic. Battery experts suggest that around two billion li-ion cells are produced every year. Manufacturers such as Sony act fast to reassure consumers and protect their brand image. The battery recalls this year are part of that effort.
Dell computers - it was the batteries, made by Sony, in their computers that they feared would be liable to catch fire. A scary proposition! Copyright: Guilherme Silva, from stock.xchng/
So why were these li-ion batteries recalled? Sony says that tiny particles can at times come into contact with parts of the battery cells. The more energy placed in the battery cells, the greater the risk of impurities affecting the cells when the devices are being assembled. If enough microscopic particles find their way in, then a major electrical short-circuit can develop. This makes the temperature rise, which causes what's known as 'thermal runaway'. Flames are then vented through the battery causing likely injury or risk of fire. It's interesting, if worrying too, that once this process starts (as a result of contamination of the battery cell) nothing can stop it.
Manufacturing defects are inevitable. However, they occur so infrequently as to make big news when they happen. Either that or they lead to recalls, as in the case of Sony's laptop batteries for Dell and Apple. This should be a source of reassurance for consumers. Manufacturers do not want to suffer the financial costs of recalling such a large number of devices.
But the way in which we look after our devices' batteries can also contribute to product failure and safety hazards. A faulty charger can destroy a battery's protection circuit. And when a mobile phone's battery reaches the end of its life and needs replacing, consumers should only use a brand named replacement. There are examples of non-brand (cheaper) batteries 'venting with flame' while charging in a car.
Safety is even more critical when replacing laptop batteries. The hazard of thermal runaway is so much greater than with a mobile phone, that manufacturers secure their batteries with a code that will only be recognised by the relevant computer. So with laptops as with phones, it's wise to only replace a dead battery with a brand name unit.
The speed with which the li-ion laptop batteries were recalled shows that the fault would lie with the manufacturer of the battery and the device manufacturer. In fact, in law, claims would be able to be made at any step in the distribution chain. Sony, Dell and Apple action was an illustration of the seriousness with which they view product safety. The cost of the recall has been estimated to exceed $400 million.
It is true that safer li-ion batteries exist, but with failure rates as low as those given by manufacturers, would consumers be prepared to pay more for the overall device? And would manufacturers be prepared to invest in the alternative? The shrinking battery size in many modern devices, contrasts starkly with consumers' demand for (or manufacturers' supply of) greater functionality.
So, this is a very modern story of the balancing act that consumers and manufacturers perform in their desire for increasingly sophisticated gadgets. The scare caused by Dell and Apple laptop batteries may disappear fairly quickly. But its costs to the manufacturers and their suppliers may mean that in future, battery makers will focus on product safety as much, if not more than, our appetite for energy.
