Coin cells in the era of untethered wireless devices

December 02, 2013

Bernard Cole-December 02, 2013

In a recent column titled “The dumbest thing I never did,” Jack Ganssle looked at the market numbers that the ARM architecture has generated and regretted that he did not invest in the company years ago when he had a chance. However, the companies I kick myself for not investing in are the ones who manufacture the small dime-sized coin cell button batteries that power most mobile phones and portable embedded electronics devices.

Even though it's been slow taking hold (like 10 years), the era of ubiquitously connected sensors and embedded devices (aka the “Internet of things”) is beginning to kick in. So maybe I still have a chance to make a killing on the stock market investing in firms involved in making those dime-sized powerhouses.

Even with all sorts of energy harvesting techniques, such devices will also incorporate the use of powerful and smaller batteries. And compared to the use of these batteries in mobile phones and embedded consumer products now, the number that will be needed in our ridiculously connected future is several orders of magnitude higher. (If any of you have tried to calculate it or seen a good source of such an estimate, let me know.)

Because of their ubiquity now and in the foreseeable future, an important aspect of any embedded developer’s knowledge base is information on how to design systems that effectively use such portable power sources. Included in this week’s Tech Focus Newsletter are a range of articles and blogs on managing power in coin-cell-based battery designs, of which my Editor’s Top Picks are:

Low power MCU benchmarking: what datasheets don’t tell you
Developing power-sensitive, low current MCU designs
Use an MCU’s low power modes in foreground/background systems

In addition to Jack Ganssle's “Leaks and drains,” particularly notable is his “A sneak preview,” in which Jack Ganssle reports on his investigation into the use of the CR2023 coin cell in MCU-based systems. The results may be unsettling to designers who are depending on the long life of coin cells in untethered wireless sensor systems.

“I've been running experiments for 6 months to gain a deeper understanding about building ultra-long-lived battery-powered systems, and will be reporting more results soon,” he writes. “Some of my experiments are quantifying the behavior of the components we use. For instance, there's very little known about how a CR2032 discharges in these ultra-low-sleep current applications, and I've amassed a vast amount of data using some custom tools. The results are surprising, and lead me to doubt that even a ten year life is attainable in a real system.

Stay tuned and check into the Embedded.com site and Jack’s Break Points Blog  for new information that I am sure will be useful to you in designing such systems. (I wonder if there is any way to invest in Jack. The information he comes up will be invaluable in our untethered IoT future!!)

In the meantime, included below are some other articles and white papers that I hope will be useful to you, including:

A testbed for measuring battery discharge behavior
Coin Cells and Peak Current Draw
Measuring Bluetooth Low Energy Power Consumption
Ensuring reliability of portable devices

This is another topic that will be of critical importance to embedded developers who must design in the increasingly power-sparse, untethered, wireless sensor environment in the future. Embedded.com welcomes your contributions in the form of resources you have found and want to share as well as your thoughts and experiences in blogs and design articles for the site.

Embedded.com Site Editor Bernard Cole is also editor of the twice-a-week Embedded.com newsletters as well as a partner in the TechRite Associates editorial services consultancy. He welcomes your feedback. Send an email to bccole@acm.org, or call 928-525-9087.

See more articles and columns like this one on Embedded.com. Sign up for the Embedded.com newsletters. Copyright © 2013 UBM--All rights reserved.

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