Powering Wearable Devices: Addressing Power Demands On The Go

Contributed Commentary by Michele Windsor, Ultralife

July 27, 2018 | The medical and military fields are among the leading professional sectors for investments in research and product design, which is reflected in the manner of devices that are becoming available.

For example, portable devices such as nebulizers or infusion pumps and wearable devices like endoscopy recorders or blood pressure and glucose monitors are only a few of the technologies that are now available to the public.

The development of wearable medical devices is aimed at reducing the length of patient stays in hospitals and the associated costs. The continuous flow of information provided by wearable patient monitors can also lead to earlier detection of problems and can result in better clinical results.

While the benefits of these devices are obvious, their design has brought to light several technical challenges, one of which is the continuous tug of war between reduced size and weight and suitable battery life. Reliability and safety are other key issues which need to be considered when designing, testing, and manufacturing battery-powered wearable medical devices.

Wearable devices also pose a challenge for OEMs designing equipment for the military, as interconnected and portable devices have become more desirable for soldiers on covert operations. This is because wearable technologies enable soldiers to be tracked with greater accuracy, making it easier to monitor the safety of soldiers and reduce the risk of errors.

As these technologies continue to advance, OEMs need to consider the power source of their device to ensure it is combat-ready, especially as failure to deliver reliable equipment—depending on the mission at hand—could risk a soldier or patient’s life.

Wearable Characteristics

For the medical industry, as batteries get smaller to accommodate the trend for smaller and lighter devices, we begin to see some trade-offs. The lithium-ion (Li-ion) cells that make up the majority of these batteries have a limited gravimetric and volumetric energy density and, subsequently, wearable devices inevitably suffer from inadequate runtime. If your smart phone runs out of juice then it is inconvenient, but if the same device is monitoring your health then it is far more concerning.

This reduction in battery quality is a real concern. The lifespan of a typical rechargeable consumer Li-ion battery averages around 300–500 charge cycles before its capacity drops to an unacceptable level. Because medical devices outlive their batteries they tend to use removable rather than embedded batteries.

To combat this problem for wearables, OEMs can integrate a credit-card sized battery. Today, these batteries are being used to power devices that are worn by patients, monitoring their health or providing medication when the patient requires it. Being removable means the battery can be hot swapped for another when charging is required, and the device does not need to be returned to the manufacturer for a battery replacement when the original set of batteries reach end of life.

With dependence on wearable devices likely increasing, OEMs must supply consumers with reliable devices that they can depend on. For the device’s power source to be as reliable as possible, OEMs should consult battery manufacturers with extensive experience in their market, as early as possible in the design process. This ensures that OEMs receive a battery that is safe, reliable, and suitable for the device they are powering.

The next ten years will be fruitful for the development of both medical and defense technology. With different applications being developed every day for the wearable market, battery research and development will continue to innovate to power these critical devices.

Michele Windsor is global marketing manager for Ultralife Corporation. Ultralife is an international battery manufacturer, with operations in North America, Europe, China and India. Through strategic growth and acquisitions, the corporation has expanded beyond its commercial and military battery business to include custom engineering design and services, tactical communications systems and a wide range of power accessories for global government and defense markets. Michele can be reached at michele.windsor@ulbi.com