A designer's headache
Neil Oliver of Accutronics considers the implications of advancing consumer technology for designers of medical devices that rely on battery size reduction.
At the end of March, Sataya Nadella the new CEO of Microsoft gave his first keynote speech only 52 days into his new role. Speaking at the company's Cloud conference, he expressed Microsoft's vision for mobile and cloud computing moving forward. It was a bold but necessary step. Microsoft's ethos of traditional fixed-unit computing has struggled to compete in recent years with the sheer intensity of competition offered up by the likes of Apple, Samsung and Google. Rapid innovation of powerful mobile operating systems, that offer more portable productivity solutions, has left the software giant reeling.
The trend towards mobile devices is nothing new. Having experienced a seismic shift, the industry has gained momentum in cycles over the last twenty years. We have now reached a point where mobile users outnumber desktops, laptops and Internet users, combined. However, there are drawbacks to such fast paced innovation. The traditionally linear product development has morphed into a vicious cycle of ever increasing consumer expectations, in conjunction with an increased competition to reduce the time to market for each device-iteration.
This has left designers scratching their heads. Design objectives that seemed impossible to implement only a few years ago, are now the norm. As a result, user expectations are getting higher and higher. As customers we want bigger screen sizes, with higher resolutions, packed into thinner, more lightweight devices, with lower price points and long run times. This is as true in the world of professional batteries for medical devices as it is the consumer environment.
In a typical product development lifecycle, industrial and product design consultants are drafted in at the concept stages. The consultants usually specialise in areas such as ergonomics, electronics or even manufacturing readiness. The power solution, in the form of the battery design, is often an afterthought in this process. Because ergonomics and manufacturing have taken a front and centre seat in meeting consumer requirements, the consultants brought in don't always have the most up-to- date skills in battery technology. It is for this reason that, whilst device design has moved forward, design engineers often struggle to meet the ever tightening requirements for batteries.
Limiting the options
However, by relegating the battery solution to an afterthought we risk limiting the options available to designers, making a battery that is truly fit for purpose less likely. By limiting the volume, thickness, weight and material availability, OEMs may have to compromise in other areas. These variables can directly influence factors such as cell selection, robustness, runtime, efficient operating temperatures, reliability and total life. Not considering these issues at the design stage could spell disaster in the long term.
The first consequence is as a result of shaving millimetres off the device and thus battery size. For instance, single-cell Lithium-ion batteries in consumer devices such as phones and tablets are being encased in increasingly thinner packaging. This means that accidentally dropping your phone could rupture the battery casing, causing a short circuit. Although extremely unlikely, this could cause the battery to heat up and even explode.
Although an extreme example, a more likely consequence in a medical device would be an inefficient discharge rate at low operating temperatures. Medical devices used outdoors by rescue teams are a prime example. Whilst OEMs seek to market their devices as capable of operating from -20 to +60 degrees Celsius, designers struggle to optimise batteries to perform effectively at both extremes. For example, a battery optimised for low temperature discharge, will struggle to maintain efficiency in high temperatures and vice versa. This also means that accurate fuel gauging becomes difficult, creating a potentially hazardous problem for medical and life-critical devices.
Another challenge is device weight. The consequence of pursuing the thinnest and lightest device is that OEMs ultimately compromise on run-time and battery lifetime. A battery's energy density is directly proportional to its volume and mass. By reducing the weight of the battery, and subsequently its energy, the runtime is lowered. Even Lithium-ion batteries, which offer the highest energy density commercially available, will struggle to cater for customer expectations in this environment.
The easiest solution to overcome these problems is to work with OEMs at the concept stages to build in requirements for reliable and robust battery design. This helps to achieve a good balance between innovative design and battery performance. It's a process that market leaders like Microsoft would surely applaud, particularly given Nadella's focus on mobile first.
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