We are all very aware of how portable consumer electronic devices have transformed our daily lives. It may be a cliché, but none of these portable devices would exist if it were not for the batteries that power them. Here, Neil Oliver, technical marketing manager at Accutronics, explains how designers can future-proof medical devices and their energy supply.
There are many users who will shake their heads in disagreement when told that battery technology is keeping pace with technological development because, at first glance, it does not seem to do that. However, I am sure that even Gordon Moore himself appreciates the technical challenges associated with providing such a large amount of chemical energy in a small space, while ensuring it is safe, reliable, cost effective and reusable.
Today, everyone expects portability in their professional lives as we all strive for greater flexibility and operability. One important area that has seen a proliferation of battery-powered portable devices is the healthcare sector.
There are many reasons for taking an existing medical device and equipping it with battery power, but the most common is the option to carry it around and use it when and where is needed. Whether this is so that the clinician can work more efficiently or so that patients do not need to move from their beds, battery-powered portable medical equipment provides greater flexibility and freedom.
There are many other medical devices that need batteries, but not for reasons of portability. Patient lifts and acute ventilators are typical examples of transportable medical devices that need reliable batteries. For these applications, high voltage and discharge rate capability are the most important performance attributes. Here, medical device OEMs are moving away from the older nickel and lead based chemistries, due to their low energy density and high environmental impact.
The focus is now shifting to specialist Lithium-Ion (Li-Ion) chemistries that have emerged for high drain applications. Li-ion cathode chemistry that utilises a mixture of nickel, cobalt and manganese offers an enviable combination of performance traits such as capacity, power delivery and safety, which makes it ideal for these demanding applications.
Medical device life cycle
The rate of technological change seen in consumer electronic devices over the past decade is truly staggering. The rate of change is, however, a double-edged sword and whereas the product life cycle of a mobile phone may be twelve to eighteen months, the service life of medical equipment frequently exceeds ten years.
Although only part of the entire medical device, the impact of component obsolescence and in particular cell supply cannot be ignored. Until the start of this century, battery manufacturers made cells to defined international mechanical standards and device manufactures designed their devices around the cells.
The change occurred after the invention of Li-ion and Li-ion polymer cell technology and the trend of vertically integrating batteries into device manufacturing. This shift has led to the development of customised cells, which in turn has offered medical device manufacturers the option to produce the ideal device for their customers, in accordance with their specifications. Yet the relentless pursuit of smaller devices means that a cell produced in its millions last year may very well be obsolete and unobtainable next year.
For medical device OEMs this poses a real problem: how to use the latest battery technology and still be able to support devices in the long term for the next 10-15 years. The answer is to work in close collaboration with a battery developer that monitors both battery and device trends and can be truly unbiased when advising customers on cell selection.
Li-ion battery technology allows medical device OEMs to free devices from mains electricity supply and offer clinicians and patients the flexibility and freedom that they experience with consumer devices.
If attention is given at the outset to the future developments in cell technology, then it is possible to design a battery platform that can be continually upgraded over the product life cycle of the device, even if it might not quite keep up with Moore’s law.