Reports from the Energy Storage Research Program at DOE have found that “every year roughly one-million usable lithium-ion batteries are sent for recycling”. Knowing when to replace a battery is an ongoing concern and date-stamping serves as only a partial and imperfect solution.
It is important to understand and acknowledge the fact that batteries do not fail suddenly, but rather they follow a predicted decline in capacity losing performance over time. Battery life is governed by usage, not time.
A new battery is rated at a nominal capacity of 100%. As the battery ages, the reserve capacity drops and the battery eventually needs replacing when the reserve capacity falls below a certain level to be defined depending on the application of a battery-powered medical device.
Nickel-based batteries provide about three-years of service; Li-on five. Storage characteristics have also improved. However, under-usage in healthcare is more common than ever, and bio-medical technicians have discovered that many medical batteries that are recycled still have a capacity of above 90%, leading to millions of unchecked batteries being discarded every year.
The date-stamping approach to batteries has several serious flaws:
It does not detect a damaged or prematurely faded battery. Batteries that are used regularly may fade before the expiry date listed on the stamp.
Through this approach, it is also often neglected that even batteries held in storage and are not in use, lose capacity over time.
It is a costly procedure as it does not allow for full battery service life to be used, resulting in most batteries in this system being replaced after less than half of their useful life is still intact. Li-on batteries, for example, often last 2-3 times longer than the date stamp mandates, but also have higher purchase prices making premature disposal even more costly.
By replacing the arguably outdated approach to battery replacement, with a greener, more reliable approach, the future of battery management in healthcare will be increasingly optimized.